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I am trying to remove usable parts from a scrapped Columbia AT upper works. I see a set screw in the iron frame to the left of the shaft that carries the reproducer carriage. I have removed it. Where do I go from there? The shaft still doesn’t seem to move and I see no clear way of removing the threaded rod which rides inside the shaft.

I see that the gear on the threaded rod is pinned to the rod. Do I need to remove the pin and gear, then pull the threaded rod out to the right?

Is the set screw I removed all that is holding the shaft on which the reproducer carriage rides?

What is left of the pot metal reproducer carriage sleeve is busted and seized to the shaft as expected. I assume gently breaking it apart is the only way to remove it?

Thanks,
Steve

The threaded rod is called a feedscrew. It rotates within a hollow sleeve. The feedscrew and sleeve are removed by COMPLETELY removing the set screw located at the left end. Once that screw has been removed, the sleeve, gear, and feedscrew can be slid to the left (unless gunk on the sleeve has cemented it in place. Penetrating oil is your friend). Gentle tapping with a wooden dowel on the right end of the feedscrew assembly can help.

In order for the carriage to slide off the feedscrew assembly described above, the half-nut (a little U-shaped metal piece centrally located in the middle of the carriage) will need to be depressed. A toothpick or other non-metallic tool is best for this, but a jeweler's screwdriver works well if you're careful. Push down on the center of the half nut and while holding it down, slide the carriage to the right and off the feedscrew assembly. Of course, if the carriage is swollen and frozen to the feedscrew assembly, you'll need to free it up. If it's already broken/swollen, your idea of gently breaking it apart (try to salvage the trunnion) is probably the only option.

Good luck - -

George P.

Thank you George! Feedscrew, yes feedscrew. I've gotten to the age that I can't remember words anymore. That is wonderful. I will work on it tomorrow. When things are old and stuck it is not obvious that you have everything loose before you begin gingerly trying to make things move. I really appreciate the expert help. I am new to Columbias and am enjoying restoring an AT.

Steve

I had the same problem with my AT, and followed pretty much the same procedure.

I hope you unscrewed the yoke holding the half nut as well.

Bill

Yes, I will be very careful with that halfnut.

Thanks,
Steve

Success! Thanks everyone. I was very happy to learn how to disassemble the Columbia sleeve mechanism on this junked machine before attempting to disassemble my good AT project. Plus I did manage to salvage a few other useful spare parts.

Steve