Thread: Bringing an old Robot back to life - Surface Grinder.

I left out a few details about the wheel adaptors in the previous post while working out how to post the pictures. The pictures show a very accurate method for checking a small internal taper using gauge balls and a few simple measurements followed by a bit of trig.
The taper is 3 inches per foot or 14.250 degrees included angle.

This is the fixture I made for holding the adaptors while screwcutting, boring and grinding the taper.

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A short video of grinding the internal taper

Thanks Techo, I was hoping you would elaborate on that, as I need to make some for my TCG.
But I can't view the video. I get the photobucket page with an empty box where the movie should be.

Originally Posted by Bryan

But I can't view the video. I get the photobucket page with an empty box where the movie should be.

You need to be patient, Bryan. It needs to load most of the video before it starts.... I nearly closed the window too....

Lately I have been working on flanges for the grinding wheel adaptors, these are 1.250" x 16tpi left hand internal thread. I decided to set up my little Hercus Compulathe to cut the threads as I want to make a few of these but I had a little trouble working out which Canned Cycle to use, being L/Hand internal, in the end I basically programmed it as an external R/Hand with slight modifications. It turned out very well as can be seen in the short, low quality video.

Lex.

https://www.youtube.com/watch?v=m1TK...are_video_user

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I need to make a new bronze nut for the cross slide screw as the original has about .070" backlash. This screw is 7/8" diameter x 1/8" pitch Acme, 2 start left hand, so making a new nut is going to be a little tricky.

I have been doing a few trial runs internally screw cutting some scrap brass on the little Hercus CNC lathe before tackling the actual bronze nut so I will post some pictures and a video of cutting the nut in the next few days.

This is a link to a video of the screwcutting operation on a brass test piece., the little machine handled the coarse lead very well, even better than I had expected.

https://www.youtube.com/watch?v=aiXidAxbksc

It was hard to see the actual threads in the video and the first picture here is not much better but I can say that the tool cut very cleanly. The tool is just a piece of a broken #2 centre drill ground to Acme form but most importantly it has the correct leading edge geometry to allow for the high lead angle.

Lex.




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A couple of shots of the new bronze cross slide nut blank being prepared before internal screw cutting.

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The finished nut is now in the machine and it is much better to use with only around .005" backlash as opposed to .070" with the old one. I made a fixture to hold the nut for screw cutting because I didn't want to risk it moving in the small 3 jaw chuck.


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After a long delay I now have 2 new grinding wheel adaptors and some spare flanges, which are easy to make, compared to the actual adaptors. I will get around to making some more adaptors in the future but I have enough to get by at the moment.

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The wheel assembly on the lower left of the picture shows the wheel adaptor that came with the machine, it has right hand threads so requires extra care when in use.

Originally Posted by Techo1

... shows the wheel adaptor that came with the machine, it has right hand threads so requires extra care when in use.

Sounds like it could be a ring-in - I'd be tempted not to use it if the thread is the wrong way around. I made extra adaptors just so I had them if needed rather than having to make ones and twos in the future.

Michael

Originally Posted by Michael G

Sounds like it could be a ring-in - I'd be tempted not to use it if the thread is the wrong way around. I made extra adaptors just so I had them if needed rather than having to make ones and twos in the future.

Michael

In theory you would think that the wheel would just unwind itself and go spinning across the shop but in practice that does not happen or at least it has not happened to me even when almost stalling the wheel by taking too much of a cut.

Nice work. Been watching for a while now. I like the idea of gauge balls (never even heard of them before) to measure the taper. Totally removes the guesswork out of getting the taper correct or even having to test fit to a known taper blank.

I assume that also explains the 3 threaded holes on the arbor, they are purely there for workholding purposes when you were making them?
I am yet to successfully watch your video on your internal grinding of the taper, I assume you have a cylindrical grinder?

Anyway, they look great. I like the idea of fastening the grinding wheel with a threaded flange instead of 3 cap head screws, which is what I currently have. I'll try again to watch the video, according to Joe I need to be patient!

Nope, still cant view it. Says you've moved or deleted it.

Simon

Originally Posted by simonl

Nope, still cant view it. Says you've moved or deleted it.

You mean the video in post 47?
Still there, you just I need to be patient! (well not very patient for me took about 10 seconds)

Techo1

Is that a diamond wheel on the taper grinder?

Stuart