View Full Version : BUILD LOG: Here we go again . . . MK4

30-12-2015, 04:57 PM
I've explored the limits of the current MK3 machine and it's time for an upgrade ! I want to cut aluminium more successfully with a better surface finish.

Here is the design so far, generally happy with it but tweaking minor things here and there:


Z axis
Box-Z design clamping the spindle all round. 15mm 4off profile rails and 8 carriages. Went for the single Z ballscrew in the end as couldn't get a twin ballscrew design to fit and give reasonable travel etc.

This is how the spindle clamps, but still keeps the rails aligned:

Y axis
Twin ballscrew driven with box surrounding Z axis. All joints overlapped such that pre-load can be set on rails before tightening. Has 20mm profile rails on 5mm epoxy.

X axis
Twin beam gantry design using 60x100x5mm RHS steel sections. This sits on 16mm open bearings which are on 16mm simply supported rails. Cannot get finance approval for 1000mm profile rails so am re-using existing parts. I'm going to use 6 open bearings per side to get the most stiffness out of it. When the time comes there is only minimal work to adapt to profile rail.


The gantry is driven by twin ballscrews, and I tried lots of layouts to get them syncronised before getting to this one. Still not 100% decided - this one has 5M HTD pulleys 31.8mm dia with 15mm wide belts. To get the link across means bolting 2 pulleys back to back. Also thinking about a single 25mm wide pulley with 9mm belts shared between the stepper and the link across (2 belts per pulley), but need to read up about 9mm vs 15mm belt strength etc.

The energy chains are split down each side. LH side is for spindle power cable, RH side is for stepper power, home/limits, auxillaries, and water cooling pipes. Now that the control box is 24V logic for limits, (homes still WIP), and all cables are shielded I'm hoping that running them together in the RH side will be OK.

Not decided on water cooling arrangement, got several options which I'll post when I finally decide. The current radiator & fan is quite bulky and 'sticks out' where ever I put it.

30-12-2015, 07:17 PM
I've started making some of the parts for the MK4 machine. Thought I'd start with an easy and relatively quick one.
Here is the Z ballscrew lower bearing bracket. The standard bearing bracket is too large to fit in so I've made my own again. I'll re-use the ballscrew and bearing from the MK3 machine which is already turned down to 6mm shaft at the end allow a pretty small bearing to be used. Just needs a new housing to suit the new design:

Laying it out and machining the bearing pocket:

Machining the profile leaving tabs to hold it:

Cleaned it up and set up to cnc machine the M8 pilot holes (note that this is a drill press vice - a proper precision vice is on my wishlist !)

Started the taps off in the drill press (just to get them straight):

Then finished them off in the vice with the hand tap wrench:
Since I discovered these lovely spiral fluted taps there is no going back . . .

Chamfered the thread entry with my favourite snail countersinks, then cleaned out the threads with a bolt:


More to follow . . .

30-12-2015, 08:14 PM
Next part is the Z axis stepper motor bracket.

Laying it out:

Machining the pocket - no adaptive toolpaths I'm afraid so about 1 hour to machine this:

Then the slot for the motor shaft:

Small pocket to clear the boss on the front of the stepper:

Light skim to get a level surface:

Outer profile cut:
I had problems here as I had the tool stick when it was about 10mm into the part. It was on one of the curves (which I think increases the chip load a bit) and I had about 2 seconds to go from hearing the problem developing to the spindle stopping rotating. I cleared the tool and thought I'd got away with it but it had obviously missed some steps as there was a ridge in the part. I let it finish, going easier on the feedrate, then homed the machine and ran some new full depth toolpaths working up to about a 0.5mm offset inward. This made the outer surface 0.5mm smaller all round, but at least it was smooth again. For this part it did not matter so I was lucky.

Machining the bolt slots was pretty quick:

Set it on end and machined the clearance holes for mounting (thought this might vibrate but it was fine):

Skimmed the other side down to get the final 20mm thickness:

That will do !
OK, so it was not 20.00 everywhere . . . !

Counterbored to 9mm deep (DRO coming in handy here to get them to the same depth)

Snail countersink to finish off (love these things, so much better than the star type which are a waste of time):

Done. Worked out OK in the end:

30-12-2015, 09:35 PM
Next part is the Z ballnut bracket. All started well . . .

Laying it out

Pilot holes for the threaded holes:

Skim the surface to level it:

Machine pocket to house ballnut:
(Toolpaths are fairly basic from Cut2D - gentle ramp into material, then a series of simple circles. No spiral option. But it gets the job done.)


Profile machined most of the way through leaving a bit holding it in place:


All holes drilled to size, tapped, then on the very last hole backing the tap out - it snapped ! Aargh!
Tap was 12mm into the part and bashing and picking was not working. Flatten the end off the centre punch so that was no good.

Got some Alum powder (about 3.50 off ebay for 2x100g) and mixed up a solution with hot water:
Then dropped in the part, and you can see it bubble straight away (bottom right hole).
After a day there were lots of black specs and a general browny dust settled onto the part (hole now top left).

But even after a couple of days it had only eaten about 0.5mm groove in the top of the tap. At this rate it was going to take weeks.

I tried a masonary bit (3mm tungsten carbide tipped) on a very low speed in the pillar drill and this gnawed away at it for about 15 minutes. The drill kept trying to wander off into the aluminium at the sides, so I flipped the part over and put the drill bit into the hole hoping this would guide it. It made a sound like it wasn't enjoying it much but I pressed on. After another 15 minutes of drilling I got to within about 4mm of the surface, and then the drill broke and got stuck in the hole. Luckily I managed to get it out. I've since put the part back in the Alum solution. I think another go with a 3mm masonary bit will have drilled the last bit out, but I think the thread might be beyond use. I could probably live without that bolt and use the other 5 but it is annoying me now. I'll clean it out and see what to do. Could enlarge the hole then make a plug with a flange on it and press it in from the reverse side, then drill and tap into that. Probably tap it before pressing it in just in case !

Clive S
30-12-2015, 11:49 PM
After a day there were lots of black specs and a general browny dust settled onto the part (hole now top left).
http://www.mycncuk.com/attachment.php?attachmentid=16989&d=1451510462&thumb=1 (http://www.mycncuk.com/attachment.php?attachmentid=16989&d=1451510462)
I read something about this in an earlier post and I thought it said you had to keep it on a low light to keep it warm for it to work

31-12-2015, 12:10 AM
.... it on a low heat to keep it warm for it to work


Have you tried putting more alum powder in to see if your concentration is too low?

