Knurled knob broken off Copal Tension Lever Arm - ACK! Anybody had this before?

[Sparky]

I just picked up a lovely Nikkor M second hand - and as soon as I got it home started playing with the shutter / checking it out and plop! The the knob off the end of the tensioning lever arm falls off!! I pick it up, thinking it must have unscrewed itself (though I never had it happen before) and I could press it back into place pretty easily - though it just seems to fall out again... I can't see well enough behind the arm to tell what the exact deal is - but it looks like these are sort of rivet-fit onto the lever arm... has anyone had this happen before? Any suggestions for self repair (i'm doubtful that's possible) and/or if a decent repair person could fix this???

 

[John Koehrer]

Yep it's riveted. Take it apart(bad idea) and spread the rivet a bit OR use a poodab of epoxy/JB Weld on it. I'd go with the poodab myself.

Believe it or else it doesn't take a lot. With either material just use a toothpick dipped in each part mix 'em on a scrap o' paper & just use the tiniest little poodab you can. Let it cure for the recommended time and Viola(voila) can't speak French

 

[Sparky]

seems like it would be the best idea (?) to modify a standard riveting tool to get the right purchase on the flare end to re-spread... I haven't had great luck in the past with epoxy on formed steel (too slick!)

 

[Sparky]

MAY try the epoxy in the end... but I'm inclined to think that the rotational force placed on the knob might easily break the bond...

 

[John Koehrer]

Regular epoxy may actually be too brittle whereas the JBWeld is softer. The JBWeld is much like a soft metal and can be worked with simple hand tools. I can also be drilled and tapped. In either case if you try the glue route roughen the mating surfaces a bit a light stroke or two with a fine sand paper would do it.
Here's an off the wall idea, I 'm doubtful that it's feasible. If you could get something like a small ball bearing (.5mm?) to fit the end of the knob and apply enough pressure with pliers or clamp of some kind. It may be possible t deform the rivet enough to hold.
Did I say doubtful?

 

[Sparky]

HA! Great minds think alike! I actually came to the EXACT same conclusion myself as a solution...! I was thinking small ball bearing and a layer of (cloth or card) over the other side of the pliers... should be perfect for respreading the rivet.

 

[Sparky]

though actually i was thinking something more like a 3mm ball bearing would have the better curvature - you want to flatten the ends more than you want to increase the size of the I.D...

 

[John Koehrer]

Yer right about that great minds thing. =-)
The only thing is getting enough leverage to actually spread the rivet.
Wonder if a couple of small slots around the perimeter would make it easier. Be tricky with something that size.