Workshop made Acetal / DELRIN Rack & Pinion

[Neale]

If everything else is working fine, then a quick improvement would be to make an anti-backlash nut assembly out of acetal. Make a couple of nuts with some kind of mechanism to close them together - on my first machine I used a couple of bolts with appropriate locknuts to pull the nuts together via clearance and tapped holes in the nuts. Not a perfect solution but something you could put together very easily. At a pinch, you can make a tap for acetal from an offcut of the leadscrew material - no need for hardening for that job. Probably a whole lot easier than trying to get backlash out of a rack and pinion setup - there's a reason why R&P tends to be used only on larger machines where leadscrews are too long for practicality. Looks easy but mechanically there are a few things that can bite you in the bum.

[davo453]

Thank you for the reply, my present set up has Delrin/Acetal backlash nuts these I made by melting the plastic on to some scrap lead screw and machining the resulting mess to fit. It has proven an almost perfect solution in fact and although this machine has run in excess of 1000 hours now they still don't have any perceptible backlash just a little silicone grease occasionally and all has worked well.

It's not backlash that I am trying to eliminate it is rod lash, as you probably know when you spin a rod at speed and when it exceeds a certain length it starts to wip and that causes a bounce effect at the tool. Hence my looking into Rack and pinion and I may increase the size of the machine at some point in the future too.

I'll just experiment a bit I think.

If everything else is working fine, then a quick improvement would be to make an anti-backlash nut assembly out of acetal. Make a couple of nuts with some kind of mechanism to close them together - on my first machine I used a couple of bolts with appropriate locknuts to pull the nuts together via clearance and tapped holes in the nuts. Not a perfect solution but something you could put together very easily. At a pinch, you can make a tap for acetal from an offcut of the leadscrew material - no need for hardening for that job. Probably a whole lot easier than trying to get backlash out of a rack and pinion setup - there's a reason why R&P tends to be used only on larger machines where leadscrews are too long for practicality. Looks easy but mechanically there are a few things that can bite you in the bum.

[njhussey]

I had a little play with R&P a couple of months ago whilst looking at all sorts of possibilities for making a small router. Have a look here it's a good place to design your own gears as they output the result as a DXF or DWG (can't remember which now!!)

Below is a small one I cut out of 6mm thick Acetal as a trial, I think with a 2mm end mill.

[magicniner]

It's not backlash that I am trying to eliminate it is rod lash.

Convert to rotating nuts & fixed screws.