31-12-2015, 09:03 AM
Hi Clive, Komatias,

I'd also read about constant heat but I don't have a hot plate and using the oven/hob was not allowed so I periodically drained some off and topped it up with water from the kettle. It was wrapped in insulating cloths to keep it warm for as long as possible.

I added about 100g of powder initially, and changed the whole lot for a new batch of 150g after a day or so. There was always some undissolved powder in the bottom even with lots of stirring which meant it was saturated at maximum concentration.

It was working, just slowly. I think a hot plate or keeping it fairly hot would give it more chance, I'll see what I can get hold of.

I don't know if drilling with the masonary bit would have taken 15 minutes without the Alum powder treatment or if several days in the Alum had softened it. I'm nearly through with the drill so when I'm next in the workshop I should break right through.

31-12-2015, 09:42 AM
Masonary bits are too blunt. You would also need to spin backwards to aid removal of the tap. I have used special carbide spade drills to remove taps. The only place in the Uk that has them is
Seriously considering stocking some in 2016

31-12-2015, 10:12 AM
Good to know thank you. I'd ordered a solid carbide 3mm drill a few day ago, but these look better still.

31-12-2015, 10:38 AM
Please Don't get me wrong on what I'm about to say has I'm not pulling down what you have designed, it looks and sure will work great. But This design seems an awful lot of work and complexity and extra cost for no major benifit over a fixed gantry design.!

By this I mean the wide Gantry and wasted space at each end mean it will have about the same foot print and give about the same cutting area of Fixed Gantry.
If used Fixed gantry design with lifting Y axis allowing none lifting Z axis meaning minimal Z axis extension, essentialy just tool length would have been much stronger and far simpler design IMO.

Like I say just an observation which for the sake of others thought I'd mention and not pulling down what you are building or doing. It's looking great sure will work great and i'm looking forward to seeing it come along.

31-12-2015, 04:10 PM
Hi Dean,

Thank you for the comments. I understand where you are coming from and I agonised and developed this design over the last 6 months or so, including looking at fixed gantry ( I think you are referring to that blue framed fixed gantry on youtube ?). I looked at different parameters trading this and that and trying to work through all the options. I think this is version 14 !

In the end I'm pretty happy overall with this concept and think it will be pretty stiff. I also thought long and hard about the arrangement of bits to make sure slip planes were in the right direction so that bearings were not trapped and pre-loaded, and that it could actually be built in a particular order without leaving impossible joints to make.

I also wanted it to look as neat as possible so a bit of the design is for aesthetic reasons as much as anything (e.g. curved cover plates on Y axis, metal junction boxes where the energy chains end)

I'll keep you all posted, but this is probably a long build so you'll all have to wait to see if it is any good at the end. I intend to do a few simple cuts on the current machine at different feed, speed, DOC,etc and film them before it is decommissioned. Then do the same simple cuts when this one is complete to compare the finish, sound (when does resonance, chatter start kick in) plus measure the static stiffness.

01-01-2016, 08:39 AM
These arrived recently as an early Christmas present. Another ballscrew for the Y axis, and another pair of 15mm rails and carriages for the Z axis. All the other mechanical and electrical bits will come from the MK3 machine.

I ordered from Fred at BST automation. I should mention how the ordering works for custom orders. Obviously they cannot list every part in every size to I asked for a quote on the lengths I needed. This was a bit less than the website price, which was nice. I was then asked to add various items to the basket which were 'similar' to the parts I wanted. During the checking out I had to add a note to say the actual lengths I wanted, and then wait at the payment stage for Fred to amend the price. I could then confirm the order.

It's a but of a concern that the order shows stock listed parts and lengths, and you have to take it on faith (and Fred's confirmation emails) that the parts you will receive are the ones you asked for.

But I didn't need to worry - everything was exactly the length I'd asked for. They arrived in a cardboard box, not wooden, but it was well packed out.

I immediately checked the ballscrew and it ran dead true to the eye (unlike the previous ones from other sellers which arrived bent). Bearings were a nice fit on the machined ends, and the end machining was nicely done.


Last job was not forgetting to confirm goods received on AliExpress, which then releases the payment to Fred. Note how this is different to ebay. Overall very pleased with my first order from Fred. Would recommend.

01-01-2016, 02:22 PM
Are the ballscrew end bearings any good? The cheap ones I've seen, admittedly >2 years ago, all seemed to be quite poorly made as they exhibited end float, unless you fiddle about adding shims or better bearings. Have they improved?

For you ballnut mounts, I hope your spindle is accurately trammed, else the the surface the ballnut flange mounts on may not be perpendicular to the base within sufficient tolerance.

Looking at your design, I'm fairly sure that the weakest point will be the Y-axis. You've compensated for the small bearing spacing causing racking by using two ballscrews, which is good, however the carriage can still twist about the X-axis when a force is applied parallel to Y, due to the vectical compliance of the 20mm rail bearings. Assuming you got medium pre-load bearings (I hope not zero), their vertical stiffness will be about 274N/um. The cutter is central, so if we assume the force is distributed equally upon the Y bearigs, but in opposite directions, you'll get twice that stiffness as the bearings act in pairs (I think), so 548N/um. Bearing spacing looks like 78mm and about 200mm to the tool tip from the bearings in the Z direction. This means that the deflection at the bearings is amplified at the tool tip by a factor of 200/78 = 2.56. The stiffness of the bearings is therefore effectively reduced by the same factor, so 548/2.56=206N/um. Hmm, too be fair that's a fair bit higher that the ballscrew stiffness (I estimate ~50N/um for the two in parallel) so maybe it wont be dominant.

EDIT: Just noticed that's you've put the ballscrews on the ends of the X and Y carriages, not at the center (of stiffness), so the stiffness will be a bit worse.

01-01-2016, 09:02 PM
Hi Jonathan,

I've not opened the bearing packets yet, but I'm expecting to have to make up a shim like I did last time. I've been able to make them work on the current machine so am not too concerned.

Ballnut mounts:
The spindle is as true as I can get it - note I'm at the mercy of the flatness of the supported rail on X, and on the flatness of the extrusion for the Y rail. Based on things I've made from the MK3 machine I think it will be OK. If not there are ways and means . . .

