Plastic Nuts

[ger21]

Has anyone used UHMW for their homemade plastic nuts. It seems to be about twice as slippery as Delrin, but is it strong enough. I'm going to try using 2 start 1/2-8 acme rod, and I'm thinking the lower the friction the better. Or what about Teflon filled Delrin. Although it's 3 times the price, this might be the way to go. Any opinions?

Gerry

[HuFlungDung]

So you want slippery nuts, do ya?



I think plastic is too spongy for a "locating" nut on a positioning screw. It might be good for the "anti-backlash" half of a double nut, but I think the best metallic nut you could want would be aluminum-bronze (trade name Ampco18), or else maybe the epoxy cast-in-place-threads might be good as well.

[balsaman]

HuFlungDung,

The delrin nuts work great for wood routers. No backlash and stiff enough to cut wood.

For cutting steel, you are correct, there is some spring in the plastic.

I use home made delrin nuts on my router and can cut wood and aluminum no problem. There is much more flex in the wooden machine than in the nut.

I have access to pure teflon at work but it's 1/8" thick. One could compress some layers between two pieces of aluminum and tap it. Teflon is softer than delrin.

I don't think the friction is a big deal. I would stay with what ever you can find handy.

Eric

[bcromwell]

Anyone know how much the epoxy cast-in-place-threads stuff cost. I don't remeber the product name right now but I look at the manufacures web site and there wern't any prices listed. Ball park would be fine.

What does everyone thing of taking a piece of brass block with a hole in the middle and trying to fill it with the epoxy with the threaded rod in place. Might be a bit hard to get the air bubbles out though.... Or I guess you could machine the exoxy after it dries and fit it into the brass block....

[ger21]

I think you're talking about Moglice. There is a thread in Machine problems and solutions. I believe it would cost me at least $100 for the 4 nuts I need. I was looking into going that route. I also found a similar product, Super Alloy by Phillycast.

http://www.phillycast.com/.

I emailed them about a price and they never got back with me. If the plastic nuts don't hold up for me though, I'll try the Moglice.

Gerry

[chuckknigh]

I'm experimenting with a design of my own. PVC pipe fittings are cheap, abundant, and some are even threaded.

Basically, take a PVC cap and plug, and thread them together. Drill a hole through both ends, and tap them. Epoxy on some metal nuts -- I don't think PVC this thin would stand up to much use.

Now, since the thread pitch of the lead screw and the PVC fittings is different, you can screw or unscrew the PVC parts together/apart, and in doing so, dial out the backlash between the metal nuts.

A side benefit (if it works) is that the nut would be hollow, and I will try using this as a grease reservoir, to help reduce friction. I'm hoping that the PVC portion of the thead will be tight fitting, and act to keep contamination down to a minimum.

I'm going to make one of these tomorrow -- finally got the right size drill bit and tap. :-) We'll see if theory works in reality.

-- Chuck Knight

[speedracer]

For what is worth, I would not use UHMW for anything on a router . It has a very high Thermal expansion rate. It's like a sponge! I think you would want to check into polycarbonate material. This is the best stuff I can find or stability.

until next time

[ger21]

Actually, I made a tap and tapped a piece of Delrin last night. It worked pretty good. It spun very freely with a little lubricant. Then I noticed this morning, after sitting in the cold all night (55-60°) that it got pretty tight. Now as it warms up again, it's loosening back up, so thermal expansion does seem to play a role.

Gerry

[speedracer]

here is a link to some polycarbonate.

http://www.mcmaster.com/param/asp/de...=Polycarbonate


let me know how it goes.


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