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I have a simple issue, but need some info how to fix this. I need to tap a new thumb screw in my Imperial Phonograph.
As you see, the reproducer is all one piece with the tone arm, they don’t separate like a typical Columbia Client Machine. If I remove the stylus bar I’m sure the gaskets would crumble necessitating a full rebuild, so, I need a thumbscrew slightly bigger then what it has. I see a few different sizes on the internet, what, in your opinion, should I buy?

Well, if the gaskets appear about to crumble, it's best to replace them anyway, if you want it to play properly.

The photo is a bit dark; is the front of the reproducer detachable from the back? If the diaphragm is larger than the opening in front, they would have to be, in order to insert it. I seem to see a line between them: is it a press fit? If so, removing the tension screws from the springs, and gently tapping with a screwdriver (after perhaps using some penetrating oil, and giving the tone arm the freezer treatment), might be able to ease the rim off. Of course, if the tone arm/back is pot metal, that might be a problem.

As for tapping the hole: are the threads damaged, or is there part of a broken screw in there? You will probably have to take the bracket off (if you can't remove the front of the reproducer, or the tone arm from the bracket), so you can lay the whole assembly flat for tapping.

That, at least, is my advice; if anyone else has experience with Imperials, they could suggest a better course of action.

- Bill

Bill,
I took better pictures. The tone arm and reproducer housing are one piece, they don’t separate. The stylus bar looks like a typical Columbia piece. What I’m trying to determine, but with no luck, is if the diaphragm is attached to the stylus bar with a screw or just waxed or ? in place. I do have other phonographs but as you know you can’t remove a thumb screw that’s been in a reproducer for ever. I was thinking of using a tap to determine the thread size, I now realize I don’t have one that small.

columbia1spring wrote: Tue May 31, 2022 11:28 pm Bill,
I took better pictures. The tone arm and reproducer housing are one piece, they don’t separate. The stylus bar looks like a typical Columbia piece. What I’m trying to determine, but with no luck, is if the diaphragm is attached to the stylus bar with a screw or just waxed or ? in place. I do have other phonographs but as you know you can’t remove a thumb screw that’s been in a reproducer for ever. I was thinking of using a tap to determine the thread size, I now realize I don’t have one that small.

OK: so it's definitely one piece.

The only way to determine how the needle bar is attached is to remove the screws, take out the outer gasket (no matter if it crumbles - you'll have to replace them anyway), and remove the diaphragm & needle bar.

I'm not sure about checking the size and thread of the hole: I would have to defer to a more experienced restorer. In case you have to eventually drill and re-tap it, it's best to find out the size of the more commonly available thumbscrews. Perhaps sending the whole tone arm/reproducer assembly out to somebody like Wyatt Markus might be advisable.

As I have said, there are others far more experienced with these details than I; I hope they will chime in with better advice.

- Bill

It looks like your reproducer is put together like the ones on my Columbia BI and Open Works machines. They are rebuilt from the front and are the easiest to rebuild of any I have done.
Just fish out the old front gasket and the diaphragm will come out the front when you remove the screws that hold the needle bar to the reproducer.
The depth of the lip that holds the gasket/s in is just the right depth allow the gasket to hold the diaphragm in place.
Install the new bottom gasket, then the diaphragm mounted to the needle bar, then the outer gasket can just be tucked in under the lip and voila, rebuilt!

I can get the thumb screw out for you if you still need it. It is best if there have not been any previous attempts to get it out. That usually makes it more difficult.

Ken Danckaert