Double Y ballscrew design went in at the outset because of the reasons you mention - it cannot rack so you can push the bearings closer together. But you are right, and it bothered me for ages, that for loads in the Y direction, where it rotates around X, there is a moment between the cutting tool (reaction) and the ballscrew (input) which is resolved in the bearings. As they are close together this moment is higher, meaning more deflection.
Ways around this are to lower the ballscrew and reduce the moment - I tried between the box sections but this makes the gantry even wider fore/aft. I tried underneath, which is very good for forces, but it would get swarf on it and if it hit a clamp it would be nasty. So it went on top. The mori-seki is like that so that sealed it.

p.s. What did you mean here?
". . .Just noticed that's you've put the ballscrews on the ends of the X and Y carriages, not at the center (of stiffness), so the stiffness will be a bit worse. . . "

01-01-2016, 11:02 PM
Bearings: Ok, thanks for the info - I'll continue to give those a miss.
Mounts: Sounds reasonable.
Stiffness: Understood - I wouldn't say Mori-Seki doing something one way is any reason to copy, as the relevance of their reasoning is unknown. Also I'm not sure my calculation in the previous post is any good, as the bearings are close they probably can't reasonably be considered as points, plus I ignored the position of the ballnut.
P.S: See here (http://web.mit.edu/2.75/fundamentals/FUNdaMENTALs%20Book%20pdf/Precision%20Machine%20Design%20Error%20Budget.pdf) , from page 53.

01-01-2016, 11:34 PM
Well that link is quite read. OK, I think I get what you are saying there. I did initially put all ballnuts in the middle of the axis, at the centre of stiffness. I hadn't though about it in the way the article suggests, it was just an intuitive start point, but the flange on the ballnut means they need alot more space which pushes everything apart.

So the X axis ballnuts are now on the 'front' of the gantry, whereas the article suggest they should be further back in the middle of the gantry. Problem is that they would hit the X bearings and make everything wider which knocks onto the frame and bed. I've only got so much space and I had wondered about an enclosure in the future so don't want to go past the edge of the table with any parts.

The Y axis ballnuts are also on the side plate of the Y axis, not in the middle of the bearings. Again the flange would push them higher in Z, and they needed much more material under the bearing mounts at each end of the ballnut to support them. It all looked too tall when I drew it.

To summarise I think what the article is saying is that because things will twist and rotate, you should put the ballnut in the centre of rotation (that is rotation of the structural parts caused by moments) so that the nut sees minimum binding loads etc. I think that is a good principle to aim for where ever possible, however I think in practice the machine I've drawn will see relatively small loads at the ballscrew due to this deflection causing a radial / binding load on the ballnut and I'm not too concerned.

01-01-2016, 11:40 PM
Are the ballscrew end bearings any good? The cheap ones I've seen, admittedly >2 years ago, all seemed to be quite poorly made as they exhibited end float, unless you fiddle about adding shims or better bearings. Have they improved?

Jonathan the ones I've been getting from Fred are excellent far far superior to those things from Chai in every way. Finish quality and operation, they don't need a thing doing to them. They come sealed in Bags and lubed up inside a box and are light years better.!

02-01-2016, 02:16 AM
Well that link is quite read.

Mm, it's good stuff.

I've only got so much space and I had wondered about an enclosure in the future so don't want to go past the edge of the table with any parts.

I wouldn't prioritize the enclosure over the stiffness of the machine. The 'sufficiently strong' machine in my sig. is currently enclosed with shower curtains and sitting in a paddling pool containing 240L of coolant, in my friend's living room of all places. It's as crazy as it sounds, but it does work!

To summarise I think what the article is saying is that because things will twist and rotate, you should put the ballnut in the centre of rotation (that is rotation of the structural parts caused by moments) so that the nut sees minimum binding loads etc.

I agree that the radial displacement effects on the ballnut will be minimal, but I was still thinking about stiffness - namely that the center of stiffness is (by definition) the point where when the ballscrew applies a force (which can easily exceed the cutting forces), no angular deflection will occur. Prizes for working out how big the effect would be...

Dean: thanks, noted. If I ever design a machine where their form is not a constraint, I'll consider using them.

13-01-2016, 09:25 PM
As I feared the return to work after Christmas means workshop time has significantly reduced. For various reasons I've only been able to get about an hour in there.

But I have been able to get a few sessions on the CAD and this has meant I was able to go over some of the other designs and have one last go at unlocking some of the compromises. The net result is I've developed some of the other ideas and ended up with what I think is a much better design.

Old one for comparison:

Here is the new version:
iso rear
X axis
Y axis
Z axis
Just X axis showing gantry, ballscrews, epoxy (orange), and custom ballscrew floating end as the ballscrews were not long enough to mount the standard floating end.
X axis drive and belt tensioning arrangement
Side View:

The new features are:
Gantry beams smaller
They are now 80x40x5 RHS steel (down from 100x60x5). I'd put too much emphasis on huge sections, whereas with a double beam gantry I could afford to scale them down and still have plenty of stiffness in reserve over a single gantry.
Because they are smaller I was able to re-configure the X-bearings, bring them closer together, and give more travel in X. They are now only 274mm apart which is getting close to my current machine spacing. I was also able to get the X ballnuts at the centre of stiffness, rather than at the ends of the gantry.

Y rails are much lower
With the smaller gantry sections the Y rails are now lower and closer to the tool, as are the Y axis bearings, which all provides more stiffness

Ballscrews lower
As the gantry sections are narrower I was much happier putting the ballscrews on the front and rear faces as there was much less of a bracket required to join them back to the main Y axis, therefore stiffer.
These are now much lower in Z which also puts them much closer to the tool, which reduces the moments, which lowers the forces on the Y bearings and makes the machine stiffer.
I was also able to put the ballnut in the centre of stiffness, rather than on the outer edge of the Y axis. There might be a marginal gain here I really don't know, but it does look nicer.

Y axis bearings spacing
By re-designing the gantry end plates to free up some space I was able to make full use of the linear rail and spread the Y axis bearings out considerably more than before - without losing travel. This should significantly improve the stiffness due to moment inputs when cutting in the Y direction. When coupled with the lower ballscrews there should be a double win here.
In one of my earlier posts I suggested that double ballscrew on Y eliminates racking - whilst this is true for rotations about Z axis, it is not for rotations about the X axis. To eliminate these you could add another 2 ballscrews lower down, but that is not practical (!) so you do still need to space the Y bearings out even with double Y ballscrews. Rotations about the Y axis are dealt with by having the double gantry beams no worries there.

X drive
I've gone with something a bit different here which does not use tensioning idlers. The steppers are on plates which are slotted, and the steppers are also in slots. Between them I should be able to tension the short belt up to the ballscrew, and the syncronising belt across to the other stepper at the same time by pushing the motor off into one corner. Everything is 5 HTD with 15mm belts.

