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I'm having some problems with re-assembling the upper works on my Columbia BET cylinder phonograph. The mandrel gear and pulley are held on the mandrel shaft by a reverse threaded nut that just exerts pressure, forcing the gear and pulley tightly against a “step” in the mandrel shaft. Here's the problem, when the mandrel is put in position in the casting, the “step” should just slightly protrude from the inner milled face of the casting, where the gear sits. Otherwise, when the nut is tightened, it forces the gear against the casting, and it won't turn. Problem is, on this one, when the mandrel is in position, the step is a hair's thickness inside the casting. When the nut is tightened, it just makes the whole assembly bind.

I've taken this apart and reassembled it tens of times and just can't think of anything that could be causing this. Any ideas? I've included pictures of the mandrel and shaft, and the assembly, outside of the casting. The same system is used in the BF, and I believe in the BG.

Benjamin

Where are the pictures?

Sorry, forgot to add them I've added them to my first post.

I am trying to remember how I worked on my BF...

Did you put a washer between the gear and the casting?

Bill

Yes, there's a washer there. It's about the same diameter as the gear.

Here's some pictures to show the problem. I'm comparing the BE to my BF, which works as it should.

Here's a picture of the BF; as you can see, the "step" in the mandrel shaft is proud of the casting, so the gear is pressed against the shaft's "step". Here's the problem with the BE; as you can see, the step is slightly under the surface of the casting, so the gear is pressed agains the casting, instead of tightened onto the shaft.

Benjamin

Try two washers...

Hi Curt,
Not really understanding how that would help; the washers would then be forced against the casting by the pulley nut.

Hey Ben,

Just an observation, but it sure looks to me as if there is quite a buildup of hardened grease/oil on the surfaces. I would clean the mating surfaces and all related parts to remove ALL debris.

I dunno, maybe it's just the pictures...

Best,
Fran

Hi Fran,
That's just soft stuff there; I did clean it though right down to bare metal, but the "step" is still a hair below the surface of the casting. I can't find any debris that could be causing the mandrel to not fully seat.

Benjamin