Here we go again . . . MK4

[Zeeflyboy]

Well you are certainly putting in the attention to detail - hopefully it pays off in the end with a nice and smooth machine.

Good to share your techniques too, always interested in how people approach certain problems or use equipment in creative ways.

[routercnc]

Well you are certainly putting in the attention to detail - hopefully it pays off in the end with a nice and smooth machine.

Good to share your techniques too, always interested in how people approach certain problems or use equipment in creative ways.

Thanks Zeeflyboy. I hope it is smooth, especially the Z axis which needs to be accurate and aligned so that the 4 rails don't bind up.

Some more progress on the long side parts of the Z axis. I finished the end machining on the other side piece:


Then it was over to the lathe to bore the 18mm clearance hole for the ballscrew to go inside. Here is the first one set up and a pilot hole being started at the bottom of the large counterbore:


Worked my way up using larger drills and then removed the chuck and dropped in the final 18mm bit. This has a 2MT on the end so needed MT3-2 and MT4-3 adapters to fit in the MT4 headstock taper:


This went OK but I ran out of travel on the carriage so needed to re-position the work closer to the headstock end. By doing this the 2 'tabs' on the end of the work (which were to stop it sliding under the pressure of the drilling) couldn't be used, so I ran without. I noticed after a while that the work had moved on me ! - so, I drilled and tapped some holes and mounted it directly to the plate, using the strap clamp I'd made earlier. This was much better. You'd think I'd have learnt by now that clamps can't hold work pieces and stop them sliding if the tool pressure is high.


I had originally intended to bore from one end and make it a blind hole. But the drill was not long enough and although I could have bought a longer one I decided it was just as easy to drill from the other side and go right through. I'd just put a nice blanking cap on the bottom to stop the chips going up inside and landing on the ballscrew (it is right next to spindle where the chips will be flying around).

Problem with that was that the drill bit was not quite long enough and left a small ring of aluminium where the 2 holes met (the blank ring about half way down the hole):


I managed the clean it out with my longest a round file and all was well. Repeated on the other part and big holes finished. I checked the ballscrews and they fit without touching the sides.

There is one small tapped hole to put in each of these parts, plus the blanking cap, and then they are done.

________

Spindle Block
Had a great surprise recently. The spindle mounting blank was too large to fit on my machine so I'd called in a favour from someone with a bridgeport sized / type CNC machine. I only asked him if he could machine it to size, then I would do the rest including somehow doing the 80mm bore in the middle. To my delight he gave me this back:




I couldn't have done that on my machine so I was very pleased to say the least! Now it still needs lots of M12 holes drilled and tapped in the side, some M8 in the front (for the clamps), and the bore is at 79 mm, so needs opening out to final size but that has really given me a head start on it.

The M8 and M12 holes are easy to do, just setting up time etc. The bore will need to be done by putting the part on the lathe cross slide and then I'll need to make up a line boring bar which will run between centres using a dog drive off a drive plate. I've seen this done but not done it myself so I might do a practice piece first.

Couldn't resist a quick dry fit just to check it was going to fit together:


edit - just noticed the spindle block is upside down in the photo ! I'll make sure to turn it around before machining the mounting holes in the side.

[routercnc]

There are a few jobs to do on the main spindle housing. Boring pilot holes on both sides of the block:


Then the pilot holes for the M8 taps for the spindle clamp brackets. Spindle block is so big I had to get inventive on the fixture to machine these parts:


Then onto the tapping 16 off M12 taps and 4 off M8 taps - took a while !


Quick assembly check:


Then noticed that some of the bolts were loose on the current machine. Wondered why it had been chattering more recently - was worried the small 15mm profile rails had worn, but then spotted this:


So I had to dismantle the Y axis and tighten them up. 2 bolts had come right out, and one more was loose. The rail has also lost a bolt. I guess that is what happens if you ask a machine designed for wood to plough through endless 20 mm aluminium plate for months on end. Used loctite and tightened them back up. Also doesn't help that on 15 mm rail they use M3 bolts which are very small and you can't put much torque on the heads.

Then onto making the spindle clamps:






Although I've got to bore out the spindle hole on the spindle block, I thought I'd check everything was going to fit together. Aligning first rail to master datum:

(note the rails are slightly too long - have marked them up for gentle grinding back to length)

Dialing in the second rail, ref the first:



Then checking the vertical alignment showed that the 2nd rail was ~0.05-0.1 high towards one end. The large side plates they sit on will need the M12 bolts loosening and knocking round slightly when this goes together for real.


Coming together:


Then discovered a problem! The whole assembly is ~2 mm to big! The plate at the top of the photo should be flush with the side plate but is clearly too high.


Bit of head scratching, and checking the drawings couldn't find anything I'd made which was out of spec. Then checked the profile rail and carriage and they were ~2 mm taller in total than the drawings I'd down loaded from Hiwin. I know it has been mentioned on this site many times but check the hardware before committing the drawing and making the other parts !
Luckily this is easy to resolve, just take ~2 mm off one the side pieces and everything will be back in line again. I'll leave that till later because everything has to be set up to get it all very parallel otherwise the rails will bind.

Onto making parts for the lathe to bore out the main spindle housing to final size . . . more to follow

[Desertboy]

Damned fine work there!

[Chaz]

Agreed, some of the best on this forum IMHO.

[Nickhofen]

Very nice work.

[Lee Roberts]

Looking great, I like the design for securing the spindle not seen it done like that before, I agree that your work is on par.

Look forward to seeing the lathe work, will you be video'iiinngg it as you machine it?