I've decided that there are a couple of options to place the radiator, plus the option just to go for the 'big metal bucket' out of sight. So I'm going to build it and then just see which one takes my fancy. Sometimes you can CAD things too much and get tied up in the last details.

Luckily the new design retains the parts I'd already made so nothing lost. Thank you for the comments made so far, stirring up the doubts I had about some aspects, and making me revisit the previous designs. I think it is all the better for it.

Right, time to start CAMing up some of the parts ready for whenever the next workshop session is . . .

24-01-2016, 09:11 PM
This lot arrived recently.

2off - RHS for the raised X axis sides - seems pretty square and reasonably straight

2off - 80x40x4 RHS for the gantry beams

1off 30x5 flat bar to reinforce the gantry beams where the rails will sit

2off ballnut mounting blocks (~9 each)

And 4off 16mm open bearings to double up on the Y axis to make 4 per side (no photo)

Also, got a bit of time this week end to nearly finish the X axis motor mount / belt tensioning plate:

Laying it out:

First pocket:

More cutouts and slots:

Holes spotted, top skimmed, and profile roughed and finished:

Bought a new 6mm 2 flute 45deg helix (for aluminium) carbide from 'cncpoorboy' on ebay (for about 9) recently and just tried it out.

Very impressed with the finish:

Some work on the drill press:

Need to skim one side and tap the M5 holes for the stepper, then its another one done.

In case you were wondering the slot will hold the head of 2off M8 bolts to stop them rotating whilst allowing it to slide in the slot. On the other side will be a spacer and a bearing guide to tension the belt.

06-02-2016, 10:40 PM
Tiny bit of progress. X axis motor mount / belt tensioner plate finished.

Here is a trial fit of an M8 bolt head in the slot (final part will use an M8 nut):

Also started making one of the bits on the gantry. I snapped a cutter on final the 20mm pass ! Always the worst bit right at the bottom of a deep slot when the chips can't get out. It welded up and I didn't stop it in time.

Luckily I had a spare so finished the cut. Setting up for the holes in the edges.

Clive S
06-02-2016, 10:51 PM
Coming along nicely where did you get that vise?

06-02-2016, 11:21 PM
Hi Clive
Thanks for the encouragement! If I multiplied time taken per piece by number of pieces to make I might get disheartened. So I'm trying not to think about it.
Vice was from Arceuro. It was about 35 and is surprisingly accurate (a DTI along the fixed jaw barely moves) and the base is fairly parallel to the jaw runner surface (therefore workpiece is fairly parallel to bed)
But after first use the thread got swarf on it which went into the nut and it is very hard to turn. I can't get it apart to clean it out so if you get one put a cover on the thread first. It's actually a drill press vice but is working ok for my gentle machining
To be honest I am going to replace it with a precision vice as one of the future jobs needs to be more accurate than this and I'm fed up trying to tighten the screw. Arceuro make some nice ones with ground surfaces all over and antilift jaws. They are also quite low in height which is good. if I buy one and like it I may get another as a pair of vices can be really useful

13-03-2016, 05:15 PM
It's been a while since I last posted and I'll explain why in a moment. I've made a matching pair to the last part, with a bit of finishing off to do:


Reason for the delay is that I've noticed for some time now that even mild cuts are often generating lots of chatter. I think it has been getting slowly worse, and feeling the Z axis around the rails and bearings there is some relative vibration between rail and bearing, especially at the top left bearing, when the chatter occurs.

Problem is that the chatter can quickly lead to welding, and with so many parts to make for the new machine it was time to check things out. For info I have been running these 15mm linear profile rails (classed as 15mm minature) for about 5 years on 3 successive machines, and that they were bought as used from 'fa-systems'.

I stripped the Z axis down and found significant fretting on the rail, especially around the top left bearing:

Luckily I had a second set of 15mm rails (new) that I'd ordered for the Z axis on the new mk4 machine. However, the hole spacing was 5mm further apart on the bearing carriages. I ended up drilling another set of 4 holes rather than 2 extra holes because the holes would have been too close to the existing ones:

I took the opportunity to drill some access holes in the outer plate so I could assemble the Z axis as a unit, and then bolt it on to the Y axis. It's easier to get everything lined up off the machine rather than trying to assemble it bit by bit on the machine:

I then set the first rail off a side datum, and then clocked in the other rail:

Then assembled the Z axis onto the machine:

I trial cut revealed a much improved machine. A 1mm DOC at 900mm/min 12,000rpm 6mm 2f carbide was fine with no chatter.

So is there a moral to this story? Well my rails were used when I bought them so it's had to be sure but for the occasional poster on here who asks about rail size then I will always recommend 20mm over 15mm.

Back to the new machine. As originally drawn it had 4off 15mm rails around a box Z. Although these are used as 2 pairs loaded against each other I did not feel confident in continuing with 15mm rails all round. Luckily I had left space in the Y axis to upgrade rails or spindle size. So it was a simple matter to add pockets and fit in 20mm rails. I've ordered 20mm rails from Fred, and will use the new 15mm rails just as auxiliaries away from the spindle where the loads are lower.

16-03-2016, 07:15 AM
Whilst cutting another new part I used 'feedhold' to stop the machine just to check something was not going to collide. Then I hit 'start' but instead of continuing on a +X direction to the end of the cut the machine moved in +Y. It was about 8mm into a profile cut so snapped the cutter.

Luckily this was in the scrap part of the material so no harm done. I changed the bit, homed, ran it all again. Later on in the same profile cut (in the -X direction this time) it was almost to the bottom when I pressed 'feedhold' again to check one of the clamps was not going to get machined through. When I hit 'start' is again went in the +Y direction. Luckily I had my hand over the e-stop but it still took a chunk out of the part!

I've never had this happen before and haven't changed anything in software, just the Z axis bearing change. Any ideas?

Clive S
16-03-2016, 07:57 AM
Did you by any chance stop it in a canned cycle I have a feeling that it happened to me once.:confusion:

16-03-2016, 12:29 PM
Did you by any chance stop it in a canned cycle I have a feeling that it happened to me once.:confusion:

I don't think so - I'll check the g-code when I get home as I wrote down the line number I stopped it on. I seem to remember lots of X and Y positional commands so probably not in canned cycle? It was cutting out the outline profile to a part which was almost a rectangle.

