Wood Field Camera Repair Question: How to remove the focus knob on the Pinion?

[tdicorcia]

I am in the middle of disassembling a Japanese half-plate wooden field camera. The two focus axles (on which the pinion gears fit) are a little rusted. I'd like to remove them so I can polish them up, as one of them turns very tightly in its wooden channel. I made a tool to remove the outer nut from a Dollar store steel ruler. The larger knob seems to fit on the axle over a square section. It does not pull off. I'm thinking of getting a small gear puller to try and remove it, but thought I would put the question out there before using force. Perhaps it's soldered in place? BTW, when assembled, the whole bed could only be slightly moved. In addition top cleaning the pinion axle I plan on lightly sanding and waxing the wooden sliding surfaces.

[rfesk]

Steel or brass?

[tdicorcia]

It looks to me like plated steel, probably chrome plated. However, the knobs are deeply knurled, so maybe they are plated brass. I don't see any spots where the base metal shows through. I just noticed the picture I took shows a yellow or even bronze-colored cast. That's inaccurate. The axle that the wheel sits on is steel, as I see rust on it.

[RichardRitter]

Knob is probably put on with a locking compound Like LokTight. Plus it is tighten up against the end of threads
One of two things may happen when you go to twist the knob off.
1 It comes off.
2 The shaft breaks right where the threads end.

[rfesk]

Richard has far more experience than I have in these situations.

If it is a brass knob on a steel shaft you may have galvanic corrosion between the two different
metals. IF you are sure it is pushed onto a square shaft rather than threaded on - a gear puller may work.

[Keith Pitman]

If it has Loctite as Richard suggests, a drop or two of Acetone (aka nail polish remover) will soften up the Loctite and make it easier to screw off.

[Conrad . Marvin]

My two cents. Loctite might respond to some heat as well. But if the knob is plated it might ruin your whole day to heat it up too much.

[Eric Woodbury]

Brass does not have dielectric corrosion with steel.

Looks like a square shaft inside a square hole. I would put the nut back on enough to protect the threads. If there is Loctite in there, then follow the advice above, but I doubt there is any. Loctite has a color to it so you can spot it easily. Probably dirt and crap jammed in there. Or corroded steel flakes. So put a little oil on it. Tap on the nut with a small hammer and see if the knob loosens. It would be great if you could somehow hold the knob in a vise (not too tight as this will make the knob grab more, better to simply support the knob with the high mass of the vise) and tap the shaft out of the knob. Go slowly. Don't hammer the knob.

That's my two bits. If you have a machinist handy, have him remove it.

E

[LabRat]

Knob went on, should come off, right??? But you are risking damaging parts by trying to remove, so Plan A is just cleaning up knob in place before possibly damaging it...

You should be able to tell from the inner shaft to knob if a square shaft, threaded knob + shaft, spline, press fit etc, but maybe leave it alone as work there might damage parts/finish...

A usual important restoration decision(s) is what NOT to do...
Don't do anything you don't absolutely HAVE to!!!

Steve K

[tdicorcia]

Wise words here. I thank you all. By removing the knobs I would be able to get to more easily work on the pinion shaft and remove rust that's on it. I may be able to get enough access to achieve that goal without removing the knob. It just means it will be a bit more awkward to work on the shaft. There will be a couple of metal side pieces hanging off both shafts. I'll report back. I was hanging onto the diea that I need to succeed in learning how to disassemble the whole thing, but that's my ego, not my practical side.

BTW, picture of this camera that I hope to get working smoothly...