TOS BPH-20 NA grinder- Worth restoring, and if so how to approach it?

[learning80]

I'm looking at acquiring a TOS BPH20-NA surface grinder, that has a bit of wear, to use in the short term and in the long term rescrape or regrind to bring back to very accurate levels. Is this a good idea?

These videos, of the same model, shows the way configuration -

My question is how do I tackle the ways, which look to be inserts, and are most likely hardened. I am guessing they were ground in place on the machine (though I'm hoping this is not the case) and thus you cannot remove them, regrind them, and then reattach them. If you could life would be a lot easier, I could just do this and take them all to a machine shop.

For the table could you put it upside down on a surface plate and check / scrape the ways when it is on there? I did this with another table and it worked well, so long as the scraping wasn't too heavy, but the item being scraped is, and it doesn't move around much. However I have no scraped in ways designed for cylindrical rollers. Or perhaps I should take it to a machine shop, though at a 1800mm table, I'm not even sure there are many or any shops in my area capable of regrinding it along its length.

Thanks for any assistance / advice.

 

[Richard King]

Brown & Sharpe Grinders used rollers like that on soft pocket iron ways and I took one of my 24" camelback straight edges and milled it narrower so it would fit in the pockets and scraped the ways. Holding a narrow scraper vertically and pull scraping worked the best.

Then I blued up the roller bearings and ran them in the pockets and put the table on the rollers and match fit the table to where they rubbed on the table pockets. Before doing this I would assemble the table and grind the table top even though the machine is worn as the table has a lot of stress in it and it will warp after grinding the table top. If you wait until you scraped it it will warp. So grind it, scrape it and regrind the tabletop with coolant (both times) .

If they are hardened you may try to grind the ways or lap them with a narrow straight-edge with diamond lapping compound. I have never done that on hardened ways, just saying that.

 

[Richard King]

I see your down under. You can contact my Mate who used to belong to this forum. He is a machine rebuilder and used to host scraping classes inside his plant. He also has a way grinder as does another former member RC99. Give him my regards.

Phillip Fehring
P & L Machine Tools Pty. Ltd.
24 Bostock Court
Thomastown Victoria 3074
Australia
Tel: +613 9466 3655
Mob: 0412 555 326
[[email protected]][email protected]

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[learning80]

Thanks for the advice Richard.

My main concern now is the x-axis. For this the ways are 1800mm long, approximately, along their longest length. The ways where the cylinders ride are approximately 10 to 15mm wide (at a guess).

I don't have access to the machinery needed to make a straight edge of this length and this width. I do have access to an 1800mm long straight edge of regular width but it obviously can't spot within the groove. I gave up on the machine for this reason. I have some experience scraping, having scraped in a small milling machine, but always I've used straight edges longer than the ways I've been scraping. When I've tried to use a smaller straight edge I've found I can introduce error very quickly. I suppose there must be a way to avoid this, perhaps some technique using a level along the surface you are scraping, to decide which parts to leave and which parts to hit? Anyway, I abandoned it.

Then it occurred to me, and this might be completely mad - could I build up the groove where the ways are with small individual pieces of ground cast iron, screwed to the table? Small enough so as not to induce a major bow on the table (or screwed to individually scraped areas)? And then scrape the 1800mm long section of these raised pieces with the straight edge I can borrow - and then attach linear rails to it? It seems slightly mad, and some of the surface grinder brackets would need to be remade/lengthened, but aside from the small pieces introducing a bow, I would think it might work.

 

[10 fingers]

In another lifetime, I was a field service engineer for Reid surface grinders. Would occasionally evaluate a machine for extensive repair. Before going too far down the rabbit hole, inspect spindle nose TIR. Max allowance is somewhat subjective depending upon application. My experience is with Pope and Whitnon product. If over .0002 TIR is about useless for accurate work. Spindle rebuilds are very expensive. Hardened, way strips are easily damaged. Rollers will Brinell strips if any table impact. Can be tough to inspect for. Only discovered when doing fine grinding. Bottom line, hand feed surface grinders can last a lifetime or be destroyed in instant. Once damaged, are disposable. New Mitsui grinders are a tremendous value.

 

[learning80]

In another lifetime, I was a field service engineer for Reid surface grinders. Would occasionally evaluate a machine for extensive repair. Before going too far down the rabbit hole, inspect spindle nose TIR. Max allowance is somewhat subjective depending upon application. My experience is with Pope and Whitnon product. If over .0002 TIR is about useless for accurate work. Spindle rebuilds are very expensive. Hardened, way strips are easily damaged. Rollers will Brinell strips if any table impact. Can be tough to inspect for. Only discovered when doing fine grinding. Bottom line, hand feed surface grinders can last a lifetime or be destroyed in instant. Once damaged, are disposable. New Mitsui grinders are a tremendous value.

I can't inspect the grinder again, but during the short test demo I got, it produced what I thought was a good finish across a few blocks. It seemed to grind well. I didn't have an indicator on hand to check the spindle, so I'll just have to chance it. It took a few heavy cuts and 'sparked out' well. I'm new to grinding incidentally.

 

[michiganbuck]

We had replaceable ball ways sent to a grinding shop for regrind. The Cincinnati company said that we could grind up .to .035" from the V and flat t ways.
with grinding and new balls and shimming back to height, we restored to new specifications.

 

[michiganbuck]

Qt: (If over .0002 TIR is about useless for accurate work...)
But wheels are dressed to be running very close and a .0002 tir can be Ok for most shop's requirements
A .wiggle in a warmed up spindle indicates new bearing may need be replace,

 

[MCritchley]

In another lifetime, I was a field service engineer for Reid surface grinders. Would occasionally evaluate a machine for extensive repair. Before going too far down the rabbit hole, inspect spindle nose TIR. Max allowance is somewhat subjective depending upon application. My experience is with Pope and Whitnon product. If over .0002 TIR is about useless for accurate work. Spindle rebuilds are very expensive. Hardened, way strips are easily damaged. Rollers will Brinell strips if any table impact. Can be tough to inspect for. Only discovered when doing fine grinding. Bottom line, hand feed surface grinders can last a lifetime or be destroyed in instant. Once damaged, are disposable. New Mitsui grinders are a tremendous value.

Valuable info in that post, surprised the runout value is that large.

Used ball way grinders make me nervous, I’ve passed on a few with brinneled ways.

 

[10 fingers]

Valuable info in that post, surprised the runout value is that large.

Used ball way grinders make me nervous, I’ve passed on a few with brinneled ways.

I agree with you, .0002 TIR would not be acceptable for any grinder I'd consider purchasing. In field service, no attempt was ever made to service spindles. They were returned to the manufacturer. Assume upon replacement of bearings, the nose taper was precisely ground as an assembly. At new machine build, a .00005 test indicator was motionless. Shame American, surface grinder manufacturers were too stupid to compete. In 1984 Reid was still using thread milled crossfeed and elevation Acme screws. Japanese grinders had silky smooth screws done by thread grinding. Ball ways were almost frictionless. Any debris entering the ball ways was pushed aside. Roller ways would climb over it. Of course, a ball way machine must be disassembled to move and work placed on the chuck gently..

 

[learning80]

The spindle incidentally is a plain bearing spindle. I'm hoping then that as the surface finish is adequate and it has adjustment it is ok.