Zero Backlash LH Trapezoidal Thread Cross Slide Nut, From Delrin

I have collected several sets of worn-out half nuts to rebuild, and was planning to use bearing bronze and silver brazing, but I'm intrigued by the idea of using Delrin or Ertalyte and gluing the threaded liners into the bored-out half nuts. I just did a bit of googling and happened upon the Loctite Design Guide for Bonding Plastic, which is packed with information on different plastics and how well Loctite products work with them. It looks like Loctite 401 is the best choice for either one, and I think I might just give it a try. It will be interesting to find out how good an Acme thread I can cut in Delrin and Ertalyte (and bronze as well, for that matter).

Interestingly, Ertalyte is Polyethylene Terephthalate (PET), commonly known by the trade names Mylar and Dacron.
 
I love it when a thread demonstrates "not all who wander are lost". I'd love to see a Pepsi challenge between all these different materials and I'm sure you are just the man to do it Doc! I also appreciate that you expect wandering and that this forum has such great members with their own expertise and contributions.

Doc I'd also love to see how you radiused your cutter.
 
Hi C-Bag,
thanks for your kind words.
we are all fortunate to have a place where ideas can become solutions for common problems!


the radius on the cutter was made by by my grinding wheel "corner"
i used the left side of the wheel and held the tool at about a 12° angle for end clearance and ground the bit until i had a small nub and a radius
i turned the tool and gave another 10-12° of top rake
i didn't use side rake, in the traditional sense-
i just twisted the bit sideways, to hollow the back side of the cut

thanks for your interest! :)

(edited for more content)
 
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I have a photo of the OEM nut that came out of the ol' shenwai

IMG_3734.jpg

the threads were quite thin as compared to my counterfeit.

the removal and installation could not have been simpler.
i removed the retaining M6 socket headed capscrew from the cross slide, and simply turned the dial until the nut came out the back side of the cross slide.
i put the newly counterfeited zero backlash nut into place and turned the dial in the opposite direction
when the nut retention threads were visible in the cross slide capscrew port , i put the OEM capscrew back into place
i gave about a 1/8 of a turn past contact as the torque on the M6 capscrew
it felt right!

even with a wearing leadscrew, there is no unintended movement in the nut or cross slide.

talk is cheap, a test was in order.

i selected some dirty old 18mm 303 stainless and decided that parting would be an excellent first test

IMG_3733.jpg

other than needing to recenter my cut off tool,
the lathe parted better than it ever did!!!

the leadscrew is very tight to the new nut, but the dial now has a very nice positive engagement and moves freely to boot!

i'll be doing other testing soon and will post the findings as discovered!

thanks for reading!
 
mikey said:
Nothing like a test to prove a point, Mike. Good job!
Click to expand...
thanks mikey! :grin:
i'll be very interested to see the differences between old and new,
as well as the differences between materials the nuts are constructed from.
 
I've never made a Delrin nut but I know some of the precision ballscrew nuts are made from Delrin so it must be able to hold its accuracy over time. The cool thing is that if it wears and needs to be replace then that is easily done, as you've shown. I also wonder if using a Delrin nut will reduce the wear on the leadscrew due to the really good lubricity of Delrin. You might make this the material of choice for hobby guys, Mike!
 
mikey said:
I've never made a Delrin nut but I know some of the precision ballscrew nuts are made from Delrin so it must be able to hold its accuracy over time. The cool thing is that if it wears and needs to be replace then that is easily done, as you've shown. I also wonder if using a Delrin nut will reduce the wear on the leadscrew due to the really good lubricity of Delrin. You might make this the material of choice for hobby guys, Mike!
Click to expand...
I have replaced many bronze bushings with delrin replicas.
As long as the heat in the assembly is not above 185F , you are golden.
the delrin replicas have survived in harsh environments.
That’s why I tried the experiment !
 
after finding some Ertalyte, i copied the cross slide nut again.

IMG_3742.jpg
IMG_3743.jpg

ertalyte machines a lot like delrin
one difference that is very noticeable is that ertalyte is a bit more springy or elastic than delrin is
when running the tap through delrin, it made chips that get sheared off
ertalyte seems to make long stringy chips that don't seem shear easily
i also noticed that ertalyte springs back when drilling, the holes drilled come out undersize
so you may wish to ream critical dimensions in other assemblies, there was no critical nature to my nut.

it took a couple extra passes with the tap to achieve the same fit as the delrin nut counterpart,
but i believe all things are as equal as i could make them

here is a video of the roughing operations on the ammco 7" shaper


Thanks @RJSakowski for the material suggestion and enlightenment! :grin:
 
Ulma Doctor said:
after finding some Ertalyte, i copied the cross slide nut again.

View attachment 304680
View attachment 304681

ertalyte machines a lot like delrin
one difference that is very noticeable is that ertalyte is a bit more springy or elastic than delrin is
when running the tap through delrin, it made chips that get sheared off
ertalyte seems to make long stringy chips that don't seem shear easily
i also noticed that ertalyte springs back when drilling, the holes drilled come out undersize
so you may wish to ream critical dimensions in other assemblies, there was no critical nature to my nut.

it took a couple extra passes with the tap to achieve the same fit as the delrin nut counterpart,
but i believe all things are as equal as i could make them

here is a video of the roughing operations on the ammco 7" shaper


Thanks @RJSakowski for the material suggestion and enlightenment! :grin:
Click to expand...
Mike,
Thanks for the report on machinability.
I am sure that I share other's views in saying that I am looking forward to your performance comparison on the nut.
 
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