The last feedhold problem was done on a pass which had tabs on it, but it was about 50mm away from having gone up, across, and down to create the tab and was going in a straight line to the corner. I was about 20mm from the corner going X- when I pressed feedhold. Upon starting it went Y+ as if it thought it had reached the corner.

Next time I'm in the workshop I'll do some air cuts on the same file to see if I pressed the feedhold twice or something . . .

16-03-2016, 09:00 PM
OK, looking at the gcode where I had the 2 crashes (when 'starting' after a 'feedhold') and I can see there are several straight line moves (must be geometry nodes all along in a straight line from when I was creating and changing the CAD), followed by a G2 radius arc in both cases.

I've read about problems with feedhold in arcs so always feedhold on a straight edge. But I was definitely on the straight bit about half way along the top edge when I pressed feedhold. About line 930. It was some way off getting to the G2 ARC at the corner. When I hit start the machine went up in +Y and snapped the tool clean off.

I've loaded the file onto my house PC (hence the DROs are all zero!) Here is the first one:

This time, on the same part, I was cutting along a straight edge at the bottom, -X direction, when I hit feedhold. It had just done line 1060. This time cycle start moved the machine in +Y. I hit e-stop straight away this time and recovered it. However, there was a gouge in the work piece (!). It's cosmetic but annoying none-the-less.

Looking at the gcode shows another set of linear moves, followed by a G2 arc radius at the corner:

I'll go back to the CAD and see if there are repeat nodes in the geometry as a start, but I'm confused by this as I've used feedhold for years and not had this problem. Now twice on the same part!

I went to Mach3 website in case there was a later version - but it's still R3.0.43.066 I which is what I am running now.

OK, the reason for the repeat straight moves is that there are tabs on those sides. Vectric obviously adds those moves in on every pass, but only adds the Z up and over move when the required depth is met. However, I was nowhere near the depth to create the tabs (they are only 2mm high) so that might be a coincidence. So, still confused about what is going on . . .

EDIT2 / side note:
I've had to do a few 'run from here' operations after hitting the e-stop recently. It is probably out of position as it could be mid-step so I've found you need to:
1. Raise the tool right out of the workpiece
2. Re-home the machine
3. Press 'run from here' on the line you e-stopped on
4. It will show you the required resume coordinates in a window. Before accepting these you should jog or MDI to the X and Y positions it shows. If you do not it will try to move straight to that location which could be through a clamp or the workpiece etc. if you are low. This has caught me out a couple of times!
5. Press OK and it will rapid down in Z to the position it got to when the e-stop was pressed
6. Start the spindle (or there is a check box if you use spindle control from Mach)
7. Hit cycle start

27-03-2016, 08:54 PM
Some pictures of the matching 2nd upper end part - cleaned, drilled tapped and finished:

Then onto the next set of parts. Bed cleaned down and a new 10mm plate ready to cut out 4off bracket plates:

Small pockets cut and holes spotted in all 4 parts:

First one cut out:

Last one cut out:

Opening up the light cnc spots with the same 6mm spot drill:

First pair of them cleaned up, drilled out, counterbored:
The counterbore in each part was a bit nerve racking as it is to take an M8 cap head slightly under flush. This means a depth of 8.1mm in a 10mm part, which leaves just 1.9mm left. Although I had my DRO set on the drill press you still drill them blind and need to trust in the gauge not to go all the way through! I guess I could have used the depth stop nuts as a backup.

Second pair straight off the machine ready for drilling:

04-04-2016, 10:44 PM
Finished the 2nd pair off, cleaned up, holes drilled etc.

These are the corner pieces on the gantry-

Not that exciting so I thought I'd also post another way I just tried out of tapping the threads in those parts (well starting them at least) which is much quicker. I started with one of these tapping chucks from RDG tools - designed to either replace the drill press chuck or for use in the tailstock of a lathe. It has a tommy bar and the chuck is free to rotate and slide inside the morse taper housing:

Link below (they are also on e-bay)

Although you are supposed to tap out the existing chuck and replace it with this one I didn't want to keep swapping them over. I'd looked these over at a show so knew that the MT3 taper comes off the chuck leaving a 12mm straight rod - perfect :

Because the 12mm rod was greased I put it inside a plastic bag (to stop the grease going onto the chuck jaws) and then put in lightly in the chuck - just enough to hold it but still allow it to rotate and slide up and down:

Here it is well into tapping the M5 thread:
This takes seconds to do and you can feel the bite / back off and reduce the risk of breaking the tap.

Note that the drill press is NOT powered - I'm using the tommy bar to rotate it manually.

This worked really well, was very quick, and created threads which were perpendicular to the face. I finished them off by putting the parts in a vice and using a cordless drill.

I think the plastic will not last long, it started has started to tear already, so one option is to make a metal adapter tube which is clamped in the drill press chuck at the top, and contains a long bored out 12.05mm dia or so hole in the bottom to hold the greased rod on the end of the tapping chuck. If the bore is a good fit and there is grease in there it should stop the chuck falling out when you raise the drill press.

To have something set up permanently I might even modify a cheap drill press/stand (the ones where you put a mains drill in) to house a long rod attached to the drill chuck - a bit like the Arc Euro ones but their's only goes to about 6mm or so tap size whereas this goes to 13mm.

05-04-2016, 09:15 AM
I cheated a couple of days ago when I needed to tap some M8 holes in a slab of Ecocast I had just drilled. I held the M8 spiral-point tap directly in the drill chuck, and took off the drive belt on the mill (Warco VMC with multi-speed belt drive so easy to do). I could then turn the drive pulley by hand. Light down pressure on downfeed handle, and this was enough to get a good thread started, finished by hand later. For small taps, I have lightly guided them in the chuck jaws and tightened a tap wrench on to the shank (not square) of the tap to turn them. Especially with these easily-driven spiral-point taps, this works ok to get a thread started. But I'll have to have a look at the RDG tap holder the next time I see them at an exhibition - thanks.

05-04-2016, 07:15 PM
Hi Neale,

Yes, done something similar to that by slackening the motor / belt tension levers on the drill press. But even with the belt slack there is still quite alot of friction and it still tries to turn the motor.

To remove the belt on my Warco pillar drill completely takes a bit of time and involves a ladder, a screwdriver to open the lid, and releasing the motor bolts and is not very efficient. It's not much fun for long due to the effort of turning the chuck & motor.

The method above is quick to set up (just a quick adjustment on the chuck jaws) and is then very easy to turn.

One thing I will note is that the tap slipped occasionally, even though I tightened it as much as I could. I don't know if they do a keyed chuck version but that might be better. Maybe a bit of degrease on the inside of the chuck jaws would help. Next time I'll also try a tap handle on the round part of the tap shank as you did.

