Making Acetal leadscrew nuts the easy way

[SteveP]

Thanks, Zero.

I bought a 12" length of 1" x 1.25" Delrin from McMaster for about $14 (plus tax/shipping). My attempts therefore only cost me about a buck each, so I really didn't mind taking several tries. I would definitely say that "knowing your material" is about 90% of the issue here. If I were doing a large project, I'd definitely first try to make a small nut on junk piece of all-thread or something just to get a feel for it--and make sure I had enough acetal on hand for a mistake or two (or at least be fairly certain I could get more of the same if I needed to).

--Steve

[Toolguy]

I have bought a lot of Quadrant Acetal from McMaster over the years for many projects. It has been continuously high quality and tight tolerance. I have made an EvaNut for the cross slide (y axis) of my surface grinder with it too. It is one of my favorite materials to work with. Highly recommended.

[Beone]

Made 2 yesterday in 1/2-10 for my x-y table. First one made on the actual rod, second one on the end of my homemade tap from the rod, then both chased with the homemade tap. HF heat gun. Enco 1 in white acetal rod. Both work great. The table is much smoother and much less torque to move and backlash appears zero. Much better than the former nuts, frome acetal, cut standard with the homemade tap.
Dave

[rythmnbls]

I'm another convert to the EvaNut, I'm converting a benchtop mill to CNC and decided to try acetal nuts and acme threaded rod instead of ball screws. The X and Y axis are done and are a huge improvement over the original screws and nuts.

X axis just before installation



Y axis



Regards.

Steve.

[MTNGUN]

Very professional looking work there, rythmnbls.

I am attempting to use Evannuts on a ZX45 mill project. The problem I have run into is that they are too tight -- since they are formed hot, then when they cool they shrink and squeeze the acme screw tightly. That's great for minimal backlash but sucks for friction.

I tried the usual tricks -- using one end of the rod as a crude tap, and spinning the nut back and forth on the lathe. That helped but not nearly enough. So I've been letting the mill cycle back and forth all day and night to "break in" the Evannuts. Two of them are now acceptable but the 3rd is taking its sweet time. The high friction definitely limits the top speed of the stepper motors, so the jury is still out for my application.

[Paul Alciatore]

If running them back and forth loosens them, won't they wear in use and develop backlash? I thought they were supposed to retain a zero backlash property for a long time.

Very professional looking work there, rythmnbls.

I am attempting to use Evannuts on a ZX45 mill project. The problem I have run into is that they are too tight -- since they are formed hot, then when they cool they shrink and squeeze the acme screw tightly. That's great for minimal backlash but sucks for friction.

I tried the usual tricks -- using one end of the rod as a crude tap, and spinning the nut back and forth on the lathe. That helped but not nearly enough. So I've been letting the mill cycle back and forth all day and night to "break in" the Evannuts. Two of them are now acceptable but the 3rd is taking its sweet time. The high friction definitely limits the top speed of the stepper motors, so the jury is still out for my application.

[rythmnbls]

I sprayed my "tap" screw with a teflon lube, and froze the nut in the wife's freezer. In my first attempts I found during the initial thread chasing that the screws and nuts get hot from friction and when they cooled they were tight again.

Regards.

Steve.

[dian]

mix up epoxy with graphite pouder, put it on the rod and pour epoxy around it. if you do it on the machine, its even centered properly.

[darryl]

Just adding another idea here. Since I've made and used this type of nut for several years already, successfully I might add, I'm about to try something new for the formation of them. I will cut two discs from the 1.5 inch OD rod I have, then machine up two aluminum cups such that the ID will accept a push fit of the discs into them. With the two cups bolted together, drill or bore a cross hole to more or less suit the diameter of the actuator rod. Then reassemble the cups with the two acetal discs in them and bore that to the diameter that Evan suggested per the diameter of the acme actuator rod that would be used. This is then clamped around the rod and heated to the point where the plastic flows. The clamp bolts are tightened during this process until the cups edges meet, then allowed to cool. When done, you have an encased EvaNut with two mounting holes, a fairly flat package, and the ability to separate the halves and add shims for the desired looseness around the rod.

You would probably need to spray the discs with a coating of some kind to aid in separating the halves after the forming process. I realize that not much will stick to the acetal, but the coating is only a temporary barrier- you might be able to use baking paper for the barrier. Obviously some experimentation would be required with this process.

What makes this look interesting to me is that it would result in a fairly compact mounting package, height-wise at least. I can see that in many instances, this would be important, particularly if you are scratch-building your mechanism and would want it to be compact.

[Hopefuldave]

I wonder if an evaballscrew is possible? Cut the ball track on the screw with a form tool (or an endmill tangent at the lead angle?) then wind a suitable wire in the track ( with bends at 90* to the screw for the ball feed and return) and mould the nut around it. Ok, probably a stupid idea and the nut would need reaming for clearance... But I might just try it when the tuits arrive.

[elf]

The press fit won't allow the acetal discs to fit in the cups once the discs are placed on the lead screw. You'll also need a good jig to hold the leadscrew precisely in the center when applying the clamping pressure. Seems like it would be more accurate to just make two nuts and machine them to fit the cups afterwards.

[twopintsplease]

I'm struggling as well but reading Steve.P on post 177 and then rereading the whole thread , I have been using acetal "C " not acetal "H" and get the same out comes, the nut is very tight, I am in Australia and "C" seems all there is available here ,early on Evan commented to use delrin homopolymer (spelling ?) i am still trying to source some an give it a go to see if I get different results

[garyhlucas]

I've read most of this thread and wonder if anyone has tried this using Nylatron (Molybdenum Disulfide filled Nylon) It is a great bearing material as the lubricant is built in and it is stronger than delrin. Commonly used in bearings and at the ends of large cranes for the tubes to slide on.

[wierdscience]

I've read most of this thread and wonder if anyone has tried this using Nylatron (Molybdenum Disulfide filled Nylon) It is a great bearing material as the lubricant is built in and it is stronger than delrin. Commonly used in bearings and at the ends of large cranes for the tubes to slide on.

I haven't done it yet,but I plan to do just that.I have the Nylatron and a plan to use it,all I need is some spare time.Watch this thread.

[malbenbut]

Can high density polyethylene be used in the same way for making nuts?

MBB