Headstock bearings scraping

**gaminn** · 03-02-2021, 11:47 AM

Hi,
I have freshly scraped headstock bearings on my machine. I tried to highlight high spots with blue colour. Please see pictures:

I hope it is good quality scraping. Do you think I can run my machine's spindle?

**gaminn** · 03-03-2021, 08:50 AM

Are the pictures of good quality or is it impossible to judge the scraping quality based on these pictures?

**TGTool** · 03-03-2021, 09:26 AM

I haven't scraped bearings, so consider that against my opinion.

The contact spots seem very meager compared to flat surface scraping. I would have expected to see more blue spots more frequently. I can't tell much about your actual physical technique with the tool, but the photo I have of bearing scraping that impressed me the most had a lot of regular marks showing that the guy had applied the tool in what might be called spiral directions to get the same effect as the 90 degree alternations on the flat. This did show a lot more contact spots but I concede that your photos may not show the actual bearing surface well. A long winded way of saying it doesn't look good to me but I've got a 20 percent confidence in that opinion.

**gaminn** · 03-03-2021, 10:24 AM

Thank for your reply! I have also a feeling that there are not many bearing spots and they are not evenly distributed. Is there any book or any other source where the quality of bearing's surface is described?

**TGTool** · 03-03-2021, 11:33 AM

I'm not finding the saved photo at the moment, but you might look at this video and the one following of scraping in a plain bearing.

A toolroom lathe spindle bearing re-scrape. - YouTube

**Orbital77** · 03-04-2021, 05:33 AM

Originally Posted by gaminn

Hi,
I have freshly scraped headstock bearings on my machine. I tried to highlight high spots with blue colour. Please see pictures:

I hope it is good quality scraping. Do you think I can run my machine's spindle?

It's very hard to say how good the print is but based on what I see you should have that work re-done by somebody who actually knows how it's done and has ample experience. What you have there does not look right at all.

**Richard King** · 03-04-2021, 07:00 AM

How about showing us some photos of your tools and how your bluing them out. Hard to advise looking at those photos. As TC said it appears your scraping straight circular and not an X pattern, have maybe 2 % contact and you need 50%. Also as Orbital said. If you weren't shown how too you its hard as hell to scrape round bearings. Have you measured or miced the spindle in 8 places to be sure its round? Have you inside miced the bearings to see if they are round? How about any slop in size from one another? It's a guessing game with what you've told and shown us so far.

**gaminn** · 03-04-2021, 08:08 AM

To be honest, it wasn't me who did the scraping. It was a company that professionaly refurbishes machines in my country. I didn't want to mention that, intentionally, not to bias anyone. But obviously I biased everybody that it was me who did the scraping - I'm sorry for that.

The brand of the lathe is Czechoslovakian TOS SV 18 RA - the company refurbishes them very often.

So if you say the bearing needs 50% contact and I have maybe 2% then I think I have some argument they did their job not perfectly. They also ground the spindle itself (bearing surfaces, spindle's taper). I measured spindle's runout on its taper with spindle in these bearings, and I think it is pretty good (no runout visible with 0.01mm indicator).

**Orbital77** · 03-04-2021, 08:54 AM

Originally Posted by gaminn

To be honest, it wasn't me who did the scraping. It was a company that professionaly refurbishes machines in my country. I didn't want to mention that, intentionally, not to bias anyone. But obviously I biased everybody that it was me who did the scraping - I'm sorry for that.

The brand of the lathe is Czechoslovakia's TOS SV 18 RA - the company refurbishes them very often.

So if you say the bearing needs 50% contact and I have maybe 2% then I think I have some argument they did their job not perfectly. They also ground the spindle itself (bearing surfaces, spindle's taper). I measured spindle's runout on its taper with spindle in these bearings, and I think it is pretty good (no runout visible with 0.01mm indicator).

Watch this, it is a good intro to what it takes albeit with a couple of corners cut :

Scraping in a Myford MG12-M cylindrical grinder / part 7 (the end) - YouTube

You can do all this work yourself - it's not rocket science. Just practice on some scrap to get a feel for things and do NOT scrape where it isn't blue. It's very hard to put it back....