11-04-2016, 09:48 PM
Bit more progress. One of the gantry end plates was cut out over the weekend:

Tonight I drilled and tapped all the various holes. Couldn't resist a trial fit of a couple of the previous parts:
(Note the tabs on each end still need facing off. I'll wait for the other one to be machined then do them in the same session.)


With the side plates offered up:



Another reminder of what the end sections should look like . ..

I used the tapping chuck again which made light work of the threads. Also discovered I was holding the tap wrong. I had been putting the tap right into the chuck and it gripped on the round shank - liable to slip. Looking at the 3 jaws of the chuck I noticed that it has ridges in the centre of each jaw. If you put the square part of the tap into the chuck these grip the 4 sides nicely, with 2 jaws on the flats and 1 jaw (with the ridge) on one of the chamfers of the square. Hard to describe but just put the square shank of the tap into the 3 jaw chuck and it will not rotate.

12-04-2016, 08:10 AM
This looks like a masterbuild!
I love it when its over complicated ;)

Fancy, funny and fantastic!

12-04-2016, 09:35 AM
Very nice,
Looking forward to seeing this finished.

08-05-2016, 03:57 PM
An update on the next bits on the list - the gantry lower bearing plates. I need to make 2 mirrored parts, here is the first one progressing -

Setting up and cutting some slots. These are to adjust one of a pair of ballnut brackets. I'm going to run 2 ballnuts pre-loaded against each other:

The other holes have been spotted (to finish on the drill press) and the profile cut out. I tried something a little different to try and get the profile size as good as possible. As this sits on the X bearings I want this to be a datum part during the build. The rough profile cut was +1.0mm, then another rough cut at 0.2mm, and finally a finish cut at 0mm. You can see the finish in the photo which is excellent. I'll check with calipers how accurate the overall size came out.

I've yet to drill out the holes on the top, and there are lots of holes required in the sides, but I thought I'd try a quick fit to make sure all was well. No bolts yet just propped together but looks good!

Here is the start of the one for the other end. I had to line this one up using a DTI and get it very accurate to avoid hitting the holes in the donor plate I'm using. I've cut the slotted holes, next up will be spotting and profile:

08-05-2016, 06:44 PM
Also, I'd made a few design changes a while back but hadn't posted them so here they are.

1. Z axis
-Twin ballscrew instead of single
-Main body machined from solid
-Upgrade from 15mm miniature rails to 20mm Hiwin


2. Y axis
-Double ballnuts, one fixed ballnut housing and one floating housing to allow pre-load to be added
-Simpler bracing pieces

3. X axis
-Double ballnuts, one fixed ballnut housing and one floating housing to allow pre-load to be added

08-05-2016, 07:04 PM
Twin ballscrews on the Z :hororr: - should be able to punch the cutter through the work with the motor turned off !


08-05-2016, 07:35 PM
Cheers Dave !

It might do that yes, but it is still one stepper motor so it's not any more powerful than before. Reason for doing it is that it should help reduce vibration as both sides of the Z axis are held when machining, not just one side.

08-05-2016, 08:02 PM
Following with interest ;)

15-05-2016, 10:22 PM
The first plate has now been drill and counterbored:

The second one is cut out:

Spotted and ready for drilling:

The DRO I fitted to the pillar drill works really well for CBs. Although the depth is not critical, it looks nice if they are about the same height as each other. These are the CBs for the M6 bolts, drilled to a depth of 10mm as the thread needs to stick out to get good engagement:

All the top holes are now finished. Then onto a light sanding with well used paper, then green scouring pad to remove the scratches and after about a minutes work they look quite nice:

Another dry assembly fit:

Next job is the tapped holes in the sides. I bought one of these precision vices a while back to hold the work on it's side:

Mine is the second from the top - Precision Tool Vice Type 2 - 90mm wide

But I need to make some special clamps to fit into the groove. Here is some 10mm plate roughly marked out. I should get 4 clamps out of this strip. I'll put the usual stepped clamp triangles under the far end of each clamp initially, but may add a packer piece of the right height instead to make setting up quicker.

20-05-2016, 06:41 PM
Slight change of plan. I decided to use the 10mm plate to make a nice set of clamps to replace the quickly made scrappy ones. I've been using odd bits of aluminium plate that were supposed to be 'temporary' but ended up being used for ages.

There is no hard and fast rule for the dimensions but here was mine:

Here are the 4 small clamps I made out of that 10mm plate:
The came out pretty well.

Now I'm using those clamps to hold the workpiece for the precision vice clamps:

Here is the drawing for them:

Here is one roughed out as a trial:

Looks like it will work OK:

Just need a set of 4, then I can use the vice to machine the holes in the side of the plates.

Anyone else made their own clamps for machining, especially if they have any extra / time saving / novel features ?

20-05-2016, 08:27 PM
Nice looking clamps! I'm about to change the way I cut the kits for eBay, instead of using masking tape to hold them down on the bed I'm going to cut out the 915mm x 102mm (by whatever depth the balsa is, 1.6 & 2.4mm) out of a piece of MDF and then using a cutter twice the diameter I normally use (2mm in this case) rout out 1mm deep the programming so that when I cut the wing ribs or fuselage sides I can send the cutter up to 1mm below the wood to ensure I cut all the way through. I'll be making holding clamps (sorry about all the waffle to lead up to the clamps I'm going to be making!!!) the same shape as single servo horns which I can swivel over the balsa to hold it...going to use some scrap 4mm Ali I've got lying around...hope that makes sense? :)

21-05-2016, 12:36 PM
Hi Neil,

If you mean using a spoil board then I'd agree that is a better way and one that I use as well for balsa/liteply.

Lee Roberts
21-05-2016, 05:51 PM
Nice work on the clamps, always handy to have.

Anyone else made their own clamps for machining, especially if they have any extra / time saving / novel features ?

These always stick out in my mind:


Some solid blocks from the side may come in handy for you, seen in this video:



24-05-2016, 08:14 PM
OK, to conclude making the precision vice clamps.

Here is the first one set up against a backstop datum (a parallel), with the top surface flush with the jaw (using another parallel to get it level - not in photo). This is so I could batch machine the 4 parts without having to zero and set each one up:


By chance the long clamps I'd just made fitted into the slots on the side of the vice so I could hold it down to make the proper parts. For info the slots in the vice are 10mm wide.

