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"Grinding" a small spindle for ABEC 7 bearings


Jun 28, 2012
Mt Clemens, Michigan 48035
I suspect below is a rough idea of your project. What most are saying is that the ID bore that fits the bearing OD should be close to the size and in alignment with both ends so as not to try to twist the bearings..and the thurst shoulder or axial shoulder needs to be square so also not trying to stress the bearing.

Yes, important no matter what style bearing you uses.

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Cast Iron
Mar 20, 2017
Just out of curiosity, what part of the collet system did cataract patent?
The collet was invented in the 1850s and cataract started, like many other lathe manufacturers, making copies of Stark bench lathes.

jim rozen

Feb 26, 2004
peekskill, NY
"The replacements are 7205C-P4-DGA angular contact bearings. There is some ambiguity about whether that will work without a bunch of fiddle besides the fits."

Nope. No ambiguity at all. It won't. Look I understand you wore your welcome out in one forum section and moved to another one. You were a research scientist in a former life - as the great John Stano once said 'don't quit your day job, you'll be all right.'


Sep 14, 2008
Ever hear of Hardinge of Elmira, NY? They produced a famous series of machines for toolrooms and the watchmaking industry 100+ years ago. That series of lathes was named Cataract. The largest was the Cataract 5. All of them were small and would fit your "too flexible" sobriquet. But they were very popular. So popular the whole world still uses the patented collet system designed for them. That's the C in 5C.

You might learn something reading this:

I suppose the first time you picked up a 5C collet, you were full of wonder

"I wonder what the 5 means, and the C, what could that be for?"
"I wonder why it's xx.x" long?"
"Why did they choose that thread, why the 60 deg angle on the thread?"
"So what's special about the angle of the taper on the collet, why did they choose that angle?"
etc etc

And then you did exhaustive research, and after a few hours of reading you are an expert on 5C collets,the size,the angle etc etc. You were probably intrigued as to why 60degs for a thread form, and researched back to the English Industrial revolution and the evolution of machine threads, but that wasn't enough, you did a deep dive into threads, back to Babylonian times.

And know your the worlds foremost expert on 5C collets.


Me, I'm a philistine. My only interest in 5C collets is:

Do I have the xxx diameter I need, and where is it in the rack?


As a research scientist, at some point you have to pull your head out of the sand and wonder where all this research is getting you. When you were doing this is a job, there has to be some ROI.

Maybe the intellectual challenge is the ROI for you. There's certainly no ROI in making that Clausing something it isn't, was never intended to be, and never will be.