Re: Need help - Lathe Build, trying to understand requirements/limitations
Originally Posted by
guitarchitect
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1) With backlash compensation, will threading go OK, or should I assume that until I do a ballscrew replacement I'll need to keep using my taps and dies? if I can use CNC for tenons, shaping, and some drilling, that will be a huge help and I can always put off threading.
It is possible to do any lathe operation without ball screws. But you do need mechanical backlash compensation to pull that off. I won't go into the details here, but it's possible to do it at relatively low cost.
2) What kind of spindle encoder should I be looking for? I can't connect anything to a shaft, because the lathe spindle is a gigantic hole. Is there a simple approach and a readily available optical/magnet sensor that I can employ?
The least cost and easiest method is to use a timing belt drive to the spindle encoder. You just bore a timing belt pulley to the OD of the spindle and attach it. Then use the same size pulley on the encoder. There are a few more ways to do this also.
3) assuming I can create a reliable zero where i can start and end the CNC, is it reasonable to assume that I could do manual operations by removing the belts? or should I anticipate that i'll need to either (a) get good at Intercon or (b) do turning operations using the MPG? I've been told I "can't do manual turning using the MPG", but some folks are just biased. but maybe without using ball screws that's true?
With any CNC you can set the work zero to anywhere you want.
I don't know what ''intercon'' is.
It is possible to do some simple turning using a MPG. I do that occasionally on my CNC lathe. But for profiling shapes or anything that requires more than a 1 axis move is pretty much impossible.
4) As a worst-case scenario, is it safe to assume that if nothing else I could do profiling with a belt+leadscrew setup? That alone would be worth the effort for me. It takes me two hours to shape a pen, sometimes more.
Yes, it's possible. But rather than using the lead screw, I would use the rack & pinion that most lathes have on the Z axis. Again you would have to provide mechanical backlash compensation.
Starting with a manual 10x22 and then doing a full CNC conversion would not be my first choice. If you want a CNC lathe, then just simply buying one would be my first choice. Most would require a controls retrofit, but that is normally the cheap part. At least you would be starting with a machine that has all of the expensive bits installed and is a much more substantial machine to start with. A Hardinge CHNC would be a perfect size for what you are doing. These are available on eBay from about $1000 and up. There are many other options available also. If you can find an EMCO CNC lathe that be a good option also for your required work envelope, very nice machines. A quick search of eBay shows them from about $800 and up.
Jim Dawson
Sandy, Oregon, USA