I profiled the counterbores rather than using the drill press:

Then the clearance hole. I don't like drilling deep holes with an end mill as they can jam up, but because of the counterbore they were quite shallow and there was no problem:

Because of the datum plate on the vice each one took moments to set up, then a few minutes on the counterbore and hole and job done. Cleaned up the holes and finished:

Works well:

OK, now back to the main project. I dialled in the fixed jaw of the vice:

I needed to drill holes in the edge of the plate so I used the back face of the fixed jaw to clamp to:


Here is the backstop datum so the second plate would drop in without having to zero:

Then I offered up the parts and the holes were in perfect alignment (lower 5 holes in the plate). All was going well and I was really beginning to like this new vice! :

Then I noticed a problem. The outer plate is clearance for an M8, and the end plate I'd just drilled/milled should be M8 tapped which is dia6.8. Clearly they were the same size.

I checked the CAM and realised I'd picked the outer dia for the M8 tapped hole, which is 8mm. The inner circle, then one I wanted, is 6.8mm. This is because originally they were CAMmed for drill holes (so it doesn't matter which circle you pick), but at the last minute I decided to mill with a 6mm carbide to 6.8mm to save drilling out. But I didn't change the geometry so they were milled to 8mm. Aargh!!

OK, what to do!! M10 x 1.5 takes an 8.5mm pilot so I've ordered M10 button head bolts and will tap to M10 instead of M8. My M10 tap was from a car boot sale and did not want to cut so I've ordered an M10 tap from the same place I bought the M8. It is a spiral fluted tap and the last one I bought from them cuts really well and is good quality.

So I need to wait before I can assemble the end plates.

The other problem I had today was going too deep with a 6mm spot drill which clogged it up and jammed, then snapped it off in the part ! My fault for pushing it too far. Now I need to get a carbide cutting removal tool as someone posted in my thread a while back when I broke a tap.

Lee Roberts
24-05-2016, 10:39 PM
Sorry to read about the problems, all part of the fun...I think? Lol

On a positive note, you've got this as the money shot though a:


They look nice and look to be doing the job just right too, nice job [emoji481]


31-05-2016, 08:51 PM
Update time. It soaked up many hours to get back on track. After a lot of prodding with any pointy shaped tool I could find, plus a soak in WD40, I manage to lever the broken spot drill out of the hole. The edge of the hole was a bit damaged where I'd levered against it but at least the hole was clear.

After checking the main part of the hole was still in alignment I bored it out from the 6mm spot size to the 6.8mm pilot, then ran the M8 tap into it. I had to give it a generous countersink to tidy up the damaged surface then all was well again.

I also managed to drill and tap out all the holes in the bottom of the outer edge from dia8 (should have been 6.8 for an M8!) to pilot 8.5 and then used my new M10 spiral flute tap. As per my recent M8 tap this is also a RotoGrip tap and is very sharp and cuts really well. This one was 11.03, which sounds a lot vs the cheap ones but I think it is worth it having used both.

Here is the ebay link:
In case the link expires in the future here is the description:
HSS Ground Machine Tap Spiral Flute M10 x 1.5 Quality Made by Volkel. Germany

The button head M10 cap heads had also arrived so I was able to trial fit those. All looking good:

Next job was to cut the RHS steel beams to size. I was going to mark it out and use the thin grinding wheel on the grinder to cut it but after lots of deliberation decided it was time for a new tool. In the end I went for this one which is the 355mm rage2 saw. This is because it can cut up to 120mm x 120mm which should cover all needs. It has a nice soft start and just drops through the steel with ease. It is also pretty square out of the box - helped by just having a pivot and no slides etc.

The first beam was cut out and offered up. Looks OK. It is about 0.5mm short of the 730mm length as drawn to make sure I could set the end pieces the exact distance apart.

Next I need to cut the 2nd beam to length then I'm thinking about the best way to set the ends the correct distance apart. Current thoughts are to maybe use the CNC machine to drill out the holes at each end in the side of the RHS beam, including a special hole for a hardened dowel locator pin at the far end. There would be a matching locator hole in the triangular brace side plate at the far end to push the dowel through. This should set the far end housing a set distance from the near end housing.

Another option, is to CNC machine 2 shallow pockets into a large sheet of plywood to take the 'footprint' of each end housing and set them the correct distance apart plus have them squared relative to each other. I could just use a tape measure and square but feel like an assembly jig / guide would be nice. Any other thoughts?

01-06-2016, 04:09 PM
That's looking good now, coming along nicely! Sad I know....but I do like to see lots of shiny metal with lots of holes drilled in....note to self, must get out more :wink:

03-06-2016, 08:12 PM
Second beam cut to length using the first beam as a guide:

Decided to use the CNC machine to drill the holes. Here is one of the beams clamped down and being dialled in. Obviously the edge is not very straight but I wanted to get it fairly close:

6 holes at each end drilled and then milled to 6.8mm, plus a 6mm dowel pin hole at the far end:

Then onto the tapping to M8:
Yes I know, ended up with holes a bit close to the edge - they were covered by another part in CAD and did not realised I put them so close to the edge. Will still work, but could have been better.

Then a trial fit. Note that only the front beam has holes in, and these are only in one side. Still lots to do on these bits. It all fits and aligns well but as I suspected would happen when the bolts are tightened it lifts/rotates one end of the gantry about 0.5mm from the flat plane. This is because the RHS is not perfectly flat along the lengths and so the ends are forced to align with the sides of the RHS.

I intend to machine just enough on each edge of each face to get it all square. This could be just the outer 3-6mm or so as I'm hoping the raised bits are on the edge / corners so just knocking these back a bit will create surfaces which are in plane with each other and square. I think that when I tighten the bolts the membrane flat parts will pull up tight to these new surfaces on each edge and everything will be square again.
I don't want to machine to whole surface as this will make the part quite a bit smaller. We'll see how it goes and then I'll repeat on the other one. Maybe should have done this before the holes . . .
but until it was pulled up tight I didnt know how much it would move.

Anyway then I'll take off the triangular corner plate at the far end and machine in a matching dowel pin hole which will allow me to get the ends the right distance apart from each other.

Actually on this note I noticed that the 6mm end mill I used to drill the 6mm dowel pin hole in the RHS actually made a slightly larger hole. Putting a 6mm shank in there showed it to be a loose fit. I suspect the runout in the chinese spindle may be adding 0.05mm all round so 0.1mm larger diameter? If so I'll use a smaller end mill and interpolate the hole but creep up on the fit.

