inside lapping a bearing bronze bushing

dian · Mar 7, 2020

what do you use as a lap? is annealed copper o.k.? and what compound? will diamond imbed?

edit: a bushing out of bearing-bronze sliding on a shaft, where i want to controll the fit.

thermite · Mar 7, 2020

dian said:
what do you use as a lap? is annealed copper o.k.? and what compound? will diamond imbed?

Bronze, I'm actually used to scraping, not lapping. The lube does the rest.

I'd seen Herr Pelz make a new Bronze bearing for an ancient B&S SG and have his wedge-shape German DI hold under half of its fifty-millionths division. No lapping required.

Bronze is also ameneble to "working". As-in stretching the bore, or hammering over a mandrel, clean-up pass on the OD.

But have a read, our own late and lamented "Texas Turnado" and his last-ever project. The rebuild of a Graziano TS, "Right here, on PM", even.

He teased through a shop-fab lap design and application that ultimately worked a treat:

Is it possible to hone the bore of a tailstock accurately enough in a home shop?

As importantly, there was a ton of discussion wrapped into the thread as covers it all really well.

Do keep in mind that bearing Bronze and CI are not the same goods? As-in mayhap the LAP should be CI?

Limy Sami · Mar 8, 2020

dian said:
what do you use as a lap? is annealed copper o.k.? and what compound? will diamond imbed?

IMO - Not a good idea, can you press a ball bearing or ball swage etc etc through to bring it to size

janvanruth · Mar 8, 2020

thermite said:
Bronze, I'm actually used to scraping, not lapping. The lube does the rest.

I'd seen Herr Pelz make a new Bronze bearing for an ancient B&S SG and have his wedge-shape German DI hold under half of its fifty-millionths division. No lapping required.

Bronze is also ameneble to "working". As-in stretching the bore, or hammering over a mandrel, clean-up pass on the OD.

But have a read, our own late and lamented "Texas Turnado" and his last-ever project. The rebuild of a Graziano TS, "Right here, on PM", even.

He teased through a shop-fab lap design and application that ultimately worked a treat:

Is it possible to hone the bore of a tailstock accurately enough in a home shop?

As importantly, there was a ton of discussion wrapped into the thread as covers it all really well.

Do keep in mind that bearing Bronze and CI are not the same goods? As-in mayhap the LAP should be CI?

i didn't know there were 0.1 Mu indicators,they must be very rare.

janvanruth · Mar 8, 2020

dian said:
what do you use as a lap? is annealed copper o.k.? and what compound? will diamond imbed?

edit: a bushing out of bearing-bronze sliding on a shaft, where i want to controll the fit.

if you want to really control the fit make it a bushing with a conical outside and a slit and a way to adjust fit by pressing it more or less into the housing.
the way head stock bearings were made.
,

thermite · Mar 8, 2020

janvanruth said:
i didn't know there were 0.1 Mu indicators,they must be very rare.

Haven't a klew what system yer in over there given y'all are so hard-headed yah don't even accept the conventional definition of above or below sea-level indicating drowning or simply bicycling to work.

Inches here. Where the money is. Wonder if there is a message in that?

SAG 180 · Mar 8, 2020

I ran some experiments with an aluminium lap in a bronze bush, even after thorough cleaning, the abrasive embeds in the bronze and will scratch up some clean, fresh aluminium surface.

crossthread · Mar 8, 2020

I would not use anything abrasive in a bronze bushing. It is too easy to leave abrasive material embedded in the bushing. You didn't say, but if this is oilite bronze then you should consider that what you do may "smear" the bronze and affect the porosity of the sintered bronze. I have had the best luck using an adjustable hand reamer to make bearings for things like tool post grinders and things of that nature.

dian · Mar 8, 2020

its what we call "rg7" (CuSn7ZnPb) with a hardness around 70 hb. im looking at sizes of 30, 40 and 50 mm, so an adjustable reamer would be nice, but i wouldnt know where to get one that big and im sure i couldnt aford it. splitting it is an option (and adding a housing with a differential screw) but im trying to keep it simple.

