Cutting a hole in a lens board?

[Dave Dawson]

Hi, Can anyone suggest the best tool to use to cut a hole in a metal lens board to fit a Copal 1 lens please?

Thanks Dave

[Havoc]

First mark the center and protect the visible side with something like masking tape. Best would be a lathe. Next I'd use a mill with a rotary table. Otherwise the old school way: marking out with a compass, drilling holes inside (a bit from the marked out line), sawing between the holes and then with a lot of patience and a half-round file filing just to the marked line. If you have a large cone drill then drill close up to the marked line and file the last bit. You need to file as a cone bit leaves a conical hole in something a thick as a lens board.

[malexand]

I use a Hole-saw and a drill press. Make sure the board is clamped tightly to a backer piece of wood. Go slow, use some cutting oil (or any oil really). Aluminum is soft and will cut pretty easy. Wear gloves.

[Greg]

1. First I mark the hole size on the back of the lens board or on the front which has been covered with white masking tape.
2. Drill a small hole just inside of the marked circle
3. Using a small Craftsman or Dremel jig saw, I very, very slowly cut out the hole just inside of the marked circle
4. Finally mount the lens board in a vice and file out the final circular opening.
Have done this with many OEM Sinar boards. Secret is to cut out the hole with the jigsaw very, very slowly. My blades are made for cutting wood, but work fine with cutting out holes in aluminum lens boards. Have yet to have a blade break. Blade is thin Kerf for "cutting hard or soft wood and plastic 5/32"-1/2" thick". 18.5 TPI (teeth per inch). Previously drilled many holes just inside the marked circular opening and round filed the final opening. The above procedure takes way less time and really cuts down on the final filing time.

[Drew Wiley]

I wouldn't recommend a jigsaw, and I sold the best of the best, $700 apiece. It's hard to cut a small hole diameter accurately without a narrow blade, and narrow blades are the most likely ones to snap. Good lensboards aren't ordinary aluminum, but relatively resistant die-cast alum. alloy. But if you choose to do so, firm clamping and eye goggles. But I think Greg is using the term jigsaw differently than me, meaning a small bench device rather than a portable jigsaw. Blades can snap in that case too, so have protective eyewear, and also beware of the possibility of metal splinters to hands. I greatly prefer a fly cutter on a serious drill press, unless you have a milling machine.

[Leszek Vogt]

A two step solution from me. Cut out the appropriate size hole in a decent quality plywood with a jig saw or saber saw. Might have to follow up with a curved file, till it's exactly the size you want. Naturally, the plywood piece needs be somewhat larger to accommodate the next step.

In the next step you'd use a router with a "follow" bit similar to this: https://www.amazon.com/Bosch-85680M-Carbide-2-Flute-Straight/dp/B000CNIL2E/ref=sr_1_94?keywords=follow+router+bits&qid=1570296747&sr=8-94

Anyway, smaller bit like 1/4" or so would be better than 1/2" to keep up with the contours. Just following the walls of plywood shouldn't be difficult. To prevent the router from skating all over the place, start slow and take out small amounts of metal at a time (like 1/16" ?)....till you have a circle that you desire. Good carbide bit will chew up the alum/metal in no time.

It's a given that you have to line up the hole in plywood accurately and take usual precautions with eye protection and clamps to keep the work solidly in place.

Les

[Drew Wiley]

No, no, no, Les ... That's a bit for Formica, and you risk the carbide tip flying off like a bullet at router RPM speeds. I've seen it happen. Take it from someone who handled one of the largest Bosch dealerships in the country for over three decades, and by far the biggest dealer of Freud in the entire country. Bosch now owns Freud. A correct alum. bit has a different type of carbide, a negative rather than positive rake angle of carbide entry, and costs about four times as much. If it were ordinary soft alum. plate, you might get away with it; but for sake of general discussion, most official blank lensboards are diecast, and much harder. For the record, I own and use all these kinds of bits, so understand the distinction quite well.

[Eric Woodbury]

I've always used a hole cutter

https://www.amazon.com/General-Tools-55-Cutter-Adjustable/dp/B00004T7P1/ref=asc_df_B00004T7P1/?tag=hyprod-20&linkCode=df0&hvadid=309813767497&hvpos=1o2&hvnetw=g&hvrand=8869995019922775761&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9031644&hvtargid=aud-801381245258:pla-384684125741&psc=1

In a drill press. Go slowly. Clamp everything firmly. Can't simply hold with your hands. Keep the cutter length as short as possible. It will make an intolerable sound as you cut. Wear ear plugs. Cut half way, then flip it over and cut the rest.

