Here we go again . . . MK4

[routercnc]

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 )




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

[routercnc]

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 . . .

[routercnc]

The uprights have been drilled out to 9mm to allow the bolts to pass through, and the ends have been machined flat both end to give 100mm length. You will notice there are only 7 of them - one was cut slightly short so I need to cut another one.


I've stopped work on the bed rails because tapping on the radiused edge of the RHS was proving to be a problem. The 5mm tap felt like it was going to break when it partly broke through the other side, basically cutting a thread only along one edge. I've got a plan B which is to machine the area out completely and weld in some threaded bosses. More to come on that one.

Back to the gantry. I've been making good use of my new lathe and made 2off ballscrew floating bearing holders. Here is a walk through starting with the drawing:


The part was hidden in here somewhere, just needed to get it out:


Turned the outer diameter to size, then drilled and tapped the M8 hole:


Then turned the part around, but was not confident on parting off the waste so cheated and used a hacksaw (lathe not turning).


Then onto the boring of the internal features:


As mentioned in another thread I bought a pair of calipers to check the critical bore diameter - it needed to house a sliding fit bearing, so I had to get it close. These are ~OK, but the adjustment handle is a bit low quality.


It seems to have a quick release slide facility - don't know if this is intentional or not? Maybe I'll replace it with a nice brass one now I have a lathe.


Here are the finished parts:


Bearing lightly pushed in a bit to check it will work OK:


Onto the adjustable brackets which are made from 25mm thick stock. I had to remove the clamp on the chop saw to fit it. This cut through 90% of it:

Then I turned it around and cut the last bit off:

Took about 5 minutes taking it steady. Very impressed with this saw.

Onto the CNC machine:


First one machined out:


Here it is next to the bearing housing:


Trial fit:



Last job is to counter bore and drill out the 4 mounting holes, then repeat on the second one. This screenshot is a bit out of date but the ballscrew mounts are on the far right of the gantry:

[JoeHarris]

Ahhh this thread stresses me out! It's all toooo nice! Keep it up though I want to see this beut finished!!


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[routercnc]

Cheers guys thanks for the encouragement. The end seems along way off still. Vice is precision vice from ArcEuro trade. About £100 - really nice would recommend it. Can use as an angle plate to square up against parts as all sides are ground

[routercnc]

Link to the vice:
http://www.arceurotrade.co.uk/Catalo...l-Vices-Type-2

130-040-02000, Precision Tool Vice Type 2 - 90mm wide

£104.24 inc VAT

[JoeHarris]

Maybe by mark 4 I'll be this good - v nice


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[njhussey]

It's all interesting!!!....good to see the good as well as the bad...if you want to see ugly ill show some of my stuff 😁

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[AndyGuid]

It's all interesting!!!....good to see the good as well as the bad...

Ditto!
And this novice (little old me) finds your posts very easy and a real pleasure to follow.
Many Thanks, routercnc!

[routercnc]

Brief update. Next up were the plates which hold those bearing holders . . .

Setting it out, drilling out some of the holes and pockets:


Then bolting down through the holes so I can machine around the outside:


Quick trial fit to make sure all is well:


Went OK but broke a bit when I called for an 11 mm DOC instead of 1 mm in the CAM and didn't stop the machine in time.

I couldn't fit the standard ballscrew blocks in under the end of the gantry so am making my own. There will be 4 in total, 2 each side to allow me to pre-load one ballnut against the other to remove the 50 microns or so of ballscrew backlash. Here are 2 of the blocks, with 2 more on order:



I need to machine 45 degree chamfers on the top of the block but don't have an Engineer's vee block


So I machined up a jig with a 45 degree notch:


Here it is in position to show the idea (tabs yet to be filed off):


Then the blocks had to be squared up. There are lots of videos and info on how to do this on the internet so I won't repeat in detail. Great example here:
https://www.youtube.com/watch?v=tW8HNAlUXxU

In the photo below you can see a raw block (right) and the squared up block in the jaws (left). The brass rod is used whenever an un-machined face is against the clamping jaw otherwise it won't sit flat against the fixed jaw. The deadblow hammer is to make sure the part is seated in the vice.


Once squared up I set it up against a backstop (actually a parallel doubling up as a stop - must make something better !). It is now ready to have the details machined into the end such as the ballnut mounting holes. I can't machine the large clearance hole right through the centre because the part is 50 mm long. Even machining both sides its a bit too deep. So my plan is to bore a precise 20 diameter pocket in the end (say 10mm deep), then set it up on the 4-jaw, indicate on that bore to centre it, then bore it out.