Zero Backlash LH Trapezoidal Thread Cross Slide Nut, From Delrin

machPete99 said:
In a recent post on PracticalMachinist someone said they replaced crossfeed nut with delrin and fount that knurling operations did not work as good:

Which method to reduce cross-slide backlash?

About 1/2 turn (60 thou) backlash on a Sheldon I've just brought "online". The screw shows light/reasonable wear on visual inspection, and backlash is about the same even at the far end of travel where there would be zero wear; so the bulk is in the nut. Machine a new bronze nut? No acme...
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That’s one of the things I was thinking of. Their will be alittle smoosh maybe which will give you movement on the slide.
 
 
machPete99 said:
In a recent post on PracticalMachinist someone said they replaced crossfeed nut with delrin and fount that knurling operations did not work as good:

Which method to reduce cross-slide backlash?

About 1/2 turn (60 thou) backlash on a Sheldon I've just brought "online". The screw shows light/reasonable wear on visual inspection, and backlash is about the same even at the far end of travel where there would be zero wear; so the bulk is in the nut. Machine a new bronze nut? No acme...
www.practicalmachinist.com
Click to expand...
I've not done any Knurling yet, but my impression is I'd not do the pressure style Knurling and go for the clamp style just so it wouldn't cause so much pressure on the crosslide and headstock. Doc's crosslide nut sure looks substantial compared to some I've seen. Still, very interesting to see how it goes.
 
I did an "EvanNut" on the Y - axis of my cheap X-Y table, still need to do the X - axis but it seems pretty strong. I can see how knurling might be a problem in the op's situation though.
 
RJSakowski said:
Delrin has a very characteristic odor when it burns. UHMW will smell more like candle wax. Ultem and PEEK have very little odor although Iltem is a characteristic transparent amber color and PEEK is an opaque beige color. Another plastic which has better mechanical properties compared to Delrin is Ertalyte (PET-P).

I find a burn test to be one of the best ways to identify plastics. Rather than an open flame, I use a soldering iron. It helps to build up a library of known samples to test against.
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Thanks RJ. That's very helpful unlike the quick stuff I can find. Can you explain why Ertalyte (PET-P) would be better than Delrin for this particular app? The only plastic I'm somewhat used to is UHMW. Turns out you can even get chunks of Ertalyte (PET-P) on eBay.
 
C-Bag said:
Thanks RJ. That's very helpful unlike the quick stuff I can find. Can you explain why Ertalyte (PET-P) would be better than Delrin for this particular app? The only plastic I'm somewhat used to is UHMW. Turns out you can even get chunks of Ertalyte (PET-P) on eBay.
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Here are the data sheets for the two . Ertalyte has a higher hardness, better wear resistance, and a lower coefficient of friction than Delrin. Less water absorption means less swelling and better dimensional stability. A higher melting point. Higher tensile strength. All good things.
 
So bottom line would you use it for lead screw nuts?
 
RJSakowski said:
Here are the data sheets for the two . Ertalyte has a higher hardness, better wear resistance, and a lower coefficient of friction than Delrin. Less water absorption means less swelling and better dimensional stability. A higher melting point. Higher tensile strength. All good things.
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Thanks @RJSakowski ,
I was completely ignorant of Ertalyte until you posted your wisdom, thank you for your valuable information :tranquility:
 
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thank you all who have read and participated in this evolving experiment.

now that i have another avenue to explore, i'll do a "pepsi challenge" between the 2 plastics
i'll be ecstatic to work with another material superior to delrin! (and i love delrin!!!)
 
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i find it interesting that delrin has nearly a 1000lb higher shear strength than Ertalyte
but conversely, delrin has a lower tensile strength
 
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