crossthread · Mar 8, 2020

Well if you want to keep it simple then I would get it as close as possible in your lathe. Then I would get a three stone brake cylinder hone and stone it by hand. The spring loaded stones will give you fairly equal pressure and I think you would have less of a chance of having abrasive slurry embedded in your bronze. You can get replaceable stones in various grades and the whole setup is very cheap (under $10). Use cutting oil and proceed slowly. I have mounted one of these in a tale stock chuck and used it to hone at very low spindle speed, but I think you can get it dead nuts on by just twirling it in your fingers. It will work on a taper as well.

johnoder · Mar 8, 2020

Boston - but then this is the sintered stuff

Mechanola · Mar 8, 2020

+1 for pushing through a steel ball. Takes a press, a ball, and oil. Quick and exact, no chips

dian · Mar 8, 2020

how much is a 50 mm bearing ball (i need a few bushings in several sizes)? and how do i adjust the fit?

richard newman · Mar 8, 2020

+2 for pressing a steel bearing ball thru. I did this once long ago, heated the ball in oil by 10 degree increments until the shaft just slid in. Very satisfying!

edit - just saw your post, I think there was some spring back, so an on size ball will burnish undersize.

thermite · Mar 8, 2020

dian said:
its what we call "rg7" (CuSn7ZnPb) with a hardness around 70 hb. im looking at sizes of 30, 40 and 50 mm, so an adjustable reamer would be nice, but i wouldnt know where to get one that big and im sure i couldnt aford it. splitting it is an option (and adding a housing with a differential screw) but im trying to keep it simple.

Given that the stuff turns - or bores - about as nicely as any material yah could ask for - I'm having a hard time trying to understand why you think you NEED to lap it.. but could use an adjustable reamer instead?

What's wrong with turning & boring it to your best efforts, then seeing to a goodly lube flush and "running it in" under power on the polished shaft it is meant to marry?

Or a substitute shaft. That's a burnishing process more than an abrasive lapping one, but Bronze is comfortable with that.

We even take advantage of it to make enduring-good bearings... out of Bronze.

Go figure.

dian · Mar 8, 2020

how much do you think can be "burnished" out that way? shafts are hardened and ground to h6. if i can increase the radius by 2 micron that should do it. on second thought, the bushing will warm up, so it wouldnt be so easy after all.

(in the end the bushing/collar will not have to rotate.)

jmkasunich · Mar 8, 2020

janvanruth said:
i didn't know there were 0.1 Mu indicators,they must be very rare.

C.E.Johansson Mikrokators are available in 0.1 micron (and 10 micro-inch if those are your preferred units).
Not cheap but readily available. Today's ebay listings:
C.E. Johansson Mikrokator - metric - mdl. 510-8 - .0001mm per division - FT17 | eBay
C.E.Johansson 510 E-4 Mikrokator .000010" Dial Indicator & Stand Calibrated 2019 | eBay

There are also soviet era russian clones out there for less money.
I've got a 1 micron and a 0.1 micron, paid less than $100 each on ebay.
Best I see right now for 0.1 micron is $150.
Mikrokator (+-0.004 mm) - metric 0.0001mm per division. USSR NEW! | eBay

John

Limy Sami · Mar 8, 2020

dian said:
how much is a 50 mm bearing ball (i need a few bushings in several sizes)? and how do i adjust the fit?

If you haven't got a ball, turn a shaft with a ''rounded bump'' in it the dia you want,rounding over with a file :eek:

………... it doesn't have to be hardened if it's only a few, just make sure said bump is nice and smoothly finished.

Then as above heat the bar a bit if you need a bit more.

dian · Mar 8, 2020

nice to know. i wonder how you adjust the height on this: C.E.Johansson 510 E-4 Mikrokator .000010" Dial Indicator & Stand Calibrated 2019 | eBay

black thumbscrew? it seems to be pinching a collar.

(you might be in the wrong thread.)

jmkasunich · Mar 8, 2020

dian said:
nice to know. i wonder how you adjust the height on this: C.E.Johansson 510 E-4 Mikrokator .000010" Dial Indicator & Stand Calibrated 2019 | eBay

black thumbscrew? it seems to be pinching a collar.

(you might be in the wrong thread.)

Rough position indicator, then fine adjust with screw under the stage that holds the part.

(you're right, this is the wrong thread for discussing mikrokators, this will be my last post on the topic)

inside lapping a bearing bronze bushing

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