The 50 mm holesaw sounds like the one. But what I’d do is take a piece of scrap material and drill a test hole, then you’ll know for sure. You’re 1.875” hole saw and a drum sanders is certainly an option.
Roger
The 50 mm holesaw sounds like the one. But what I’d do is take a piece of scrap material and drill a test hole, then you’ll know for sure. You’re 1.875” hole saw and a drum sanders is certainly an option.
Roger
Best way to make a lens board hole for any lens is on a lathe with four jaw chuck. Once the proper size hole is done, drilling the holes for the flange is not as easy as it appears.
Bernice
I make custom 3D printed lens boards for all my lenses. If you don't like the black plastic look, you can always glue a wood veneer on the front (I've done that too)
I have a few scrap sheets of 6x6 aluminum plate, about the thickness of a lens board. I always make a test hole in one of them. This one won't be any different than any others in my work process. Test, test, test (a variation on "measure thrice, cut once").Originally Posted by Roger Thoms
Best,
Dennis
First off, my experience has been pretty much all with older gray "Norma style" lens boards. First off I place the lens board on a Granite Surface Plate (bilateral tolerance +/- 0.0001). Few of the lens boards that I checked and looked to be flat were in fact "perfectly" flat, especially the ones that were previously cut. Even some OEM uncut Sinar gray lens boards that I acquired were not perfectly flat. Since these OEM boards haven't been manufactures since 1970, in the 50+ some years that they have been stored, whose to say how they've been handled or if even dropped.
First thing I do is to get the lens board to be "perfectly" flat, actually quite easy once you get the hang of it. Overcorrection the greatest problem since it is so very easy to do. For cutting the holes, I use modified Forstner bits. I use the ones with the saw teeth around the perimeter. The 2 metal "bridges" between the center of the drill and the outside cutting teeth I ground down to a little more than the thickness of the lens boards, so only the center "drill" and the outside cutting teeth do the cutting. Trick is to slowly, I mean really, really slowly cut the hole and to use Aluminum cutting fluid. Distortion from heat eliminated. Lens boards rechecked, after cutting the hole, and are undistorted. Circular hole in the lens board checked and also undistorted. Before cutting the hole, I very securely clamp the lens board to a 1/2" sheet of PVC and secure it to the table of the drill press.
Before I used to just drill a lot of holes inside the hole to be cut and then with the lens board in a vice, file the opening round. Once I got the Granite Surface Plate, I checked my lens board when I was finished, and it was "warped", but too small for me to measure so probably not enough to matter in practice. To hold the lens board when I was filing the opening, I repeatedly would secure it in a vice in different positions, and I think this procedure caused the "warping". Also maybe the filing?
FYI: I have and use 3 OEM carbon fiber Chamonix lens boards which came with pre-drilled holes. Placed each of them on the Granite Surface Plate and all 3 were "perfectly" flat.
The hole saws transfer a lot of torque to the workpiece as the entire diameter has teeth that are cutting/grabbing during operation and potentially distorting board... And the clamping has to be very secure to hold down board which also can tweak it... Then there's heat generated and work hardening while cutting... So not as easy as it looks...
With a boring bar, there is a single cutter insert held steady in a mill that requires much less force to go through material... Or as Bernice sez, on a lathe where there is just the sharp cutting tool cutting through...
Be careful if trying some operation on a drill press, as they spin too fast for most of this type of boring, and the piece can break free of clamping creating a very hazardous situation...
Steve K
If the lens board is not absolutely stable with zero ability to shift or move as the hole saw is cutting, there will be a disaster if what is used to stabilize the lens board lets go.. That lens board can become a lethal projectile. One of the harsh lessons from working with BIG machine tools, item being worked on can NEVER get away from the set up.
That said, hole saws and similar produces a LOT of friction during cutting, this results in a whole lot of torque that could cause a long list of problems. While a hole saw can and does work for making holes in a lens board, absolute awareness of what can and will go terribly wrong must be accepted.
Im fortunate enough to have a lathe in the garage to do with with ease, and controlled precision. IMO, it might be better in many ways to pay an individual with the proper skills and tools to get this done properly. The results are usually better and the risk of injury greatly reduced.
Bernice
Agree 100%. My father was a self employed carpenter when I was growing up. He showed me how use the table saw in our basement when I was years 8 or 10 years old. Vividly remember some 60+ years ago him showing me how a board being fed into the saw blade can become a lethal projectile... he fed a 2x4 into the saw blade and standing on the side let go of the 2x4. I saw it "fly" to the other end of cellar.
When I cut my lens boards, they were absolutely clamped to the drill's table with 2 back-up "plates" bolted to the table acting as a back-up even more permanent clamp. After rock climbing for about 25+ years, having one back-up anchor was the absolute minimum - whenever possible rigged up a back-up anchor to the back-up anchor. Carry that mindset over when working with "table top" power tools more and more as I grow older and older. Gave up using a Ramset 22 (or 45?) caliber nail gun that I inherited from my father several years ago, when I just didn't feel safe using it anymore.
Agree that using a boring bar the better way to go, but the Forstner bits were all I had at the time. There is a Harbor Freight store near by, but I just don't trust any cutting tool that is sold at a bargain price. Did once look at one of their boring bars, but it seemed to be poorly machined, so put it back up on the shelf.
“... Gave up using a Ramset 22 (or 45?) caliber nail gun that I inherited from my father several years ago, when I just didn't feel safe using it anymore.”
When we moved to our new warehouse, 20+ years ago, we were putting up metal shelving against the walls. After assembling one of them they just weren’t stable enough. Since the Ramset 22 was mine I crawled between the shelves and fired it.
My ears were ringing for the next week!
If you're going to hole saw a lens board, setting it up in a Bridgeport milling machine using a Kurt milling vise and related set up tooling is likely the best-most stable way other than using a four jaw chuck on a lathe.
Drill press works, IF the lens board is absolutely clamped and proven to be absolutely stable set up.
Do not push the cut-feed rate as the higher the feed rate, the greater the forces involved with cutting are. Other deathly important detail, use SHARP cutting tools of known high quality. This makes the BIG difference in cutting forces involved and allows the chance to produce a clean cut, good finish and hole accuracy.
Emphasis on how lethal using cutting tools can be is often not appreciated until a serious or even fatal injury occurs.
Bernice
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