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Old 02-22-2018, 10:03 PM
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Bob Galanter
 
Join Date: Sep 2005
Location: Whitefish Bay, Wi (Milwaukee)
Posts: 1,053
Bumble Bee Re-Stuffing cont:

5. In this step, we continue to remove the foil bundle with successively larger drill bits. Your drill bits need to be Factory Sharp. Dull drill bits will crack the fragile Bakelite. As with the 1/4" drill, advance and withdraw the bit and slowly work you way down to the opposite end, being careful not to break through the opposite end of the Bakelite body. I was able to drill as large as 29/64" which was able to accommodate a .2uf 630v yellow metalized polyester axial capacitor. All you have to do at this point is insert the new capacitor and use some 5 minute epoxy to re-attach the Bakelite end piece. Photos #7 thru #10

I would imagine your first thought is can this be done without a lathe? Perhaps on a drill press? It will never happen, take my word for it. If you try to drill the foil bundle out using a drill you are going to break the Bakelite when you start to enlarge the inside diameter to accommodate the diameter of the new cap. This is not just a mater of removing the old foil bundle, this involves machining the inside diameter of the Bakelite.

Shop time is about 20 minutes per capacitor once I developed the skill set and methodology so that the Bakelite did not break. If you were to hire a machinist to do this I would expect it would cost about $20 a pop.

These were large Bumble Bees. .2uf and .15uf 400 volt caps. I would imagine this would be possible with physically smaller Bakelite caps as well, just as long as your new cap is small enough to fit inside the old Bakelite body.
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