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Correct tool for set screws, rangefinder arm (Crown Graphic)

 
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Nils_pn



Joined: 08 May 2025
Posts: 3
Location: Sweden

PostPosted: Thu May 08, 2025 10:07 am    Post subject: Correct tool for set screws, rangefinder arm (Crown Graphic) Reply with quote

Hello,

After having had my eyes on a Graflex 5x4 camera for a few years, I’m super happy to finally have gotten my hands on one. It is a Crown Graphic with a side mounted Kalart rangefinder. Unfortunately, the rangefinder is incorrectly calibrated. In fact, the arm is incorrectly installed, as it is forced beyond its possible movement when attempting to move the rails all the way back.

I’m trying the reset it, but I do not have the correct tool for the two set screws. I don’t even know what tool to look for. It looks like the driver tip should be a straight cross, and not tapered like all the Philips and JIS drivers I’ve seen. I think someone has already been at it with an incorrect screw driver, as one of the screw heads is partly worn down. The cross indentation is so deep, however, that it should still work fine with the proper tool.

Does anyone know what sort of tool I should be looking for?

Best wishes,
Nils
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hsandler



Joined: 27 Apr 2016
Posts: 37
Location: Ottawa, Canada

PostPosted: Fri May 09, 2025 3:56 am    Post subject: Reply with quote

The Kalart service manual describes them as Bristow screws, but I had no luck finding anything about those.

https://phsc.ca/repair/Kalart/kalart_rangefinder.pdf

I had to adjust the set screw on mine and recall using a Phillips screwdriver, and I managed to break the head off the screw when I retightened it at the end. It’s soft brass. Please be careful.
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Nils_pn



Joined: 08 May 2025
Posts: 3
Location: Sweden

PostPosted: Fri May 09, 2025 2:45 pm    Post subject: Reply with quote

Thank you! I didn’t have any luck finding something when googling Bristow either.

I’m afraid a Phillips screwdriver will most likely not work in my case, given the state of the head. A flathead screwdriver seems to get a better grip, but I’m really worried that I’ll ruin the screw.

Provided I can get it out, do you think it would be possible to find a replacement with another head, or is that out of the question?
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hsandler



Joined: 27 Apr 2016
Posts: 37
Location: Ottawa, Canada

PostPosted: Fri May 09, 2025 4:45 pm    Post subject: Reply with quote

Actually, as I recall now, I think I may have just gripped an exposed part of the Bristow screw that was above the level of the screw hole with pliers. You don't have to remove it; just loosen it enough to turn the shaft inside, then retighten. I broke the screw after retightening too much, so at least my rangefinder is useable; just not adjustable in the future. The instructions I followed for calibrating the rangefinder were on Jo Lommen's website.
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Henry



Joined: 09 May 2001
Posts: 1647
Location: Allentown, Pennsylvania

PostPosted: Fri May 09, 2025 7:05 pm    Post subject: Reply with quote

Probably Bristol screws. McMaster-Carr lists them here:
https://www.mcmaster.com/products/bristol-screwdrivers/. They seem to be real oddballs. Good luck!
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Henry



Joined: 09 May 2001
Posts: 1647
Location: Allentown, Pennsylvania

PostPosted: Fri May 09, 2025 9:24 pm    Post subject: Reply with quote

Nils_pn wrote:
Thank you! I didn’t have any luck finding something when googling Bristow either.

I’m afraid a Phillips screwdriver will most likely not work in my case, given the state of the head. A flathead screwdriver seems to get a better grip, but I’m really worried that I’ll ruin the screw.

Provided I can get it out, do you think it would be possible to find a replacement with another head, or is that out of the question?


On p. 18 of the Kalart instructions, screw MS-21 is listed as a 5-40 x 1/8" set screw. McMaster-Carr lists a variety of head styles on this page: https://www.mcmaster.com/products/machine-screws/
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Nils_pn



Joined: 08 May 2025
Posts: 3
Location: Sweden

PostPosted: Wed May 21, 2025 5:42 pm    Post subject: Reply with quote

Amazing, thank you!

I have managed to remove the screws using a flathead screwdriver and being very careful. Given the information you just gave me (5-40 x 1/8" set screws), would that be enough to find replacements? Perhaps this: https://nettorc.com/en/p/8f32db467af9461fb334a6830109339c/stoppskruv-5-40-x-18-in?srsltid=AfmBOooRfW8G_q46qfMqdp5NNEVubUgg8PcIb59IevPGm1XohiX0e-Ox

or this: https://www.accu.co.uk/imperial-cup-point-setgrub-screws/31039-SSU-5-40-1-8-A2

I feel replacing them would be the simplest solution, but I'm concerned the threads won't be compatible....?

Henry wrote:
Nils_pn wrote:
Thank you! I didn’t have any luck finding something when googling Bristow either.

I’m afraid a Phillips screwdriver will most likely not work in my case, given the state of the head. A flathead screwdriver seems to get a better grip, but I’m really worried that I’ll ruin the screw.

Provided I can get it out, do you think it would be possible to find a replacement with another head, or is that out of the question?


On p. 18 of the Kalart instructions, screw MS-21 is listed as a 5-40 x 1/8" set screw. McMaster-Carr lists a variety of head styles on this page: https://www.mcmaster.com/products/machine-screws/
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Henry



Joined: 09 May 2001
Posts: 1647
Location: Allentown, Pennsylvania

PostPosted: Wed May 21, 2025 6:31 pm    Post subject: Reply with quote

Looks like either of those sources would work. I like the ACCU example, as it clearly shows the hex key opening. Also, it costs less. Good luck, and let us know how it turns out!
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