Lens Board Drillig

[Wade D]

I have an undrilled board for my Crown Graphic. A Graflex Optar 135mm in a Graphex shutter is on the way to me. Of course I will wait till I get it to determine the size of the hole needed. I also have a drill press and clamp block. My question is will a fly cutter meant for wood work with aluminum? What would be a preferred bit for the operation without damaging the board?
Thanks,
Wade

[ruilourosa]

It will damage your cutter! get one with a titanium tip, not that expensive, they use to be yellow like some black and decker drills, although not that much of a problem!!!

[Rick A]

Most fly cutters use tool steel, should be okay, just use a slower quill speed and feed it slowly. I use hole saws, but I don't think they are as accurate as fly cutters. Is your cutter a single or double bit? Doubles should work easier.

[bdial]

It will work ok, as Rick says, though it might need a sharpening afterword. You might want to use some light oil.
Feed the bit VERY slowly, and make sure the board is securely clamped down. If you have some scrap AL to practice with that would be good.

edit - Just remembered how thin a Graflex board is, you may want to sandwich it between two pieces of wood to support it during the cut, and keep it from tearing out.

[paul ron]

Hole cutters n fly cutters aren't accurate and will make a lousey job of your board, they wobble n are never on center. Better to cut the hole undersized with a hole saw then file it to the finish line.

[Ian C]

The clearance hole for a shutter must be accurate. If you examine the threaded retaining ring for a modern shutter you might be surprised at how little difference there is between the diameter of the treaded shank of the shutter and the outside diameter of the retaining ring.

The hole must be slightly larger than the shank, but must be no larger than necessary so that there is enough material left for the ring to grip the lens board.

Machining a shutter clearance hole is a job best done with a single point cutting tool in milling machine. These have precise bearings that allow no unwanted radial movement (within practical limits) of the spindle as it rotates.

In contrast, a drill press has a much simpler bearing set that allows too much radial movement for precision work. Older drill presses that have seen much use often have bearings that are worn allowing the spindle considerable radial movement. Accurate work is impossible.

If you don’t have access to a milling machine, it’s prudent to send the board along with a precision measurement to a machine shop. If the hole is machined oversize, it will be spoiled for the shutter size you intend.

I machine aluminum boards on a Bridgeport milling machine using a single-point high-speed steel cutting tool. I always take a test cut in a piece of scrap to verify the hole diameter it produces before machining the lens board.

[John Koehrer]

On the other hand, both hole saw and fly cutter will work.
The tolerance on some can be higher than others, in addition, some flanges may have a lip that should insert into the hole to position the lens.

[waynecrider]

I use to take mine to a local machine shop I found.

[rjbuzzclick]

I've done a couple of SG aluminum lensboards-smaller holes with a Greenlee punch and some filing, and one larger hole with a lathe, which worked OK, but the edge of the hole ended up with a lot of burr material that had to be cleaned off.

[Jim Jones]

I've done a couple of SG aluminum lensboards-smaller holes with a Greenlee punch and some filing, and one larger hole with a lathe, which worked OK, but the edge of the hole ended up with a lot of burr material that had to be cleaned off.

A really sharp lathe tool ground to the right angles should make a clean cut. Backing the lens board with scrap material will also help. If you do have a burr, scraping it off with a sharp right angle tool can be quicker and neater than filing. Sometimes a metal ruler works for this.