Cutting a Lens Board

[Two23]

I now have a Petzval lens that I think will work for me. Dang, it's pretty! I now need to mount it to an aluminmum lens board and put it on my Shen Hao 4x5. Lens board has a 3.25 inch reinforcing ring built into the back of it, and the lens will easily fit inside that. Thickness of the metal is 2mm. Exitisting hole is for Copal 1 and is about 140mm. New hole needs to be 155mm. What should I try cutting it with? I could wait to take it to a machine shop, such as a John Deere dealership (tractors/farm implements.) I've taken my cameras there before when I needed some professional but cheap machining done.


Kent in SD

[Ed Kelsey]

I would say chuck it in a lathe...but that probably only works if it's square.

[Leigh]

I would say chuck it in a lathe...but that probably only works if it's square.

A four-jaw lathe chuck will hold a workpiece of virtually any shape.

A lathe is certainly a good way to go, or a vertical mill. In either case a boring bar will do the best job, as opposed to a "hole cutter" of any sort.

Be careful of "hole saws". They typically cut quite a bit oversize, and it's very difficult to keep them centered in an existing hole. They're designed to work on virgin metal where they cut their own pilot hole with a drill.

- Leigh

[Jim C.]

Be careful of "hole saws". They typically cut quite a bit oversize, and it's very difficult to keep them centered in an existing hole. They're designed to work on virgin metal where they cut their own pilot hole with a drill.

- Leigh

An important note about hole saws is that they should be used at SLOW speeds in both wood and metal.
BiMetal saws will cut both wood and metal ( I use with cutting fluid or WD40 on aluminum boards ).

I recently cut a Cambo board to accommodate a lens clamp by enlarging a preexisting hole,
it's not that difficult to keep the hole saw centered, the Cambo boards are flat on the back
so what I did was easy, thin metal boards with a raised lip would need some creative clamping so that
the board isn't crushed.

Measure the diameter of the existing hole on the lens board,
on a scrap piece of MDF find the center, the scrap MDF should be large enough to
accommodate the board and have and area for clamps.

Use a compass to draw the diameter of the existing hole on the MDF,
carefully center the lens board to the drawn circle.
use tape to temporarily hold it in place so it doesn't shift.

On a drill press, center the MDF board with the lens board taped to it by
lowering the chuck with a point tool in it and moving the MDF board till it's centered to the chuck.
Clamp the MDF board and the lens board when you have it centered, use the lowered
chuck with the point tool to hold it in place.
I used a lathe centering tool I made to align the MDF board, but any conical point
that you can put in a chuck would do like a center punch or a counter sink bit, not a drill bit.

Install the hole saw and drill at slow speed till you're thru the board,
drill with light cuts, don't try to go thru in one shot.
with metal use cutting fluid or WD40, none needed for wood.

Clean up the hole with sandpaper or a deburring tool.

It sounds like a time consuming task but all the jigging and cutting took me 20 min.

[Michael Kadillak]

I have had Henry Ambrose drill some lens boards and mount some flanges for me and he does fabulous work at exceptionally reasonable prices and he is among us here at the LF Forum. Henry is a great guy and he will be more than happy to assist you.

Contact him at :

henry@henryambrose.com

[ic-racer]

A metal cutting bit and a Dremel will do it. Not the quickest, but by the time you drive somewhere and back you could have it done.

http://www.largeformatphotography.in...ad.php?t=62723

[John Koehrer]

DUDE,That's like a six inch hole man! Are you gonna have a lens board left?

One o' them sanding widgets you chuck in a drill?

[Chauncey Walden]

I think he got an extra 100mm in there. But in going from 40 to 55mm a jeweler's saw frame saw would be entirely adequate for the task. They are inexpensive and handy to have around.

[Two23]

I think he got an extra 100mm in there. .

Yeah, I'm not used to working with mm. Plus I was out most of last night chasing trains and lighting them up with my flash.


Kent in SD

[Roger Thoms]

Yeah, I'm not used to working with mm. Plus I was out most of last night chasing trains and lighting them up with my flash.
Kent in SD

Millimeters work just like inches, all you need is a measuring device incremented in millimeters.

As far as cutting the hole, lots of way to do it. If you can have a machinist do it that's ideal, but sometime the low tech methods will get you out shooting with the lens faster. I just used a jewelers fret saw to cut a hole in an aluminum board. It was a little tedious and took some time but way less than driving to the machine shop to drop off and pickup the board. Basically a 1/2 hour at the kitchen table and I was done. No the hole isn't perfect but it is totally serviceable and you can't see it unless you take the lens off.

Roger