Be careful, always

[Drew Wiley]

There are two sizes of those General fly cutters, both adjustable per diameter. I tightly clamp the lensboard to an oversize wooden board using short wood screws with little rubber gaskets, to prevent marring the lensboard edges. Then the larger wooden board is firmly clamped to the drill press platform. Always use low RPM and cutting fluid when working with either a fly cutter or large metal-cutting holesaw.

[Greg]

But I think Greg is using the term jigsaw differently than me, meaning a small bench device rather than a portable jigsaw.

You are right, it is a small portable bench device. Craftsman (new & still in sealed box) that I picked up at a garage sale for maybe all of $20. Actually wear a pair of CU glasses with a pair of safety glasses in front of them. Tried to use a pair of leather gloves but lost the touch/sensitivity of being able to guide the lens board very, very slowly along the circular cutting path. The front of the blade (teeth) to the back is less than 2mm, so cutting the circle doesn't cause a lot of side pressure/torque? on the blade. It can take me, guessing here, 10-15 minutes to cut the whole because I am feeding the material ever so, so slowly.

[pendennis]

I use a 1 5/8" metallic hole saw on my drill press. I already had jigs made up for various board sizes. I center punch the lens board, then start the pilot hole, and use 3-in-1 oil to lube the cut.

The hole is just a bit undersized, so I use a portable sanding drum on a drill to enlarge and smooth the edges of the hole, test fitting every second pass.

Works right every time.

[Leszek Vogt]

No, no, no, Les ... That's a bit for Formica, and you risk the carbide tip flying off like a bullet at router RPM speeds. I've seen it happen. Take it from someone who handled one of the largest Bosch dealerships in the country for over three decades, and by far the biggest dealer of Freud in the entire country. Bosch now owns Freud. A correct alum. bit has a different type of carbide, a negative rather than positive rake angle of carbide entry, and costs about four times as much. If it were ordinary soft alum. plate, you might get away with it; but for sake of general discussion, most official blank lensboards are diecast, and much harder. For the record, I own and use all these kinds of bits, so understand the distinction quite well.

I guess we just disagree, Drew. The bit that I showed was meant as an example. Although Freud and Bosch are great cutters, however I have more respect for Porter Cable, Paso Robles and even Amana. There was a place in Fla that made really good ones, that starts with "C", though the outfit may have been sold ? Whiteside has always been consistently good.

Anyway, I'm talking from experience and doing various projects....and I'm not into selling bits or machinery.

Les

[Drew Wiley]

It's not about brand preferences, Les. You miss the point entirely. It's about basic safety . Wood bits and Formica bits are not engineered for aluminum!!!! They're carbide-tipped; and I've seen those tips fly off and get embedded in a wooden post clear across a room just like a bullet. Bits intended for non-ferrous metal are micro-grained SOLID carbide with a completely different kind of rake angle. I do not believe any of the brands you mention actually make those, but all buy and relabel them from two specialty mfg. Porter Cable never made bits, just labeled them. Whiteside is a cheapo import. Amana has a huge selection, but a rather poor fill rate to dealers; a web search might work. Please don't offer reckless advice on a subject like this. I've seen some awful injuries over the years. And if it's diecast, it shouldn't be routed at all.

[Peter De Smidt]

I use a solid carbide, micro-grained, curved-edge pattern bit. Actually, I've used most of the methods mentioned, and, with care, they all work fine.

[Roger Thoms]

Drew, are you sure about Whiteside, I thought they where US made.

Roger

[Drew Wiley]

I should have double-checked that one, Roger. I've been retired for almost 3 yrs, and am a bit out of the loop now. It's a bit complicated because many of these companies buy certain things from one another, and also offer more than one line of quality. But what I really wanted to say is that an easy way to smooth the hole is with a simple sanding drum in the drill press.

[Drew Wiley]

Yeah, Roger; I might have got my foot in my mouth on that Whiteside comment. They remind me of Nordic out here - make some things, yet distribute quite a few specialty things from other sources. Some of the bits were patented under other names at one time in NC, so they might have bought the rights. And some items look distinctly Euro mfg. I had other sources for many of the same things. Omsrud out here is also a similar marketing model, but are themselves the primary maker of long spiral cutters. Most solid carbide rtr bits in this country are made by Velepec in NY. Freud Industrial (Italy) has about 20 times as much as the division most people are familiar with. But I'd sure like to know the source of Festool's rtr bits - the carbide quality is amazing. Their drill bits etc are made by Fitch, Austria, and super-durable.

[aclark]

Reading through this thread makes me realise how lucky I am using wood not metal to make my lens boards. With wood you can cut a hole out in minutes using nothing more than a sharp knife.

Alan

[Ron (Netherlands)]

Depends on the size of the hole. For smaller holes I prefer a hole saw - have quite some different sizes for that. For the bigger ones a saw cutter.....
I have hole saws for metal and some that only cut into wood.

