Sprocket Pin for Canon F-1 old

Dartz

It's a long shot, but someone might have an idea.

The sprocket pin on my Canon F-1 fell out while I was changing film rolls a few days ago. There's enough friction in the system that the film still advanced to the end of the roll - so the problem only became obvious at the end when it advanced through to 39 exposures and kept going.

By which time the missing grub screw had probably long been hoovered up.

I'd been hoping to use this thing at Kaizokucon Friday week, but if I can't replace this I'm goosed.

eBay's coming up negative on spares for something so 'odd' and I need to find a similar part, or come up with a clever solution for a grub screw that'll fit in it.

It's a big, distant ask, but has anyone a line on something compatible?


EDIT: Although I did find someone who had the parts 'on the shelf', the people who had them either wouldn't, or weren't able, to sell them. So I've got a body on the way from eBay to use as a part's donor. I'll post details of what exactly broke once I have the repair done.

Dartz

Finally got this Fixed. And because I utterly hate the "I have a problem. Fixed it, never mind" posts that fester across the internet. Here's how it was fixed

The symptoms were as follows:

The rewind button refused to enage. After some work, it latched into place and it was possible to rewind the last roll. Another roll was loaded and shot through apparently normally. The rewind knob wound forward with each shot. It wasn't until the '36' exposure can wound past 39 that a problem was obvious.

The film rewound normally.

On development, the negatives produced had the individual exposures spaced further apart than normal. The final 4-5 exposures on the roll overlapped with each other by an increasing amount. The final 'exposure' was basically 5-6 repeated exposures on the same point.

Inspection revealed that the winding sprocket was turning freely when it should have been locked in place. This was dissambled and it was discovered that a screw had gone missing.



The axle on top came from the existing camera. The axle on the bottom came from the donor camera. A small screw is missing on the top piece, from the bottom of the shaft. This screw engages with the toothed piece shown below (Taken from the repair manual)



It locks the winding sprocket axle to the clutch normally, ensuring the film advances the correct number of perforations to properl space out exposures. To rewind the film, it's pushed up to disengage the clutch, which lets the film wind back freely. It re-engages the clutch when the wind lever is pulled.

If the screw backs out, it'll either seize the clutch so the rewind can't engage, or it'll pop all the way out, release the clutch again and go missing when the rewind is finished.

There is enough friction in the film advance that even the spool can advance the film against the usual tension. The spool rotates slightly more than the advance sprocket to keep tension on the film - so it'll move a little but further with each winding than it should.



The get the axle out, the bottom cover needs to be removed. The battery cover needs to be taken off, which also unlocks the bottom cover. The upper screw locks the sprocket into place in the axle so they rotate togeter. Both axle screws need to be removed, then put aside to somewhere safe.



The axle can then pop straight out the bottom once both top and bottom screws are removed. The top plate of the camera including the shutter knob and winding lever do not need to be removed. (Unlike what the repair manual tells you to do).

Do not try to wind the camera forward, it'll lock up halfway through the stroke and I don't know if this'll damage it.

Refitting it is basically the reverse. It pops back in. Make sure to move both metal levers out of the way with the tip of your screwdriver. It should slot all the way home on its own.

Fit the upper screw first. This locks the sprocket to the axle.

Advance the spocket slowly to line up the gaps in the clutch, with the hole in the bottom of the sprocket. This will let you get the spare screw into place inside the sprocket. There is a small unthreaded piece on the end of the screw that will let it sit in place in the clutch so it will be fairly easy to put it back together.

Check it by winding the assembly forwards. Try push the sprocket back and it should lock. Push the rewind button and it should spin freely forward and back. Cock the shutter with the advance lever and the clutch should re-engage.

And that, as they say, is that.

Note: The repair can be made without removing the axle - just by swapping the clutch screw from the donor camera in all of five minutes or so. It was removed in this case to inspect it and make sure the clutch screw had properly fallen out, and had not broken off halfway with some of the thread still engaged, and that the new clutch screw would fit. Both cameras came from the same production year, but it was still possible that tolerances would be different, or that there would be changes along the way.