I gather that "I have a secret" that I haven't seen anyone else ever write
about.
If you buy a couple of Forstner-style wood boring bits, imported Chinese
versions of which are available very cheaply today, you almost trivially can
get absolutely perfect, flat bottomed round holes for lensboard use.
I would not and do not recommend the Chinese-made Forstner bits for heavy
duty, that is, regular day-to-day use. They don't stand up to it. But for
making a couple of lensboards? Absolutely perfect. This includes making
recessed lensboards **out of one piece of wood**. (Admittedly, I did once
make a sample recessed lensboard on the *lathe* (metal lathe, of course),
with nice chamfered walls to the recess, just for sport.)
Just remember to bore the larger holes -- to make the shoulders for rings,
etc, if necessary -- first! :-) :-) :-) And "oh" -- it really is
necessary to use a drill press and low speed; I use 300 rpm. Using a hand
held drill will result in a total mess and is personally dangerous. Don't
drill "through" from one side. First, drill the second side slightly, like
1 or 2 mm (1/16" or 3/32"), then drill through from the first side. That
way, absolutely no splintering. Is that too obvious to mention?
I've been making lens boards this way for years. Consistently perfect, the
first time. Of course, this only works in wood or plastic.
Alternatively, if you're going to use a saber saw to make lensboard holes,
don't try to make your cut along the circumference. Rather, drill a smaller
hole, like 1/2", in the center, then saw *radially*, from the center
towards the circumference. Make about 25 such cuts; it is easy to stop
cutting just clear of the circumference. Then it's easy to cut out the
resulting wedges without sawing across the circumference, and you can
readily finish things into a rather clean circle. This is not as nice, and
is much more work, then using a Forstner bit. But it is much finer than
trying to cut along the circumference, then sanding. Preferably, don't do
this with plywood! Use a new, premium quality, fine kerf / fine tooth
blade.
Don Feinberg ducque@xxxxxxxxxxxxxx
For those who make their own lens boards from wood, it takes only a little imagination to laminate pieces and make your own recessed board. Mine took some time, obviously at least three times as long as making one piece. But time spent this way is time enjoyed. This was for my 90mm Linhof/Schneider Angulon on 4x5. I vaguely recall this is the one where I mounted the lens a little below center so the thing would clear when angled in during installation on the camera. I do a fast cardboard prototype to check clearance before committing labor to wood. Labor is cheap, 1/8" 3-ply is hard to find now.
Someone mentioned elsewhere boring the hole. This is simple in wood, with a saber saw. A perfect circle is not needed, just an approximation that is fine tuned by sanding the high spots until the lens slips in.
And the tip I got from Mr K, Krylon Ultra Flat Camo is the flattest black out there. I always use an ebony stain first, but I'm not sure I can justify that with any rational argument. Bare wood absorbs a lot of spray paint, and maybe I noticed my first board looking glossy like maybe the flat stuff soaked in and left the shiny stuff on the surface (excuse my highly technical paint terminology).
Regards... Dick Gifford
Dave Hornford wrote:
I have a bag-bellows for my 90mm, but find my lack of a recessed lens-board
a bigger hindrance.
Dave
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