Hi John

These days most users have ADSL internet connections so 40MB comes through pretty fast. I could post the low res version if any user has a dial up connection.

Edited By John McNamara on 21/04/2011 01:16:46

Edited By John McNamara on 21/04/2011 01:18:23

Looks like its done already  

Edited By John McNamara on 21/04/2011 14:19:31

Hi Michael
Hi Bernard

It is great to get some feedback. The file has been downloaded many thousands of times. Unfortunately not everyone is a courteous. I guess that is the nature of the internet.

The thread and nut test piece as shown in the Power point has never loosened up. It was only a test piece so it has never seen duty in a machine , however many people have played with it twisting it back and forth….

My lathe saddle is still running on that material between it and the bed without a hitch, the saddle must weigh over 150 KG I have to crane it off. Just for interests sake when I get some free time I am going to remove the saddle and check the actual condition of the material. its been a few years since I did it.

My Heidenreich and Harbeck 21 RO Lathe is similar to but a little younger than this one
**LINK**

Although I have not tried it I do not believe Epoxy composite bearings will work well for high rotating or sliding speed applications.

They work very well for machine tool slide ways. (some new machines come with them) the material is also very good for bedding and grouting parts together after precision aligning them.

Regards
John

Hello EGA

Yes normal lubrication is required. Epoxy being resistant to most (Nearly all) chemicals once it is cured, is not affected by mineral based lubricating oils or water based soluble oil if you use it. If you study the images in the power point you will see I reinstated the original oil pockets in the epoxy material with a die grinder. The lathe has a small plunger pump that is operated by the saddle traverse handle to provide lubrication to the ways.

The lathe I restored was very worn. Once the ways were ground the and the saddle raised to the correct height there was quite a large gap nearly 2mm between the saddle vees and the bed vees. In this case I did not grind any more material from the underside of the saddle I did use a wire wheel to deglaze and clean the vees under the saddle, alternating with thinners and methylated spirit to remove as much oil as possible from the cast iron for good adhesion before applying the bearing material.

When I got the lathe the backlash on the saddle hand wheel was about a quarter of a turn. Once raised to the correct height it was minimal I also checked the leadscrew height and lateral position at the same time and it was no longer bowed. This always has to be considered if you are restoring a lathe bed. If you decide to scrape the saddle to match a reground bed for a metal to metal line contact you have to machine the top of the apron or the underside of the saddle to correct the lead screw misalignment, and much harder… Correct the alignment between the rack and pinion that drives the saddle. Using epoxy bearing material you only need to jack it into position until all misalignment is corrected. The epoxy is replacing all the worn away material.

The jacks are the key…. You can take as long as you like to get the positioning right before you place the material, I set up the cross slide for normal running before adjusting the jacks, this allowed me to adjust the saddle relationship to the spindle axis as well.

After the epoxy was set the shrinkage across the tiny gap between the bed and the saddle is infinitesimal. I did not need to scrape the saddle in after the epoxy was set.

Regards
John

Edited By John McNamara on 28/04/2014 02:04:29

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