[SCzEngrgGroup]

The lift mechanism in my ATC is currently using linear ball bearings and ground rods. I'm not happy with the performance, and want to switch to a solid bushing. Plain Delrin is nice in many respects, but friction is not one of them. I'm thinking Turcite Acetal, despite the high cost, would be a good choice, as it is self-lubricating, and very low friction. But I've never used it. Have you?

Regards,
Ray L.

[AUSTINMACHINING]

Delrin is too soft imo. IGUS Makes some great sleeve bearings that are self lubricating. They make all kinds to cover chemical compatability etc. I recently speced some for use mostly submerged in water. They will even send you plenty of free samples to try out. They are especially good at low friction under high lateral loading.

[motionman]

Well......yeah....like every major tool builder uses this in material as a bearing surface in their machines. Was not trying to be a smart butt, but most machine tool builders use this material.

[SCzEngrgGroup]

Delrin is too soft imo. IGUS Makes some great sleeve bearings that are self lubricating. They make all kinds to cover chemical compatability etc. I recently speced some for use mostly submerged in water. They will even send you plenty of free samples to try out. They are especially good at low friction under high lateral loading.

"Too soft" is not how I would describe Delrin. My objection to it in this application is it is too hard. In any case, what I'm curious about is how different is Turcite? Delrin I'm quite familiar with, as I use it in the PDB. But I've never worked with Turcite.

Regards,
Ray L.

[G59]

Despite the high cost................don't you think you'd be better off using a bronze bushing with polished rail? Cost would be slightly more but rigidity and durability would be way up there. With a small piece of felt, impregnated with oil lubing the shaft. (Man I find it hard to put this in words. I can visualize what I mean but...........................)

Maybe I'm too old fashioned, but is a simple fix.

BTW, Turcite also needs constant lubrication, or it will wear out quickly.

[bhurts]

Delrin AF would probably be your best bet for making plain bearings. That or bearing bronze. Delrin AF is probably a better choice since it is self lubricating. There is also bronze filled Teflon if you don't mind the high cost and questionable sourcing.

Ben

[SCzEngrgGroup]

Despite the high cost................don't you think you'd be better off using a bronze bushing with polished rail? Cost would be slightly more but rigidity and durability would be way up there. With a small piece of felt, impregnated with oil lubing the shaft. (Man I find it hard to put this in words. I can visualize what I mean but...........................)

Maybe I'm too old fashioned, but is a simple fix.

BTW, Turcite also needs constant lubrication, or it will wear out quickly.

Brass leadnuts are crazy expensive for decent quality. Plastic is more than strong enough, and far cheaper. I understand your felt suggestion perfectly. I also need something for linear bearings, to replace the linear ball bearings, and I'm hoping perhaps Turcite-X would work well for that as well.

Turcite Acetal, by all references I've found, does not require constant lubrication in light/medium load applications, which this certainly it. It is self-lubricating, so an oocassional squirt of oil should suffice. I'm mostly concerned with the hardness and lubricity. I used Acetal (Delrin) in the leadnut on the ATC, and it gets noisy if not kept liberally lubricated. It basically sheds the lubrication very quickly, then gets noisy. I will try UHMW, which I use in a lot of other parts, but I'm concerned it may be too soft, and too prone to distortion under load.

Regards,
Ray L.

[SCzEngrgGroup]

Delrin AF would probably be your best bet for making plain bearings. That or bearing bronze. Delrin AF is probably a better choice since it is self lubricating. There is also bronze filled Teflon if you don't mind the high cost and questionable sourcing.

Ben

Yeah, but the price of Delrin with PTFE is eye-watering....

Regards,
Ray L.

[G59]

Brass leadnuts are crazy expensive

I agree 100%.

The bronze bushing with felt strip I mentioned was for use with the linear shafts. For the lead nuts,I can only go with what you already have selected.

[bhurts]

I guess "eyewatering" price is subjective. At $30.00 per foot for 1" diameter I imagine I could make 8-10 bushings or nuts. That's only 3 to 4 dollars per.

Ben

[engnerdan]

Is Trucite the epoxy like material that is formed/bonded on to the surface of the metal?

I agree with Laksnake in thinking of Delrin as "soft" but maybe "soft" is not the right term. It has a some creep over time and pressure. In my machine building it works ok for a low load bearing surface but high load and it deforms over time.

Check out the teflon lined bearings. Its a metal shell rolled out of sheet stock and has a teflon liner. They are relatively cheap too.

Check out "Extra-Strength Metal-Backed Sleeve Bearings" from McMaster.

Otherwise like was mentioned, Igus "Drylin" bearings are good.

[SCzEngrgGroup]

Is Trucite the epoxy like material that is formed/bonded on to the surface of the metal?

I agree with Laksnake in thinking of Delrin as "soft" but maybe "soft" is not the right term. It has a some creep over time and pressure. In my machine building it works ok for a low load bearing surface but high load and it deforms over time.

Check out the teflon lined bearings. Its a metal shell rolled out of sheet stock and has a teflon liner. They are relatively cheap too.

Check out "Extra-Strength Metal-Backed Sleeve Bearings" from McMaster.

Otherwise like was mentioned, Igus "Drylin" bearings are good.

No, Turcite is a PTFE (Teflon) material, created as an extremely low friction material. Most of its properties are similar to Delrin but with a much lower coefficient of friction. It is used on the sliding surfaces of nearly all commercial VMCs, and is cut from think sheets, and bonded to the surfaces using a special epoxy adhesive. Like many plastics, it can creep under very heavy load (not an issue in my application).

I've actually gotten plain Delrin bearings to work quite well, by boring most of the inner bore to a larger diameter, so only about 0.3" at each end of the bearing makes contact with the shaft, and that works extremely well. Overall, these bushings perform MUCH better than the linear ball bearing bushes I have been using - lower friction, closer tolerance, and quieter. For production, I will probably use Turcite-X instead, which should reduce friction even further (about 30%).

Regards,
Ray L.

[ivans]

Ray,
You really need to look at the Igus bearings very closely. They have a wide variety of polymer materials and sizes and very good technical information on their website. As was mentioned earlier they will send you samples quite happily. The bearings work very well with low cost rods (i.e. not close tolerance). I have used these in applications in the desert on solar tracking arrays that were heavily loaded, subject to extreme temperature swings and not lubricated. I think you'll find them economical as compared to making your own.

[SCzEngrgGroup]

Ray,
You really need to look at the Igus bearings very closely. They have a wide variety of polymer materials and sizes and very good technical information on their website. As was mentioned earlier they will send you samples quite happily. The bearings work very well with low cost rods (i.e. not close tolerance). I have used these in applications in the desert on solar tracking arrays that were heavily loaded, subject to extreme temperature swings and not lubricated. I think you'll find them economical as compared to making your own.

I will take a look at those.

Regards,
Ray L.