tolerences for lensboard hole size for Copal 0

[David F]

I want to get a hole drilled for my Copal 0 shutter. The info. on this site and at Grimes Co. says that the hole for the no. 0 shutter is 34.6mm, which equals 1.362 in. Another width I've seen (also on Grimes site) is 34.7mm.

The machine shop guy I spoke with said that he could drill an exact 1.362 in. hole with his lathe but it would be very expensive. Or he could use a 1-3/8 inch (= 1.375") drill bit for a more reasonable price. He also said that drilling with the bit would put the hole very very very close to the center of the board, but not as exact as with the lathe.

My question.: is a 1-3/8 inch hole acceptable for the no. 0 shutter? And is getting very very very close to the center of the board, but not exactly center, acceptable? In other words, what is the tolerances and amount of play that's acceptable for mounting on a lensboard? I haven't really seen this info anywhere.

Regards, David.

[John Berry ( Roadkill )]

Worked for me on the wooden lensboards I have made for myself. The difference is only.013 . Lens centered in the hole leaves .006 equal distance clearance, or 2 human hairs average, between lens and hole. The clamping surface of the retaining ring covered that much gap easy. With lenses that are designed with rise, fall, shift, and swing. Very very very close is close enough. In fact very close is close enough.

[Joseph O'Neil]

A friend of mine who is a machinist made me a number of lens boards, same thing - 1 .3/8 hole, and other shutter sizes approx too. Worked just fine.

joe

[Ben Diss]

Machinists are perfectionists. Tell him to drill a hole, centered to a tolerance of +/- .015 with a diameter of 1.362 +.015/-0. If he spends more than 5 minutes on the job he misunderstood something.

-Ben

[Emmanuel BIGLER]

No problem as seen from my metric eyes ;-). As far as I can read on S.K Grimes' web site, 34.6 mm refers to the diameter of the retaining ring of a #0 shutter.
The actual hole diameter is supposed to be .2 mm bigger, i.e. 34.8mm to allow .1 mm of play on each side. 1"3/8 is 34.9mm, you'll get .15 mm of play on each side !! Since the retaining ring has a "safety cap" much broader than .5 mm (it is about 1-2mm wide) there is definitely no problem being light-tight even if you'll be on the high side, close to the unacceptable, of the tolerance interval for a precision machinist ;-);-)
Do not forget that the hole should touch the retaining ring, not directly the lens mounting thread (this, only in case you have to re-fabricate a home-made retaining ring).

[John_4185]

As other's have noted, Yes it's okay. In fact, 35mm will do. You could save yourself some money if you have a drill; just buy a 35mm hole saw. Then you will have it around for any future occasion.

[eric mac]

On my wooden handcrafted ( home made) boards, I just drilled the hole as close as I could to the correct size and then just sanded or filed it up to the correct size. The movement of the wood throughout the seasons is more than these close tolerances dictate.

I wouldn't worry too much about being dead center, I think that you would be close enough for your view camera.

eric

[Ted Harris]

If you are talking a metal and not a wood board then there is one reason to machine the hole rather than drill it and that is the potential stress to the metal from drilling that may (repeat may) cause a very slight (probably less than .001mm) twisting that could do something to the flatness/alignment of the lens with the film plane. Yeah, pickjing nits for sure but wanted to get it said. We work very hard to maintain critical sharpness and resolution throughout our taking and processing and yet some small errors in the euqipoment can undo it all.

[Ron Marshall]

I purchased a used, supposedly, #1 Sinar board that was a couple of millimeters tight, so I widened it carefully with a file, in a couple of minutes.

[Alan Davenport]

If you have access to a drill press, you can go to Sears (or wherever) and get a flycutter for probably less than a machinist will charge to drill a hole. IIRC, I paid about $20. I use the flycutter on both wood and metal boards. I can't seem to adjust it for exactly 34.6mm, but as noted close is close enough. One way to get closer tolerances is to cut the hole slightly small, then finish with a Dremel or similar.