Strange COPAL 3

[imagecom]

Hello all,

Recently I acquired a copal 3 shutter thinking that it has only one thread mount. Sadly (or not), when I received it, it turns out the
hole is only 55.2mm wide.
Has anyone had an encounter with this size and what is it used for? Can the inner ring be removed (Please see photo)?

[Keith Pitman]

A 3S? The front and rear threads would be M56-.75.

[imagecom]

Thank you for a quick reply. It looks that this is even smaller. it's 52.5mm if I am measuring right, but definitely not 56mm, I can't be wrong by that much.

[Leigh]

Thank you for a quick reply. It looks that this is even smaller. it's 52.5mm if I am measuring right, but definitely not 56mm, I can't be wrong by that much.

Threads are defined by the outside diameter of the male thread.

If you measure the internal diameter of the female thread, you must add twice the thread depth.

- Leigh

[imagecom]

I know, Leigh, but I was stupid not to ask the diameter size before I bought it, assuming that copal 3 is a copal 3 (M62-0.75, if I'm right).
My question was, now that the damage has been done, can I remove that ring with red dot as threadlocker and end up with an usable thing or will the springs start flying at me if I do that?
Thanks once more.

[Dan Fromm]

Springs won't fly if you remove the face plate, but the tube won't come with it.

Here's the stupid question of the day: is the front tube threaded internally? I ask because I have a Seiko shutter with unthreaded front tube in the drawer.

[Leigh]

I know, Leigh, but I was stupid not to ask the diameter size before I bought it, assuming that copal 3 is a copal 3 (M62-0.75, if I'm right).

The external (mounting) thread of the Copal 3 is M61-0.75 per the instruction sheet.

The mounting hole diameter is 64mm + clearance.

- Leigh

[Keith Pitman]

Meanwhile, back at the original poster’s question . . .

Imagecom: You’ve given two different measurements: 55.2mm and 52.5mm. Which is it? And, as someone pointed out, the thread diameter is measured from the bottom of the thread. From where are you making your measurement? I still think you have a 3S.

[pgk]

I have a 58mm (M58 x 0.75mm) filter cap screwed into the back of my Copal 3 shutter to protect the shutter blades .....

[B.S.Kumar]

Back to the OP.

I've encountered similar issues, in one case with a modern black Copal 3 shutter. The aperture scale started from f/6.7, and I found out that it was for a Fujinon 250mm f/6.7 lens. I have another Copal 3 or 3S shutter (I forget which), that has the standard thread on the rear, but the front is not the corresponding thread.

Kumar