Priming oilite bushings with a vacuum chamber

[Canobi]

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.

[NortonDommi]

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?

[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

[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.

[Canobi]

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).

[Canobi]

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

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.

[Canobi]

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.

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....

[Frank S]

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

[olderdan]

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.

[neilabourjaily]

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.