Epoxy Bearing Materials and Method

John McNamara:

Many thanks for the additional practical points which reminded me of the problems I faced when rebuilding my Super Seven. I had the bed professionally ground and remachined the saddle, etc myself. If I had had the advantage of knowing your method then I would certainly have considered it. I didn't record the amount of wear in my case but I doubt if it was as much as 2mm and I suppose that in your case the lathe had simply had a lot of use.

Someone commented on your Antipodean location which reminded me that the late J A Radford of New Zealand was an Araldite exponent.

John,

Thanks for sharing your experience.

What release agent would you recommend using Araldite?

Wonder if I could have used this method to rescue that bronze worm gear I munched on my BH600G lathe?

Geoff - F(censored) wrong date for the dentist. Only two weeks too early! Ah well got me out walking and seeing GD, so not wasted.

Hi OuBallie

Edit:

Hmm Maybe I should not have replied to this after two hours on the plane. I misread your post A worm gear is not a threaded rod!  Maybe epoxy would not stand up to the rolling and sliding tooth action you get with worm gears.

I am sorry I am so late in replying to your thread, I have been in Brisbane helping clear out a wonderful workshop that was set up by a family member. He was a fine mechanical engineer and gunsmith, He loved quality tools, Many times I sat in the shop with him. A workshop is not just hardware..... It represents a life's collected thoughts and aspirations. I will miss those good times.

Re the Epoxy composite nut.

For a release Agent You can use Carnauba wax applied as several layers each one buffed back, or proprietary release agent available form any outlet that sells fibreglass for boat or model building. The main thing is to get an even and thorough coating.

If you are casting around an old screw try to cast the nut at the point of least worn and largest diameter, Remember apart from the thickness of the release agent the nut will be a dead tight fit. It will bind if you cast it on the worn section when you move it to a thicker section.

The sample thread I did was encased in a steel jacket This makes the setup extremely rigid, I think it is a good method The piece of pipe I used was rough on the inside ideal as the epoxy will nit slip, maybe you could rough up the inside of your housing with a grinder or turn a couple of grooves or a shallow thread in it for a certain grip

When designing your replacement nut you could machine a block of steel to the same exterior dimensions and with the same mounting as your existing nut...Or a little bigger if there is room to give a little more room for the epoxy casting. If you can get it a 3 or 4 mm gap would be good.

You may even be able to set the steel block with its clearance hole allowing space around the threaded rod in its working position, that way you will be sure it is on centre. the threaded rod itself may need to be clamped in the correct centred location if it is not rigidly held in its bearings.

As mentioned in the PowerPoint presentation, I did my casting by first coating the thread then after that coat was tacky I inserted it in the piece of steel pipe and filled in the gap left by the first coat and the housing. This will assure the threads are fully formed.

Maybe you have a piece of whit or metric all thread you can experiment with first for a trial. You will find it is a fairly easy job.

Regards
John

Edited By John McNamara on 01/05/2014 17:01:58

Hi Ega

You do not need to use Araldite, I have also used Megapoxy H From Vivacity engineering in Melbourne. Other experimenters have used West system often used by boat builders. I chose to do the test with Araldite because it is available worldwide.

Regards
John