Clive S
03-06-2016, 11:49 PM
Looking very nice ad sturdy.:applouse:

This is how I got my beams sorted I welded 15mm plates on each end and then had them machined parallel and to length. I also had two faces of the box machined to get the box section true so that the front plate could be bolted to the beams true.


04-06-2016, 07:45 PM
Cheers Clive, good method.

Had a go at sorting out the beams today. I set the front beam using the datums I'd left on the bed:

I used some shims to take out the slight rocking on the underside and get a better clamp:

I then started to skim the face of one of the beams taking off as little as possible. I'd hoped this would only need to remove the high spots but in the end I had to machine back the entire face to get back to a level surface everywhere. Probably had a slight twist in it.

Looked good. Actually this is the first bit of steel I've machined on this CNC and I did get covered in tiny showers of swarf. As it is hot today I had a T-shirt on and they were very hot!

Anyway, then I offered it up to the gantry and as I tightened the bolts I watched for any movement - there was none. I tightened all of the bolts then tried to rock the assembly and unlike before it was solid, there was no rocking on the base plates which means success! Very happy and back on track. Hopefully the other beam is just as straightforward.




Looks quite nice although the steel bits will all get painted.

Lee Roberts
05-06-2016, 12:49 AM
Looking good, good luck with the next beam!


24-06-2016, 11:01 PM
Well I haven't moved onto the 2nd beam yet for 2 reasons. Firstly I've decided to do all the work on the first beam and make sure it is all going to work out. Secondly, although the outer face is now machined flat, I realised that the lower face is not flat enough. So I started by machining that square to the outer face (part is upside down):


It now sits properly on the base plate and is square to the outer surface:

I then flipped it over and spotted all the rail fixing holes in the top surface for the rail.

Next up was to add the reinforcement plate on the inside. I chopped 2 bits to length using the new Rage saw - really easy and quick:

I used metal epoxy to glue the strip in having first sanded and de-greased both surfaces. I then knocked them both with my knuckle and the epoxied strip one doesn't ring like the other beam. Although I'd added this strip to give reinforcement and extra depth to the rail bolts it has also helped with the resonance. Might help with the cut finish a bit:


Then opened out the small spots made on the cnc machine and then drilled and tapped the rail mounting holes to M5:

I haven't machined this top surface yet as I will do it as a pair with the rear beam to get them exactly the same. Although they will have 5mm deep epoxy on top to mount the rails on, and therefore don't need to be machined, the 'MDF mould' I'm drawing to pour the epoxy into needs to sit on a very flat surface. I'll show more when I've finished the design of this mould part.

Then a trial fit and it sits squarely on the base plate too now:


There is another bolt to go inside on the lower face, plus 2 holes to drill in the inner vertical face to add another connecting block. Basically the RHS will be supported on all 4 sides so should be a pretty good joint when done. Then the end plate will go back on with the stepper mount in.

Finally, something I wondered about recently. All the spot drills I've bought and used have been 90 degrees. The twist drill is 118 degs so when it goes into the hole it contacts only a 2 points until it gets going which is a bit hard on the drill cutting edges. Centre drills are 60 degrees so same problem. I had a look specifically for 118 deg spot drills on ebay and they only came up on the american ebay site and there weren't that many. I didn't look for long so could be me but are the 118 deg spot drills not popular? Or are 90 deg spot drills designed to give good centering alignment on 118 deg drills?

09-08-2016, 10:34 AM
Other jobs around the house mean slow progress in the build. I've managed to get the second beam machined.



Drilled and tapped the M5 holes. I bought this spiral fluted tap which has different colour bands for different materials. I thought I'd try this yellow one (for steel) and it works really well.

I've sprayed them with a light dusting of zinc galvanising spray (screwfix) just to keep the rust off and make them look presentable. I've found this sticks well to metal and resists scratching. (Note Spitfire languishing in the background :apologetic:)


Next job is to put it all together, shimming if required, then set it aside. Then move onto making parts for the bed.

02-09-2016, 09:21 PM
I've put off assembling the gantry parts for now and moved on to making the bed rail supports. Here is the basic bed structure and the parts I'm making now are the large RHS sections on top of the uprights (highlighted).

First job is the chop the RHS down to the right length. The Rage saw cut through in about 30 seconds, with minimal effort and just a few sparks. The section is 100x60x5mm wall thickness steel so very impressed:


Light dusting of zinc spray to make the marking out/spot drills easier to see:

Dialling it in as best I could - it bumped around a bit when jogging along the edge but I got it pretty much aligned. From memory I think it was within 0.3mm high to low spots.

Then onto spotting all the holes. It is longer than the machine so I did 80% of them, then pushed the part back and zeroed off the last hole to finish it off. Bit fiddly but actually not too much work.

Then onto the drill press to get to work on it:

I had some M6 holes to tap so used a generic spiral fluted tap but it did not feel good. The effort was high and I could see it twisting. In aluminium it was fine, but this was not going well and the thought of it breaking was too much. So off to ebay to get another yellow ring (steel) tap from Europa tool. Tried it out and the effort was much lower. It made short work of the threading, so ~7 well spent I think.

Next job was always going to be a bit tricky as one set of the M5 rail mounting holes was on the radius. I spotted them on the cnc and went very slowly to reduce deflection. But drilling them on the pillar drill was not working - the bit was clearly deflecting away.

So I knocked up a drilling jig:
The existing tapped holes help locate the fixture to drill out the holes on the radius. I drilled the holes in the fixture a very close fit to the bolt diameter so am using them a bit like dowel pins - thought about getting some shoulder bolts but didn't need to in the end. Just tried drilling one of the holes (with a cordless drill as a quick test) and it picks up the spot drill mark and works well. Will do them all properly on the pillar drill.


In case you were wondering there will be 5mm epoxy on top of the rails which will 'fill in' the radius to create a flat surface to mount the rail. For now they are supported 16mm rail, but I've done CAD checks for 20mm linear profile square rail and it will fit fine and just needs a simple interface plate to bolt it to the gantry. But at 1100mm they get expensive so I'm not buying them at this point.

Next up is some simple holes in the side (will do these the 'old way' scribe, centre punch, spot, drill . . . ) and then repeat the whole lot as a mirror image on the other one.

I've also cut up all the vertical supports which go between the rail and the bed:
These need the holes drilling out to around 9.0mm to allow 120mm long M8 bolts to pass right through and into a nut / nut plate in the lower extrusion channel (not shown), bolting the RHS rail and the uprights to the bed in one go. I think this will be better than using lots of little L brackets.

All for now . . .