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Daniele Minetto
24-Mar-2006, 04:30
Can somebody tell me who's right?
Lensboard hole for a copal #3 shutter: Schneider Kreuznach site: 65,3 mm / J.C. Barnaud on L.F site: 64,2 mm / R. Baker on L.F. site: 65,00 mm .....????? WHAT is the RIGHT size? And what about tolerance?

Richard Kelham
24-Mar-2006, 04:58
I don't have any size 3 lenses at the moment, but I do have a spare lens board for my Linhof awaiting the day...

The hole in that is 65.0mm.

Matt Miller
24-Mar-2006, 05:52
65mm is what I use.

Scott Davis
24-Mar-2006, 07:05
you're talking about a 1.1 mm difference between smallest and largest. All three sizes are well within tolerance. Don't sweat it. I drill my own lensboards for my 8x10, and I've gotten within 2-3 mm of actual size due to various issues. As long as the hole is not so big that the lens is flopping around in it, or it is leaking light, I wouldn't sweat it.

BrianShaw
24-Mar-2006, 07:39
All of the above!

tim atherton
24-Mar-2006, 08:34
http://www.skgrimes.com/lensmount/shutmt/index.htm

Stan. Laurenson-Batten
24-Mar-2006, 09:55
I cut my own boards. The Copal #3 to 65mm or 2.559 inches. No wobble and snug fit.

Ron Marshall
24-Mar-2006, 12:13
Here is a chart: http://www.largeformatphotography.info/lensboard_hole_sizes.html

Michael Graves
24-Mar-2006, 16:46
So where does one find a 2.5559" hole saw?

Ralph Barker
24-Mar-2006, 17:48
"So where does one find a 2.5559" hole saw?"

You drink a 4-shot latte before using a 2.5" hole saw. ;-)

The chart (http://www.largeformatphotography.info/lensboard_hole_sizes.html) I compiled for the home page includes the nearest fractional sizes. From there, it's a matter of sanding or filing to fit. Forstner bits tend to be available in closer sizes than hole saws, and produce much cleaner edges. But, the forstner bits only work on wood or plastic, not metal.

Paul Metcalf
25-Mar-2006, 20:53
Ralph-
You list the through-hole sizes in the chart, but what about the partial routed hole diameter for the retaining ring to set in (wood boards)? And how does everyone cut those (router in router table with some sort of jig)? Thanks.

Ralph Barker
25-Mar-2006, 23:26
Paul - depending on the ring and the type of wrench being used to tighten it, you'll need a rabbet of 1/4" to 3/8" around the back side of the lens hole. That's fairly easy with forstner bits of the appropriate size if you have a drill press. Just set the depth stop, and drill the larger partial hole on the back side first. Then, drill the smaller hole, using the center-pin hole from the larger drill as your center guide. Obviously, the lens board needs to be well-clamped to the table of the drill press. A piece of scrap under the lens board should be used to prevent tear-out.

A router with a guide collar and a jig could also be used - for both the retaining-ring rabbet and the lens hole, actually. If I were making a bunch of lens boards of various sizes, I'd build a jig with multiple slip-in guide plates, one pair for each size combination.

Paul Metcalf
27-Mar-2006, 08:38
Ralph-
Thanks for the answers. One last question. When increasing the hole size in an existing drilled board (e.g. going from Copal 0 to Copal 1 or 3), what is the best techinique? Thanks.

Ken Lee
27-Mar-2006, 10:32
What kind of affordable tools and materials are needed to cut an appropriately sized hole in a piece of wood to make a lens board ?

I'd like to make some off-center boards. The material doesn't have to be exotic, or even wood, for that matter. Just opaque and workable.

William Mortensen
27-Mar-2006, 10:57
Ken- I use Pergo for my lensboards. It's a wood-finish composite material made for flooring. I'd also consider hardwood flooring material or perhaps a high-grade plywood or fiberboard. Solid wood is likely to warp over time.

I cut holes with a cheap hole saw (from Harbor Freight, $3.99 a set on sale) in a drill press. Put a second piece of wood under the lensboard so you don't cut into the metal table of the drill press. The Pergo is pretty tough stuff and it wears out the hole saws after a a few holes (unless you don't mind it half-cutting and half-burning on the way through...) I also use a spiral-cutting bit in the drill press for odd sized holes, and round out any irregularities with a file. All pretty low tech. but the lensboards work great!

Ralph Barker
27-Mar-2006, 12:43
Paul - the size differences between the shutters are fairly large. With an existing smaller hole, that also means that you're working only with the outer edge of the cutting tool, and no benefit from the centering spur or drill. With the lens board clamped well, I've found working very slowly with a drill press (even a cheapie) works OK, whether using a hole saw or a forstner bit. (The edges of the forstner bit are self-guiding, to an extent, anyway.) Hand drills are more problematic, as either tool will try to skip across the board.

Ken - hole saws are relatively inexpensive, but may require more filing or sanding to get to the right size. Forstner bits come closer to some of the sizes, but cost a bit more. Lee Valley and some of the other online tool outlets carry a better size selection than most local hardware stores. The least expensive method would be to draw the circle with a pencil compass, drill a pilot hole with whatever you have at hand, and use a coping or jeweler's saw to actually cut the circle, filing any gross irregularities afterward. Great precision is not really required. A thin rubber gasket behind the shutter can be used to both reduce spin and eliminate light leaks all but the largest of gaps.