Here we go again . . . MK4

[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.

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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.