Author Topic: how to press fit brass bearing sleeve into bakelite?  (Read 4888 times)

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Offline coppercone2Topic starter

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how to press fit brass bearing sleeve into bakelite?
« on: October 15, 2023, 02:18:05 am »
I took apart a roller inductor for service. there is osme nasty gears

one structure I had to take out is a brass bearing sleeve that was sitted in bakelite.

how do they do this? was this press fit? maybe I should try using freezing to put it back?

is there standard methods for bakelite press fit stuff? Otherwise I need epoxy or super glue. IDK how they got that sucker in there so tight. no residue for glue. Id prefer not to glue it if there is a technique.
 

Online Ian.M

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Re: how to press fit brass bearing sleeve into bakelite?
« Reply #1 on: October 15, 2023, 02:49:20 am »
It may have been moulded in. i.e. placed when the Bakelite precursor material was soft or liquid, then locked in place by the curing process.

If it was an interference fit, you've almost certainly enlarged the hole a smidgen by pressing it out, so short of re-making the bushing oversize, pressing it back in without adhesive bonding may fail.

One major concern with Bakelite (especially aged) is its tensile strength, and tendency to fracture.  I've press fitted bushings in Tufnol with good results, but that's fibre reinforced phenolic composite, so is far more fracture resistant.
« Last Edit: October 15, 2023, 03:02:44 am by Ian.M »
 

Offline David Hess

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Re: how to press fit brass bearing sleeve into bakelite?
« Reply #2 on: October 15, 2023, 03:08:35 am »
Bakelite will crack before it deforms, so inserts have to be molded in.  When you do the repair, the insert will have to be epoxied into place which works great with Bakelite.
 

Offline coppercone2Topic starter

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Re: how to press fit brass bearing sleeve into bakelite?
« Reply #3 on: October 15, 2023, 03:29:59 am »
hmm maybe its not bakelite IDK what to call it, its about 1/4 inch thick and it looks like wood but it cracks off corners if you drop it (has a cracked corner I need to repair).



Should I use epoxy or super glue?

I had to use a bearing puller and then bang on it with a socket (not on the bearing part) a few times when it was almost out because it was mega stuck.


The gears are all black and they have like black tary residue, really needs to be cleaned.

some gears are made of bakelite or whatever it is too. It kind of looks like card board gearing. but that is after a spring clutch brake thing

My plan is to clean/polish everything, resilver plate the spring thing with kool amp, clean the drum, replace the damaged dsub 15 connector and make a dsub 15 cable to test it with.
« Last Edit: October 15, 2023, 03:33:59 am by coppercone2 »
 

Online Kleinstein

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Re: how to press fit brass bearing sleeve into bakelite?
« Reply #4 on: October 15, 2023, 09:48:12 am »
If it is a tight fit super glue may hold it in place, but possibly to fast on mounting. Epoxy gives more time and can also fill a larger gap, while super glue is not suitable for a larger gap.

Bakelite and press fit is usually not such a good idea as bakelite is a bit brittle, especially if older and there is essentially no new baklite around.
 

Offline jpanhalt

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Re: how to press fit brass bearing sleeve into bakelite?
« Reply #5 on: October 17, 2023, 07:28:11 pm »
I would consider a Loctite anaerobic bearing adhesive.  Then you will not be rushed to get it seated.  If using ordinary superglue, I would use a slower setting medium viscosity.
 

Offline coppercone2Topic starter

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Re: how to press fit brass bearing sleeve into bakelite?
« Reply #6 on: October 17, 2023, 11:35:57 pm »
well I got another inductor coming because the last one had an accident. I will see how this one does. I have a feeling the one this thread was about was some how fucked up because literally everything was seized.
 

Offline TimFox

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Re: how to press fit brass bearing sleeve into bakelite?
« Reply #7 on: October 18, 2023, 12:11:15 am »
BakeliteTM phenolic is now rare, but you have an old unit.
It is very brittle.
Can your device be a more modern "linen-base" or "canvas-base" composite?
https://laminatedplastics.com/linenphenolic.pdf
These are more reasonable for drilling and machining.
 

Offline coppercone2Topic starter

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Re: how to press fit brass bearing sleeve into bakelite?
« Reply #8 on: October 18, 2023, 12:19:14 am »
its like from the 50's
 

Offline TimFox

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Re: how to press fit brass bearing sleeve into bakelite?
« Reply #9 on: October 18, 2023, 12:24:03 am »
Is the surface shiny?
I believe that real BakeliteTM is a phenolic resin (hence the need to mold it around the part).
The phenolic composites are paper or fabric filled with resin, where the fibers strengthen the result.
G-10 is a similar composite with epoxy and fiber glass.
« Last Edit: October 18, 2023, 12:29:27 am by TimFox »
 

Offline coppercone2Topic starter

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Re: how to press fit brass bearing sleeve into bakelite?
« Reply #10 on: November 07, 2023, 10:10:21 pm »
yeah IDK the old one that was all seized up is gone now but it looked like shiny pine wood. the new one thats nicer looks more like mahogany that is french polished.

I had to drill it to add standoffs for a dsub connector. when I drilled through it, the outlet of the hole was not super crisp, it reminded me a little bit of how OSB drills on the lip of the hole. Not as stiff as a PCB I guess. PCB kind of have 'chipped' holes, rather then partially attached crumbles on soft stuff. I assume that is a sign of cloth or some kind of puffy fiber, not glass fiber.

I am guessing that wood fiber insulation 1950's stuff (tar bags) mixed with some kind of resin. BTW that is apparantly as bad or worse then fiberglass even though its natural material. On the other hand, as far as my old research went, rock wool, which is a synthetic byproduct (slag) based, is not nearly as bad.

Kind of wonder how rock-wool PCB would do. Safer to drill?
« Last Edit: November 07, 2023, 10:14:58 pm by coppercone2 »
 


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