Topcor -> M42 Conversion Question

[Univer]

Hi All,

A quick question, if I may, arising in connection the RE-Topcor -> M42 conversion (remounting) process.

I have three Topcors to convert, and I am currently awaiting delivery of the new mounts. I had a spare few minutes the other day, so I thought I would try loosening the lenses' mount screws (having read that Topcor screws are sometimes very stubborn).

Well, you can probably see where this is going: eleven screws loosened with no problem. The twelfth, however - well, let's just say that the head is now so damaged as not to be readily removable. I plan to Dremel it out - no other choice, really - but that will leave this lens, of course, one screw shy of the proper number.

In the short term, I suspect that I will be able to use the lens in question with the mount secured only by the three screws. In the longer term, I would very much like to find a replacement for the missing fourth.

Hence my question - questions, I suppose. Does anyone happen to know the correct screw size (slotted) for this application? And can anyone suggest a good online source for the replacement screw? I would gladly buy a reasonable minimum quantity, and I'd be happy to buy a screw assortment if necessary.

If all else fails, I may pay a visit to a local watch repair establishment, just to see if the folks there might have a usable replacement screw in the parts bin.

Thanks for your help!

Cheers,

Jon

[mo]

Do you have a photo of what the screw looks like?

[Kathmandu]

I am borrowing this image from another site.

Is it one of these slotted ones? Have you found one yet?

[Univer]

Hi,

Profound apologies - I had forgotten to check in on this thread. Many thanks for the replies.

The screw is indeed one of the slotted style. They look so quiet and unassuming in a photo like that one; it's only when you actually take a screwdriver to them that their true nature comes out.

Because my M42 conversion kits are probably still a couple of weeks away from being delivered, I haven't actually taken out any screws - just loosened them. But I can certainly remove one, measure it, photograph it - whatever might be helpful.

Cheers,

Jon

[John Shriver]

Just pulled one to check. M1.7 metric.

Here's a discussion of JCIS screws:

http://www.buonaluce.com/JCIS.pdf

One source of the screws, North West Short Line (http://www.nwsl.com).