Press Fit Oilite bearings in 6061 now too small.

[RKW]

I'm working on a dial indicator holder for my lathe cross feed. It consists of four parts, a mount, an end piece, a movable/adjustable piece, and the rails. These are all from 6061 aluminum except for the rails, these are 1/4" drill rod.

I have pressed oilite bearings into the movable portion in the appropriate sized holes and the rails no longer fit. The bearings did once fit but now they are smaller.

Should these types of bearing be press fit like I did or should I have had a slip fit and used Loctite? I did have them to the correct size again by reaming and honing but then I needed to slit one side through the body and bearing for a hold-down clamp. Now that one has closed back up too tight to fit. Possibly internal stresses since this is not Mic 6 plate?

Just wanted to know what others thought as to the proper way to do this so I would not have this in the future. I like figuring things out on my own when possible, but I have had to put in more work in on something that I believe should be simpler.

[Paul in OKC]

Ream them out. I build a little widget that uses the same type bearing press fit into 6061 aluminum. I want the press fit, and just run a reamer thru before assembly.

[Mcgyver]

I

Just wanted to know what others thought as to the proper way to do this so I would not have this in the future. I like figuring things out on my own when possible, but I have had to put in more work in on something that I believe should be simpler.

oilite and such are expected to have the ID reduced when pressed in, they are made slightly oversize to be a light press into a hole reamed the nominal size. Machinery's handbook somewhere gives the calcs based on what OD and hole size will produce what ID

ideally you shouldn't ream them, smears the surface and takes away the advantage of them be self lubricating. whether it matters or not will be depend on how hard working and critical the application is.

mostly, if pressed in a reamed hole, the ID will close up to be about right for a running fit on the shaft. when this doesn't work, its handy to be buy them a little long and one OD larger than need, hold them in a collet and turn to whatever you need it to be before press fitting.

[kf2qd]

Back when I used to do a bunch of oilite bushings we had a set of sizing balls (really just ball bearings, 0.00, +0.001, +0.002) that we used to bring the ID to finished size. Would just push them through the bushing and it would cold form the bore. (worked real nice on mild steel to give a nice smooth hole, just added a little oil to keep it from galling)

In soft metals like brass and aluminum it makes a nice way to come up with a s-m-o-o-t-h bore really quick.

[Black_Moons]

Awsome ball bearing trick, know anywhere to buy these sets? or do you just buy a 100 bag of cheap chinese ball bearings and bust out the micrometer to find a few oversize ones?

[RKW]

McMaster seems to sell precision ground ball bearings. I'll have to try a few test holes with this sort of thing just to see. I probably should have done the same with the oilite bearing before finding out this particular problem on the final piece. But hey, as long as I'm learning, I'll do it over if necessary but I don't think I'll have to.


Awsome ball bearing trick, know anywhere to buy these sets? or do you just buy a 100 bag of cheap chinese ball bearings and bust out the micrometer to find a few oversize ones?

[rkepler]

I'd be careful about pressing out the inside diameter of an Oilite bearing. If there's a significant change in diameter the ball may have pressed closed many of the passages needed for oil to migrate in to the shaft from the rest of the material. The same can occur when machining with dull cutting tools, they can smear the bronze with the same effect. I'd ream back to size with a fresh sharp reamer.

[RKW]

oilite and such are expected to have the ID reduced when pressed in, they are made slightly oversize to be a light press into a hole reamed the nominal size. Machinery's handbook somewhere gives the calcs based on what OD and hole size will produce what ID

I have not found anything so far on this but will keep looking.


ideally you shouldn't ream them, smears the surface and takes away the advantage of them be self lubricating. whether it matters or not will be depend on how hard working and critical the application is.

Makes complete sense that this would happen. Glad it is not a high speed/duty operation.


mostly, if pressed in a reamed hole, the ID will close up to be about right for a running fit on the shaft. when this doesn't work, its handy to be buy them a little long and one OD larger than need, hold them in a collet and turn to whatever you need it to be before press fitting.

Wouldn't this still cause the same smeared surface but only on the outside now? Or would that only be cause by a reamer rather than a sharp cutting tool?

[S_J_H]

I'm working on a dial indicator holder for my lathe cross feed. It consists of four parts, a mount, an end piece, a movable/adjustable piece, and the rails. These are all from 6061 aluminum except for the rails, these are 1/4" drill rod.

Sounds interesting. Is it anything like what I built for my SB9A ?
http://i109.photobucket.com/albums/n48/S_J_H/SOUTHBEND%209/crossslideDI001.jpg

Steve

[Mcgyver]

I
Wouldn't this still cause the same smeared surface but only on the outside now? Or would that only be cause by a reamer rather than a sharp cutting tool?

