Author Topic: Magneto Bearing removal  (Read 3063 times)

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Offline carcrank

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Magneto Bearing removal
« on: 16 Jan 2012 at 08:00 »
I have a Bosch magneto the bearings are shot, I am going to build the bearing extractor that I think Doug put up the drawing for. However the question is how do I remove the cup from the outside housing?
I thought that as the housing is brass maybe some heat?

I await your learned responses.



Offline Frank Lyn

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Re: Magneto Bearing removal
« Reply #1 on: 16 Jan 2012 at 15:19 »

There are two ways that I have done this.
1) Preferred method is using the proper tool.  There are bearing extractors just for this sort of job.  It consists of a (set of) three-segment, Expanding - External knife-edge collet and a slide hammer.  If you cannot get behind the cup with the knife edges, then there is usually a ridge or bump in the cup to grab hold of with the knife edges.   The Three-Bend-Finger extractors are too course for this application.   

There are similar extractors for the cone end.  They have knife edges on two semicircular plates that are bolted together.  Then a gear puller or press will get the cone off without fuss.

2) Un-Preferred method is to use a small cutoff wheel in a hand die grinder (Dremel Tool) to cut a diagonal slot in the cup and it will pop right out.

But this is just the beginning of your problems.  Bosch used insulating linen pieces on the cups to keep any current from passing through the bearings.  You can try to reuse these insulators if you are very careful or make new ones out of plastic or card.  Independent Ignition Supplies in the UK ( sell these in a variety of sizes.  No matter what you use, it is a trial to get just the right thickness and shape of the insulator to press solidly between the cup and brass piece without the cup acting as a punch to cut the insulator...... 

Do you have a Bosch DA1, 180 - 2, CW   by any chance?