[Havoc]

Reading through this thread makes me realise how lucky I am using wood not metal to make my lens boards. With wood you can cut a hole out in minutes using nothing more than a sharp knife.

Alan

Depends I guess. I'm never comfortable working with wood, always get tripped up by the grain. That's why I prefer metal to wood.

[Roger Thoms]

I should have double-checked that one, Roger. I've been retired for almost 3 yrs, and am a bit out of the loop now. It's a bit complicated because many of these companies buy certain things from one another, and also offer more than one line of quality. But what I really wanted to say is that an easy way to smooth the hole is with a simple sanding drum in the drill press.

My problem is I don’t trust any of these companies, it’s often hard to tell where thing actually come from. I do have some Whiteside bits and have been happy with them. Never used them on aluminum.

As far as cutting a hole in a aluminum lens board there’s always the lo-tech method of using a jewels saw and half round file or sanding drums on a drill motor. Bottom line is that there are many different ways to do it.

Roger

[Drew Wiley]

I eventually found it easier to use a carbide-tipped holesaw on the drill press simply because so few sizes of a set diameter are needed to cover all the common shutters. You have to test them for actual diameter - they're not precision devices. And they don't leave the cleanest edges; but that's easily cleaned up any number of methods. I also had the ability to purchase all these kinds of things at substantial discount, or even to acquire them as free samples. I seldom use a jeweler's saw, but do have one. In terms of files, the most versatile one I own is a Formica file, also sold for plexiglas and ski edges, great for soft materials like aluminum or brass because it doesn't clog up. But it's flat, so something else is needed for the hole. Just silicon carbide emery cloth wrapped on a stick works fine for that; but since I need an excuse for having purchased a bunch of sanding drums, I tend to use that method instead.

[Jody_S]

Dremel rotary tool with appropriate bit, and the Dremel circle cutting attachment (https://www.homedepot.com/p/Dremel-Circle-Cutter-Attachment-3-4-in-to-12-in-Diameter-678-01/202713389). With some practice, I now regularly cut holes in wood accurate enough to screw lenses into the wood directly if I don't have the flange.

[LabRat]

Boring head on a mill works best, so ask any machinist...

Steve K

[LabRat]

Dremel rotary tool with appropriate bit, and the Dremel circle cutting attachment (https://www.homedepot.com/p/Dremel-Circle-Cutter-Attachment-3-4-in-to-12-in-Diameter-678-01/202713389). With some practice, I now regularly cut holes in wood accurate enough to screw lenses into the wood directly if I don't have the flange.

Only for wood or maybe plastic, but not for metal...

I have a circle cutting guide for a router, and if set up correctly, makes really nice holes in wood!!!

Steve K

[Paul Ron]

undersized hole saw, then a good bastard file will take you right to your finish line.

[Jody_S]

Only for wood or maybe plastic, but not for metal...

I have a circle cutting guide for a router, and if set up correctly, makes really nice holes in wood!!!

Steve K

I've done aluminum boards with a sharp bit, have to be careful not to load the bit with chips though.

[Drew Wiley]

Gosh. Why not use a horse rasp if that is all you've got. Why not a spiked ball from a medieval battlefield? I guess all kinds of things could work. But some methods are far more efficient than others, and safer.

[Gary Beasley]

Another good tool for cutting the aluminum is a scroll saw. The blades are very fine, you start the cut by drilling a hole inside the marked circle and feeding the blade through. Once mounted cut following the circle pattern which can be marked directly on the metal with a scribe or printed on paper and sprayglued to the metal. Cut just inside the pattern and clean up the cut with a half round file or drum sander.

[alt.kafka]

How thick is the aluminum plate that you're using for lens boards? Are you anodizing or painting them?

[Greg]

Students in a machine shop class at our town's high school will cut a precise hole in my metal lens boards for only (a donation of) $10.00. Definitely the way for me to go in the future.

[Peter De Smidt]

That's a great way to go, Greg!

[Jim Noel]

Only for wood or maybe plastic, but not for metal...

I have a circle cutting guide for a router, and if set up correctly, makes really nice holes in wood!!!

Steve K

The bit inthe Circle Cutter can be replaced with a metal cutting bit from Home Depot.

[Jody_S]

The bit inthe Circle Cutter can be replaced with a metal cutting bit from Home Depot.


I bought a pack of 10 1/8" shank bits for drilling and routing circuit boards (I think) off fleabay that cut aluminum like butter. I think I paid about $12 for the pack. There's a lot of CNC routers out there, so there's lots of specialised bits you can buy that also fit Dremel rotary tools.

[John Earley]

Since I'm fortunate to have a milling machine, I cut my lens boards with a boring head. Perfect holes, any size, very quickly. Before that I used a circle cutter in a drill press. Before that I used hole saws in a hand drill. Before that I used a jig saw. Before that I had someone else cut them.