Cutting metal lens boards

[Harold_4074]

The classic method ("classic" meaning as practiced in a farm workshop 50 years ago...) is to scribe a circle just slightly smaller than the required final diameter, drill a series of nearly overlapping holes (1/8 inch or so in diameter) just inside the circle. Nip out the thin webs between the holes with wire cutters, and then use half-round files of increasing fineness to enlarge the hole until the lens just fits through. The resulting hole may not be perfectly on center, and may have a bit of runout in spots, but unless you are off by more than a sixteenth or so, it won't matter.

Over the years, I must have done a dozen or more like this, and still prefer it to a fly cutter if the board is not easily replaceable. I have also dismounted a handful of old lenses, and most of them had been mounted by this method (the wide flanges make the hole size and shape very non-critical).

Of course, when I had access to a numerically controlled milling machine it was a different story

[domaz]

You've got to be joking. A jig saw?

If you have the boards already or find them on ebay for a few dollars, just bring them to a local machine shop, and wave a 20 at the man. He'll use either a mill and boring head or a lathe. Any other method is a compromise, risky, and will yield poorer results.

I use a jig saw and a hole saw to cut aluminum boards for my Gowland which uses a non-standard lensboard size. My boards aren't warped and all work fine. I just spray paint them black when I'm done. No problem with the paint coming off and I never used any exotic aircraft grade primers or paints.

This is a case where you can make the job as simple or as complicated as you want IMO. If you are worried about 1/10th of a mm precision go to a machine shop, if you just want it to work hack something up yourself and be happy.

[Michael E]

This is a case where you can make the job as simple or as complicated as you want IMO.

Just for a quick trial or for lenses I hardly ever use, I cut lens boards out of matting board. I use a box cutter and some sand paper to clean the edges. Matting board has the added benefit that lenses without flange can simply be screwed into the rag. If the board has the right thickness and fits well into the camera, it is surprisingly sturdy. I can choose black stock or spraypaint it black. So much for low tec.

Michael

[Chauncey Walden]

There may be some disconnect on terminology re "jig saw". In my youth what we generally called a jig saw is now called a scroll saw and what we called a sabre saw is now a jig saw. I have cut many, many boards with a Dremel "jig saw" now called a scroll saw. Now I cut most of them, including aluminum boards, with one of these in a drill press:
http://www.nextag.com/1-Inch-To-6-524646714/prices-html

[eddie]

i put the lens board on the table. add screws to the outside of the board. two per corner (to keep it from spinning) 8 total. then i drill the hole with a hole saw on my drill. simple as pie.

[matthew blais]

I used a circular (adjustable) hole cutter on my technika boards...Costs about $10 and will adjust up to 4"

[Jeffrey Sipress]

There is a very good tool designed for exactly this purpose that I should have mentioned, since I have one. It's called a 'trepanning tool'. It looks much like a fly cutter, but it's a very different design, using a 'drag cut' geometry that avoids the errors and instabilities of the fly cutter. The origional is Val-Cut, made in Switzerland. It's also sold by SPI under their brand. These things make beautiful holes in metal. Not designed for wood at all.- Leigh

Trepanning tools work well only if you are experienced and have a proper machine to use it on. If not, they are very dangerous and scary! While it's possible to use one on a drill press, you really need a mill or lathe. Knowledge of feed and speed as well as coolant is essential. When the cutting tool (never referred to as a 'bit'!) breaks and flies across the room, you need to keep your belly far away.....

BTW, I've worked in machine shops for nearly 40 years and have owned a high precision CNC shop for 25 years.

[E. von Hoegh]

I use the adjustable circle cutter for wood, and a lathe with 4 jaw chuck for metal.
Trepanning a hole in a lensboard a bit much, I think.

I've scribed, sawed, and filed holes in metal boards, and drilled, carved, and rasped holes in wooden boards, and done it well enough that no-one from the Linhof or Deardorff companies would scoff at the work. But I much prefer to use the correct tools whenever they are available.

[Leigh]

Trepanning tools work well only if you are experienced and have a proper machine to use it on. If not, they are very dangerous and scary!

All tools are dangerous if used improperly.

Anyone who attempts a task for which they're not appropriately trained and equipped deserves what he gets.

I use a Bridgeport or a Monarch 10ee, depending on which is free when I need to do the work.

- Leigh

p.s. T&D Maker for 45 years

[Bob Salomon]

There is a very good tool designed for exactly this purpose that I should have mentioned, since I have one.

It's called a 'trepanning tool'. It looks much like a fly cutter, but it's a very different design, using a 'drag cut' geometry that avoids the errors and instabilities of the fly cutter.

The origional is Val-Cut, made in Switzerland. It's also sold by SPI under their brand.

These things make beautiful holes in metal. Not designed for wood at all.

- Leigh

That thing is $150.00 at SPI. How many holes does he want to make? A machinest is going to probably be cheaper not to mention any ruined boards during the learning curve or medical bills from cuts or impacts.