Russ makes a good point on reaming the ID, that if the reamer is very sharp it might be ok....but very sharp means very sharp....you know how a file kind of sucks on brass after its been used on steel? i'd be thinking that kind of sharp.

To your point,. it may well smear the OD, but do we care? its in the ID where the bearing surface is and where we want the lubricant to be able to flow

[macona]

Oillite bushes are intended to be reamed out after press fit.

[Braindead]

I'm working on a dial indicator holder for my lathe cross feed.

Would you mind posting the details of your design? I've been considering making one myself.

TIA

[John Stevenson]

Technically they have to be bored.

This is the spec sheet from the people who now own oilite.

http://www.bowman.co.uk/Resources/Machining%20LO.pdf

.

[oldtiffie]

Or alternatively:
http://www.beemerprecision.com/PDFs/castBronze_designData.pdf

[Mark McGrath]

Oillite bushes are intended to be reamed out after press fit.

Rubbish!
They are supposed to be single pointed.Reaming closes the pores and they are no longer self lubricating.

[Mcgyver]

Oillite bushes are intended to be reamed out after press fit.

where did you get that from?

[wierdscience]

They are intended for a lite press fit with no reaming.A nominal .500 x .375 bushing will be .502 x .376 in reality,once pressed in place the bore will measure .375-.3752.Unless they get distorted during the press operation.

You could press them back out and increase the hole size slightly,or push a ball bearing through them or just ram a lefthand spiral right hand cut reamer through the hole and be done with it.

Most likely the holes are actually egg shaped and only need rounding,in any case your only going to be removing a few tenths and it doesn't make much difference how you do it.

[oldtiffie]

Last item - last page:
http://www.beemerprecision.com/PDFs/castBronze_designData.pdf

Now - combining that with John Stevenson's post at:
http://www.bowman.co.uk/Resources/Machining%20LO.pdf

So- you can turn and/or bore or ream - suit yourself.

I am assuming that the people that posted those links know what they are on about.

[SDL]

Last item - last page:
http://www.beemerprecision.com/PDFs/castBronze_designData.pdf

Now - combining that with John Stevenson's post at:
http://www.bowman.co.uk/Resources/Machining%20LO.pdf

So- you can turn and/or bore or ream - suit yourself.

I am assuming that the people that posted those links know what they are on about.

John is talking about the sintered porous bushes that we know as oilite in the UK the Beemer page is for cast broze but has a reference to porous on page ??? at the top.

Steve Larner

[RKW]

Actually, yes! I had forgotten where I saw it but it must have been yours. Very nice design and looks great. I just ended up drawing it scaled to what I need it for.

What was your installation procedure of the sleeve bearings? To ream or not to ream ... we have seen both here. And although I thought I understood why, anyone who followed one of the links provide will see that the manufacturer states, "Reaming the bearing for finish sizing is the usual method employed."


Sounds interesting. Is it anything like what I built for my SB9A ?
http://i109.photobucket.com/albums/n48/S_J_H/SOUTHBEND%209/crossslideDI001.jpg

Steve

[SDL]

What was your installation procedure of the sleeve bearings? To ream or not to ream ... we have seen both here. And although I thought I understood why, anyone who followed one of the links provide will see that the manufacturer states, "Reaming the bearing for finish sizing is the usual method employed."

No that's for cast not porous unless you have see page ????

Steve Larner

[Rich Carlstedt]

I think we are getting off point here.
Oilite bearings are purposly made oversize.
The press fit determines the final size.
It doesn't matter what it is, as it varies a bit based on diameter.
if as another poster said, the OD is +008 and the ID is +.002 ( I have seen .005 !), and you want a running .001 diametral clearance, you make the OD a .001 press fit (it will hold!) to reduce the bores .002 to .001

Ok, say you are rebuilding a machine and the OD bores are done by the manufacture
NOW if you find that the OD's bore is smaller than you want.
You turn the OD (!) of the oilite to give you the fit you need.
In 40 years of machine building, we never reamed the ID of an oilite.
You might as well throw it away, as it will wear very fast, until the passages are uncovered.
Machining the OD is tremendously more simple and fast ( use a taper mandrel)
Boring, drilling, and reaming make the product less effective and are slower.

Rich

PS Solid Bronze bearings are a whole "nuther" issue.
Then you can ream, but you also cut grease/oil grooves/patterns for lubrication.

