'Plastic' bearings?

[The Artful Bodger]

This is a simple ball turner device I made and I have made plastic bushes for the pivot. The plastic is possibly Acetal but I am not sure.

Unfortunately the bushes are too tight and I require a long handle to operate the tool. The shaft is hardened and polished 20mm steel.

How can I loosen these bushes? Would heating the shaft reform the bushes to a looser fit?

Thanks

[elf]

Evan's thread should have enough info in it for this. Without pressure, I think you'll need to get the shaft too hot. Without ventilation, this could be hazardous to your health (especially in California )

If you don't have a reamer the correct size, perhaps an adjustable reamer will give you a good enough id.

[metalfixer]

Maybe try some lapping compound.

[grim_d]

Wrap a bit of sandpaper round a dowel or drill shank and massage them until you are happy. No need to over complicate matters.

[brian Rupnow]

Nylatron is too "grabby" to make good bearings. I've been down that road. By the time you open them up enough to not be grabby, they become too sloppy to make good bearings.

[JCHannum]

Plastics have been used for years as bearings. Proper selection for the application is necessary as with any bearing material.

http://www.machinedesign.com/basics-design/plastic-bearings

[Magicniner]

Nylatron is too "grabby" to make good bearings. I've been down that road. By the time you open them up enough to not be grabby, they become too sloppy to make good bearings.

For what applications and at what speeds?
I've seen Nylatron used to very good effect and with excellent life for the wet end of model boat prop shafts and have used it for bearings in hand operated equipment greased or lightly oiled on assembly.
On the other hand if you tried to use it for moderate to high speed shafts dry it may well grab or eat itself.

- Nick

[Toolguy]

With the bearings pressed in their holes, use an on size reamer or .001 oversize to ream the plastic bushings and they'll be fine. I made one the same way with Acetal bearings and it works very nicely. Heating probably will not work out well.

[brian Rupnow]

I tried to use Nylatron as bearings for a hit and miss model engine (Kerzel). It was a total failure. I had thought it would work great, because that stuff is slipperier than goose snot. Once you got the shaft turning, it exhibited a low coefficient of friction, but if the engine sat for five minutes it took a lot of force to get the shaft turning again. Like I said, it seemed very "grabby".

[Illinoyance]

If you only need to take out a thou or two blue the ID with a sharpie. Use a very sharp triangular scraper to remove the blur plus a little plastic under the blue. The blue is just there to show where you have scraped.

[Mcgyver]

How can I loosen these bushes? Would heating the shaft reform the bushes to a looser fit?

assuming typical construction - ie the bushes are pressed into a hole, use an adjustable reamer to enlarge that hole. Same principal with sintered bushings, you control the ID of the bearing by the size of the hole they're pressed into.

[wombat2go]

About 2 years ago I made a stem seal out of acetal for a vintage faucet in the shower.
I bored it to a tight sliding fit on the stem.
In all that time , it still has "stiction" like Brian mentioned, at the first part of rotation, then it frees up.
No leaks so far.

[wern]

Vesconite, https://www.vesconite.com/ I have used this material on bushes where bronze and cast iron wore out, I am sure delrin will work just fine in your application. I think there is a size calculator for ID and OD of the bush before press fitting somewhere on the website.

Werner

[Magicniner]

I tried to use Nylatron as bearings for a hit and miss model engine (Kerzel).

Yes, I expect it's unsuited to I.C. engine bearing applications, I'd never thought of trying it for that ;-)

[Magicniner]

About 2 years ago I made a stem seal out of acetal for a vintage faucet in the shower.
I bored it to a tight sliding fit on the stem.
In all that time , it still has "stiction" like Brian mentioned, at the first part of rotation, then it frees up.
No leaks so far.

If you'd used PTFE and a polished shaft you'd have had a functional stuffing box and no stick.