Rebuilding Machine Soon- general question about journal clearances and brass inserts

Hi All-

I'll be rebuilding my 10L soon (working my way through painting currently). This is a total restoration, everything is being re-ground and scraped in, etc etc. I'd like to fix any cast iron bearing wear in places like the gearbox and apron.

Could some speak to what the ideal clearances are between journal and replacement bearing? I assume 0.001" would be sufficient for items like the gearbox axles and cross slide crank journal. Am I way off base?

Also- what's a good interference for the brass/cast-iron press fit? Do you guys press fit then final bore the brass to size after the press fit? Or do you precision machine the ID and OD for the brass on a lathe and use loctite 660 or equivalent for installation of the bearing into the cast iron?

Thanks for your advice, it's appreciated.

Bump! Is my question to cryptic? I'd be happy to explain better.

xplodee said:

Bump! Is my question to cryptic? I'd be happy to explain better.

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Maybe you have the "repainters" who like to think of themselves as "restorers" confused.

Also- what's a good interference for the brass/cast-iron press fit?

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Machinery's Manual has a section on plain bearings, fits, and applications. I believe that for slow speed shafts with oil lube, under 1" dia. that your proposed .001" clearance is good. Funny, but .002" can actually feel quite sloppy. So I try not to err in the large direction.

Do you guys press fit then final bore the brass to size after the press fit? Or do you precision machine the ID and OD for the brass on a lathe and use loctite 660 or equivalent for installation of the bearing into the cast iron?

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Prefer the first for fit, alignment and concentricity. Have done the second where the part was not already set up to machine. I try to remember to make the bushing first, with a correct, or repair target OD. Insert after boring seat before removing from machine by pushing in with a stub mandrel in the quill or the TS if done on a lathe. Then bore or ream in same setting.

There are circumstances where putting the bushing on the shaft and installing with loctite (being sure it does not seize the shaft is a fair alternative to line boring if it is a casting that you do not have the facilities to machine.

PS, I'm thinking actual bearing bronze, not oilite sleeves, which are (too?) easy to compress. Oilite has its uses, but is generally not a good replacement for machine plain bearings.

smt

Thank you, STM.

I was planning on 932 bearing bronze for the job. I agree, 0.002" can feel really nasty. Nothing beats the feel of a 0.0005+ clearance with some oil but I don't know if that's a big enough gap for proper oiling. Will read up on this. Thank you.

When you do the press fit as you've described above (with the cast iron still mounted on the mill), do you do your final bearing bore pass on the mill AFTER the press fit? I am worried that the press fit will shrink the ID of the bearing bronze below what I machined it to on the lathe.

thomasutley said:

Maybe you have the "repainters" who like to think of themselves as "restorers" confused.

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I'm not sure what you mean by that… He said "This is a total restoration, everything is being re-ground and scraped in, etc etc". That's a pretty complete resto, and he's currently asking about bearings.

Bernie

itsmeBernie said:

I'm not sure what you mean by that… He said "This is a total restoration, everything is being re-ground and scraped in, etc etc". That's a pretty complete resto, and he's currently asking about bearings.

Bernie

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It was ment as an insult to people that just repaint their lathes and do not tear it down and refit everything.
Not talking about the op.

swatkins said:

It was ment as an insult to people that just repaint their lathes and do not tear it down and refit everything.
Not talking about the op.

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Hah hah gotcha.. I tried rereading it and missed that hah hah
There are a few here who would be serious saying that hah

Bernie

Xplodee queried:

When you do the press fit as you've described above (with the cast iron still mounted on the mill), do you do your final bearing bore pass on the mill AFTER the press fit? I am worried that the press fit will shrink the ID of the bearing bronze below what I machined it to on the lathe.

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smt previously commented:

I try to remember to make the bushing first, with a correct, or repair target OD. Insert after boring seat before removing from machine by pushing in with a stub mandrel in the quill or the TS if done on a lathe. Then bore or ream in same setting.

Click to expand...

smt

ID reduction after a press fit is a serious concern for bearings. I've even seen ball bearings seize up after a press fit that's too tight.

In the case of busing bearings, you might consider that "line to line" is really a light press fit and if the loading on the bearing isn't too high, it may stay in place without needing the addition of modern chemicals. However, "line to line" requires a VERY accurate sizing of the housing bore and bearing OD and they both have to have a pretty good finish for this scheme to work. It might be worth a try if you have the patience to do the machining accurately.

Thank you, smt. Much appreciated.