Thread: make plastic leadscrew nuts - interesting

Ok, I'll be the dummy. What would you use a plastic leadscrew nut for ?

You're not a dummy for asking a sensible question -

Normal machine leadscrew nuts are typically brass or bronze but eventually wear. Traditionally you can either cut a new one or buy a replacement. However, some guys have worked out a method to thermo-form a replacement that is arguably of equivalent function. As it is moulded on the existing leadscrew it could be said to be more accurate, but may not be quite as strong or have the wear characteristics (but this will depend to a degree on material selected).
Probably personal preference as to whether you would go down this route or not, but it is an option.

Michael

Hey MrPete,

My interest is as follows

Newbie with backlash - havent yet got the skills to make my own metal nut - and yes, I can buy a new one for $58 + postage - but have been paying out $50 here and $30 there and $40 somewhere else ever since I started playing in the shed again - it all adds up - kept a spreadsheet since last June and spent $1500ish on "small stuff" - sandpaper, paint, drill bits, oil, grease gun, grease, digital caliper, micrometer, centre punch, a few books, new hacksaw, hacksaw blades, thread cutters, dust masks, overalls, oil, safety glasses, face shield, Alox grinding wheel, chisels etc etc etc ......................

Time rich, low skill base and shed budget running out so if I can make one as suggested I'd be chuffed. Also it seems like an interesting thing to do and might be useful to have that skill/experience available in the future.

Bill

Hi Bill

All lathes have some backlash. Leadscrew, geartrain etc. Is it a problem?

Roger

Hi Guys,

Very neat ! As it happens this thread has come at just the right time for a project that I have just started. I need to make a leadscrew and nut for an adjuster mechanism for my hight gauge. Its going to use a 1/4 x 20 thread so it will be interesting to see how it works out.

Originally Posted by rogerbaker

Hi Bill

All lathes have some backlash. Leadscrew, geartrain etc. Is it a problem?

Roger

It can be when the cross slide screw has so much backlash it can pull the tool into the work on certain jobs, such as cutting an acme thread. An extra 2mm doc is not generally advantageous.

The other advantage with a plastic nut is that it can be easily replaced again if it wears.

Dean

kept a spreadsheet since last June and spent $1500ish on "small stuff"

Bill I am deeply concerned that such a speadsheet exists. Keep it Quiet! We need a code for this. What if such an item fell into the wrong hands? Around here that could mean that I would be straightening out old nails and old corrogated iron and trying to press round tube into square for projects. Scary stuff.

Yes burner is onto something here.

Almost at the point of setting up a swag at the big B. They virtually know me by name there.

Then there's all the other places I frequent for industrial gear etc....

The local Gestapo would pull me up big time

Hi

Apparently there are different grades of acetal or whatever, some are more suited to this application than others .

I like the idea . For hobby setups it would be ideal as we 'hobby people dont abuse and use our machinery 24 hours a day ........... even if the new plastic nut only lasts 2 years , make a batch of them and just change the worn over to another new nut for 2 more years of use .

Bill, there have been attempts earlier at making spare leadscrew nuts. Using a very high grade, quite pricy reinforced resin called Moglyce. You may have a read at this:
http://bbs.homeshopmachinist.net/thr...h-with-Moglice

Personally, I have doubts that leadscrew nuts made from plain acetal are going to last that long.

Originally Posted by rogerbaker

Hi Bill

All lathes have some backlash. Leadscrew, geartrain etc. Is it a problem?

Roger

Hey Roger,

Its approx 25 thousandths - yes I understand that many people dont worry about it - my own personal finding is that it is a hassle when i pull back check the diameter then go in again and wonder if I've taken up all the slack and check the marks on the wheel - If it was only 5 or 10 thousandths it wouldnt niggle me so much.

I've read that it can be a hassle when parting off if there is a lot of backlash - havent got enough experience yet to know if thats a big deal or not.

Bill

Originally Posted by cba_melbourne

Bill, there have been attempts earlier at making spare leadscrew nuts. Using a very high grade, quite pricy reinforced resin called Moglyce. You may have a read at this:
http://bbs.homeshopmachinist.net/thr...h-with-Moglice

Personally, I have doubts that leadscrew nuts made from plain acetal are going to last that long.

Thanks cba,

I just googled Moglice and downloaded the handbook, thats fascinating. Have been aware of soft plasticcy materials being used to cast flat surfaces and tables for machinery, there is some discussion in threads on this forum, I think the oldest example of that way of thinking would be the Yeomans concrete lathes from WW1 and the concrete home made milling machine proposed by Joe Romig.

For somebody like you how long would it take to make a new leadscrew nut from a piece of raw metal ? Or would an experienced person simply not bother and buy one off the shelf ?


Bill

Originally Posted by steamingbill

Hey Roger,

Its approx 25 thousandths - yes I understand that many people dont worry about it - my own personal finding is that it is a hassle when i pull back check the diameter then go in again and wonder if I've taken up all the slack and check the marks on the wheel - If it was only 5 or 10 thousandths it wouldnt niggle me so much.

I've read that it can be a hassle when parting off if there is a lot of backlash - havent got enough experience yet to know if thats a big deal or not.

Bill

Auch, that is about o.6mm. Not exactly a pleasure to work with. If you cannot feel accurately the point when taking up the slack, then this is because the slide is adjusted too stiff. But this can be a vicious circle, if the slide was adjusted on the stiff side exactly because of the excessive backlash.

Originally Posted by steamingbill

For somebody like you how long would it take to make a new leadscrew nut from a piece of raw metal ? Or would an experienced person simply not bother and buy one off the shelf ?

Bill

I would say it depends on the thread form and if a tap or a threading tool is available. If one has to first grind a threading tool to make a set of halfnuts it starts getting a longer job. I am just a hobby machinist and do not have to put a price on time. But if the item was still available off the shelf (and by weight cheaper than gold **), I would probably rather buy it and use my time for something else.

** I have a case lined up, new cross slide nut for my Emco lathe needed. Its an easy to make small item, the original is a Zinc alloy and I will use Bronze. The item is still availabe off the shelf, but about 50 Euro plus postage too much of a rip-off.