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.

[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.info/forum/showthread.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. :cool:


Kent in SD

[Andrew]

indeed...

if I read this right, you're trying to enlarge the hole in an aluminium lens board by an extra 7.5mm radius which isn't very much at all. Keep it simple. You can do it with a couple of small hand held files and a little bit of patience. Mark where you want the final edge to be and file down to that line with the edge a file that has an angled edge and do that every few mm so you have something that looks like a gear with the teeth on the inside. That'll get rid of a lot of metal fairly quickly. Than get rid of the residual bits with a file that has a curved surface. You can probably buy a set of small files at the local hardware store for $2.50 and get the job finished in about 20 minutes.

[domaz]

OnlineMetals will do custom metal cutting. Then get yourself a cheap AC (not battery powered) drill and a bimetal holesaw. I've cut 82mm holes in 0.125" aluminum with my $25 drill and it works fine.

[Henry Ambrose]

Thanks Michael!

Kent - if you can't get it done locally I will be happy to do it for you.

[jp]

You've got some different DIY options.

Cheapest option to enlarge a hole would be a nibbler ($10-20 hand tool). This would be ideal for a thin metal lensboard like on a crown/speed, but not so good on a cast or plate metal lensboard.

If you have a drill press or a steady drill, you can get variable sized hole saw bits. Basically a centering drill and a spinning slicer of death that gouges into the metal. A scrap of wood should be used under this to hold the centering bit, and to clamp the lensboard to. If it's a size that can be done with normal non-adjustable hole-saw bits, that's even better. The wood purposed holesaws can cut metal as long as you use oil and don't drill too fast.

A jigsaw with a small metal blade would also do a very nice job. I have a bosch jigsaw which I love. I had a black and decker previously that died the second time I used it.
This will be so much easier than a handsaw or files. Files clog up fast with aluminum.

If someone does it on a lathe, they'll probably have to have a pretty good sized one and switch from the normal 3-tooth self-centering chuck for round items to the 4-tooth non-self-centering chuck for the rectangle/square lensboard.

[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. :cool:
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

[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]

Thanks Michael!

Kent - if you can't get it done locally I will be happy to do it for you.

No problem Henry. While it is great that many here have mechanical inclinations, there are many times when it makes sense to go to those that have the skills and the tools to do it right the first time. I mucked up a perfectly good Toyo lens board trying to do it myself by hand a while back and that my lesson in remembering that I do not work with metal on a regular basis and was clearly outside of my expertise. I am comfortable with wood. Henry has both the correct machine tools and the experience to do it right the first time.

Sometimes the hardest thing to do is to let go and be truthful in the assessment that some of us are better photographers than we are handymen (or handywomen) when it comes to mounting flanges, Packard shutters or cutting lens boards.

[Henry Ambrose]

Having made plenty of near misses with cameras and tools I completely agree about having the right tools. A lathe, milling machine, proper tooling and measuring devices sure make it easier to do it right the first time.

But a rat tail file may work good enough. ;>)

[Two23]

Well, I started out trying my Dremel with a steel cutter, but found it's hard to control. So, I bought a small coping saw and some metal blades. That worked much better. I got a hole cut OK. It's nothing I'd show a shop teacher LOL, but the flange covers it well. End result looks really perfect on my Shen Hao, I think!

Kent in SD

[Henry Ambrose]

Yep, you did it.