Priming oilite bushings with a vacuum chamber

I built this chamber a few years ago to degass resins for verious replica prop projects. It took a back seat as metals started to play a more crucial role in my chosen hobby, which has led to me to own a lathe, and more recently, a Dore Westbury Mk1 mill.

She's in need of a little TLC and one job is to replace the planetary pulley assembly bushings. I bought a set of oilite bushings but forgot to ask for primed, so it was on me to that job.

I didn't fancy heating the bushings up and risk them warping (even though they're supposedly stable in that area), so it was nice to finally have a reason to dig the vacuum chamber out again, we had some good times back in the day.

https://youtu.be/B9uDdoRlrD8

Nice one Canobi,
What else have you impregnated? I did some wood pieces for a friend who makes knives with a heat activated resin for use as scales. I use an old fridge pump what are you using?

I like the idea, there have been a few times when I have had to re machine the OD or ream the ID of oilite bushings. I have always tried to buy pre primed bushings which are individually sealed in plastic pouches however this is not always possible when having to buy in bulk. turning the OD will always leave minute particles embedded which I felt was not a problem as they would be pressed in anyway for cleaning the Reamed bores I have usually saturated a cloth with oil and used that to remove any particles which would dislodge. For non packaged or bulk bushings I would normally place them in a container filled with oil then boil them for a few minutes to insure they were well oiled, but your vacuum procedure looks to me as a much better way. For reaming a cleaning routine would still be necessary but at least you would know the bushing was oil filled

Hi Canobi
A note on sintered bushes, if it is important that it is truly concentric it is worth checking the bushes you have purchased before using. I recently was asked to reduce the o/d of a new bush for a BSA gearbox only to find it had a run-out of .006 tir on a true mandrel, fortunately for him the amount reduced took care of it, a check in a V block would do.
I am not sure of the quality of some sources these days and it would seem that punch/ die and core rod sets used to produce some of these are either poorly made or being used beyond their service life, any score marks are a warning sign.
We used to make tool sets for Manganese Bronze and their bushings were of good quality.
I have always understood that a 24 hour soaking in warm oil does the trick but a vacuum chamber is obviously better if you have one.
Nice work.

Thanks NortonDommi :)

The bushings were my first impregnation, the chamber was primarilyp used to degass liquid silicone rubbers and resins prior to casting,

The pump is a 240v 30cfm jobby, normally used for changing the gas in air conditioning units. I acquired it from eBay for cheap, but its a little undersized for my 12" x 12" chamber, I could do with a 60cfm unit to halve the time it takes to get to a decent negative pressure (resin degasses at around -25, silicone needs -28 or more).

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Originally Posted by Frank S

I like the idea, there have been a few times when I have had to re machine the OD or ream the ID of oilite bushings. I have always tried to buy pre primed bushings which are individually sealed in plastic pouches however this is not always possible when having to buy in bulk. turning the OD will always leave minute particles embedded which I felt was not a problem as they would be pressed in anyway for cleaning the Reamed bores I have usually saturated a cloth with oil and used that to remove any particles which would dislodge. For non packaged or bulk bushings I would normally place them in a container filled with oil then boil them for a few minutes to insure they were well oiled, but your vacuum procedure looks to me as a much better way. For reaming a cleaning routine would still be necessary but at least you would know the bushing was oil filled

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Funny you should mention sizing ODs and IDs, after installing the bushing in the vid, I discovered it won't even go on the shaft and it was easy slide fit before.

I'm with you on turning ODs and not worrying about particles but I really dislike the idea of ID turning. Instead, I think I'm going to make a drift and oversize one half in steps by about .003" each time. The bore is only shy by around .006" so the drift won't need to be very long.

Quote:

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Originally Posted by olderdan

Hi Canobi
A note on sintered bushes, if it is important that it is truly concentric it is worth checking the bushes you have purchased before using. I recently was asked to reduce the o/d of a new bush for a BSA gearbox only to find it had a run-out of .006 tir on a true mandrel, fortunately for him the amount reduced took care of it, a check in a V block would do.
I am not sure of the quality of some sources these days and it would seem that punch/ die and core rod sets used to produce some of these are either poorly made or being used beyond their service life, any score marks are a warning sign.
We used to make tool sets for Manganese Bronze and their bushings were of good quality.
I have always understood that a 24 hour soaking in warm oil does the trick but a vacuum chamber is obviously better if you have one.
Nice work.

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Thank you indeed good sir, and for the heads up, I had just assumed that bushings would be made true.