[darryl]

I've had a few experiences of my own with oilite bushings. What it came down to for me was to make the fit a light press and don't do anything to the ID. It doesn't take much force to crush them down too small, so maybe it's time to make sure you can accurately measure what you're boring to press the bushing into. Make yourself a few test plugs. Turn one to be 2 thou smaller od than your bushing, another one 1 thou smaller. As you bore for the bushing, the 2 thou one should be able to slip in easily, which is the point where you can take spring passes to reach the point where the 1 thou one can barely be pushed in by hand. Use some light oil on the test plugs to help prevent jamming them. If the 1 thou small plug is a snug fit, that should be about right to press the bushing in and have it not become too small on the ID. You should of course check the ID of the bushing to see what you're actually dealing with. You may need to crunch it down more if the ID is that much too large for your shaft.

The worst thing for me is getting impatient right at the end, where the tendency is to bore out too much and wreck the job. Er, no wait- I've never done that :)

Once you have the bore sized as above, measure with whatever instrument you use, then put two and two together. For instance, your reading might show the bore to be a little small, when you know what size it actually is by the fit of the test plug.

Take care when making and using the test plugs- make sure the pieces are at room temp before taking the final cuts to make them the exact size you want, and make sure the workpiece has cooled before you use the test plugs.

A little experimenting with boring, measuring, and fitting went a long way with me towards being able to make proper press fits.

[2tenths]

I can see that only the tough survive on this forum. If measuring bore size is part of the issue here, I always liked the 2 gage pin method with over / under gage pins.

[Evan]

What difference does it make if the bushings are bored, reamed or turned or even swaged? In this application I would use either cast iron bushes or solid bronze. It's not like the immense friction from the blindingly fast motion of a cross slide will melt them to the shaft or something. :rolleyes:

[darryl]

I was wondering when someone would point out that fact. I don't think I've ever seen a blindingly fast crosslide, but there's a first time for everything :). Way lube on brass or bronze bushings would be fine I'm sure for this project that RKW is making. Any of the stated ways of resizing the bushings is going to be ok as well.

Now immense friction is something that I know about. I carry some of that around in my head everywhere I go. It's used in the pathways between my memory sticks and my brain. Getting older I guess.

[dneufell]

S J H ....nice....very nice................Dean

[S_J_H]

Thank you, I find it a very useful device that was worth my time to make.
On mine, the ground shafts were taken from a printer. I reused one of the sleeves that came from the same printer. I machined up the other (split) sleeve from 660 bronze. I used loctite to retain them. I'm a big fan of loctite. It depends on the application but in many cases leaving the bushing to housing fit a bit on the loose side and using loctite, you can get excellent alignment.
Steve

[Don_Hartman]

Hello

I generally make a arbor or a shouldered bar that has the same size OD as I want the ID of the bearing to finish at. That could be anywere from .0000 or more depending on the fit you want. I do take extra care with the finish and the size when making this arbor. When this is used in pressing in the new bearing it keeps the ID round and helps to sizes it for your shaft. I most recently done this on a shaper I rebuilt and had great success in the past with this. I do also smear a little heavy weight oil or grease on the arbor.

When possible I will thread the arbor and make one for the other bearing bore , that one with a through hole for threaded rod. This keeps the bearing in alignment as it is pulled into the bore. I also try to avoid hammering in a bronze bearing at all cost if possible.

Don

[DICKEYBIRD]

Just for the halibut, I think I'll turn the O.D. on one, ream the I.D. then pump it full of oil & squeeze the heck out of it between 2 fingers. If she sweats oil easily, no problemo wid the turnin' or the reamin'. :)

I used to get a kick out of doin' the oily-squeezy thing putting in crankshaft pilot bushings back in my yute.

[Rich Carlstedt]

Steve, you are correct.
You can get beautiful bearings and allignments by using loctite as in your comments.
This is how high speed spindles are done on some machines.
The bearing are placed on a shaft and inserted in the bearing bores and loctited in place .
For high speed (grinding ie.) you want no mis-allignment or drag.
and it doesn't get any better than that

Rich

[RKW]

Thanks for all of the info and many replies, although as usual there were a few contradictory posts. Everyone here seems to find what works for them and that is all that matters.

I was not aware that sintered sleeve bearings where expected/designed to change ID once press fit. I do like the idea of a properly sized, shouldered, and greased mandrel, and may try it at some point. Especially if I cannot get the current bearings to work or size properly.

One thing that was not commented on was the slit side bearing closing down after it was sized. Was it like I had thought, internal stresses and a pretty typical thing to expect?