I think one of the pulley sections may be imbalanced, an off centre bushing could well amplify the imbalance if the circumstances were right. I don't have a wheel balancer so looking into making one. It'll probably be somewhat amateurish as I'm still pretty green but as long as it works....

Where it comes to sizing the bushings back in the day when I was rebuilding a lot of very old carburetors, magnetos, distributors and other things for a couple of local antique car clubs I often had to bore and ream out the various bodies to accept bushings then make the bushings since for most things either these components were not manufactured with them installed or no off the shelf replacements existed.
I had a rule of Frank which may or may not been according to Hoyal and almost certainly contrary to sections in the Machinist bible, but since I didn't own one at the time through experimentation I came up with for the OD the bushings in things which were only periodically rotational which did not spin such as the choke and throttle shafts I used the formula of .0001" oversize per .100" hole diameter meaning that a hole of .500 the bushing would be .5005 for 1" it would be 1.001
for rotating shafts with the bush fixed in the bore I used.0002 per .100" diameter
I made installing mandrels to be .0001" per.200" shaft diameter this worked well for me in the smaller less than 1" diameters. For larger bores especially for hardened steel sleeves I used the recommended Timkem bearing engineering press fit calculations the exception being those in the Aluminum transmissions I did which I flanged doubled the interference fit then linear knurled the OD's prior to hardening Since the process of hardening caused the bushings to shrink I adjusted my dimensions accordingly
I always found the use of mandrels for installations to be the up most importance for any bushing install for any type of material
Like I have said previously any machining skills that I have or think I have either real or imagined I learned completely on my own

Self taught or not Frank you have wealth of experience that most would envy, there are not that many guys left that have the skill or patience to bring a scrap item back to life. It is often easier to remake a part but much more satisfying to repair an original.
Your interference fits are pretty much what I have used.

Please, site host, make a place for Frank S's observations and solutions. I mean a site similar to tool maker sites. I agree with olderdan. Frank gets it. His solutions are elegant.

This is a good place to start: Homemade Tools built by Frank S - HomemadeTools.net

Hi
Great idea and having the clear top to see what is happening in the chamber is great to.
On machining oillite bushes, I worked for a science research lab and we never reamed the holes due to the reamer potentially closing the pours of the material. (This is what I was told).
Therefore, we always machined the bores with a HSS tool to a bore gauge. Not sure if this was just company policy or this is the correct way to machine oillite?
The Home Engineer

I ended up doing a fair bit of research and came to the conclusion that as long as the tool doing the cutting is fresh and sharp, it would reduce any smearing which would block the holes. I used a brand new reemer and indeed the vast majority of holes were visible afterward. Saying that, I don't intend to ream it next time as it's only shy by about a thou, so once it's been dropped into the pulley, I'll heat it up which should be enough to drop it on the shaft. Probably need a bit of elbow grease to loosen the pulley up after that but it'll negate any possible flaw I might introduce by messing with the bore on my old machines.

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Originally Posted by Canobi

I ended up doing a fair bit of research and came to the conclusion that as long as the tool doing the cutting is fresh and sharp, it would reduce any smearing which would block the holes. I used a brand new reemer and indeed the vast majority of holes were visible afterward. Saying that, I don't intend to ream it next time as it's only shy by about a thou, so once it's been dropped into the pulley, I'll heat it up which should be enough to drop it on the shaft. Probably need a bit of elbow grease to loosen the pulley up after that but it'll negate any possible flaw I might introduce by messing with the bore on my old machines.

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If it is undersized before being pressed in the pulley it will be more so afterwards.be sure to used a proper sized mandrel in the bushing to press it in the pulley this will negate any reduction of ID. Some say this may not be the best practice but I like to freeze the bushing and the mandrel for several hours before pressing in the pulley. then allow them to warm naturally before pressing the mandrel out of the bushing For me it seems to help the install to go smoother and compacts the bushing slightly instead to deforming it. the bush should turn freely on the shaft to prevent the possibility of seizing and spinning in the pulley.

The bushing was on size and moved freely but with no play prior to pressing it in the pulley. It was after pressing it in that I found the bore had become too small, which prompted the reeming.

I ran a very similar process to which you describe and I put the bushing in the freezer for a couple hrs, I hadn't considered turning the mandrel/press bar the same size as the shaft though, as you say, the bushing would have compressed to exact size when it warmed up, saving me an extra job and loss of precision. That's a little gem tip right there, I like it very much, thank you :)