Looking for Ideas - Cutting Lexan Disks

I'm trying to come up with a way to easily cut out disks of Lexan to a given diameter.

A fly cutter would be ideal...but I don't want the center hole that a fly cutter normally produces. I want to end up with an unblemished disk of clear plastic. This isn't a standard size, so a hole saw won't work. And since the disks are to fit existing holders, a reasonable amount of precision is needed.

The only thing that comes to mind is to clamp down the plastic and use the fly cutter without the pilot drill. Any other ideas?

Ron Wanttaja

Sounds like you need to modify a hole cutter, which is an arm that comes off a center drill that has two adjustable cutting blade.

The modification is to shorten the center drill to where is it below the cutting edge of the blades. Put a thin sheet of plywood or something on top of the piece you want, clamp it with the plexiglass, and go to town.

https://www.amazon.com/Adjustable-Ho...s_id=256292011

[edit]

Sorry, you mentioned "fly cutter" which is probably the same thing I'm thinking of.

Frank "Why are all your tools ground down?" Giger

Maybe a 3" (or whatever size) disc of 3/4" wood with a pilot hole half inch deep but not all the way through. The disk would fit in a scrap of plywood with a three inch hole.

Band saw?

Holesaw without the pilot bit.

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Originally Posted by Frank Giger

Sounds like you need to modify a hole cutter, which is an arm that comes off a center drill that has two adjustable cutting blade.

[edit]

Sorry, you mentioned "fly cutter" which is probably the same thing I'm thinking of.

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Yes, close, but yours at least has two arms. This is what I have:
Attachment 8869

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Originally Posted by FlyingRon

Holesaw without the pilot bit.

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Yes, but hole saws come in specific sizes, and I need something that'll be between the sizes. Their sizes are also the OUTSIDE diameter, and I'd actually be needing a specific inside diameter. Though I'll have to look at my 3" hole saw, the ID might be close.

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Originally Posted by Dana

Band saw?

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Part of the problem is that I will probably want to produce several of these, and am hoping to reduce the amount of cutting and filing to fit.

The thread on the P-51 panel got me to thinking about building simulated instruments for a similar replica panel. I used Solidworks to design the instrument bezel, fitting into a standard hole and designed to take a piece of glass/plexiglass/lexan. The problem is, the lip is only about 0.1" wide. Since the simulated instrument has to fit into a standard hole, changing the size to match available tooling isn't really an option.
Attachment 8870
So I'd love to be able to use a standard setup and crank out a number of these. Once I get the front bezel settled, I'll start working on the back half of the instrument, to include the face and the needle.
Attachment 8871

Ron Wanttaja

How about a laminate bit in a router? Use other tools to make a template disc out of Al or plywood and duplicate it in plexi using the laminate bit. Carpet tape could attach the plexi blank to the template.

I worked at a ski boot factory 41 years ago. We would stamp out shapes that resembled a bowtie from 4x8 sheets of lexan. Our lexan was .125 thick. The cutter was thin tool steel with a knife edge along one long edge. These thin lengths of tool steel were embedded in a slot machined in a thick wood base plate. Think of a giant cookie cutter. We had a big hydraulic press but you might could use an arbor press to make a few if your stock is thin enough.

Should work with no pilot in the drill press if you go real slow and clamped tight.

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Originally Posted by Jeff Point

How about a laminate bit in a router? Use other tools to make a template disc out of Al or plywood and duplicate it in plexi using the laminate bit. Carpet tape could attach the plexi blank to the template.

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That's a very good thought. Using the router didn't occur to me, probably because they scare the bejesus out of me. But that would certainly work, and I have several types of laminate bits.

This is where Solidworks and a 3D printer come in handy. I can draw up and print the pattern for the laminate bit, including any handling aids needed (like a countersunk hole dead center for a bolt).

Ron Wanttaja

Ron: Much easier this way...: https://www.usplastic.com/catalog/it...0806&catid=441

or: https://www.amazon.com/MEYA-20pcs-Ac...654244&sr=8-13

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Originally Posted by CraigCantwell

Ron: Much easier this way...: https://www.usplastic.com/catalog/it...0806&catid=441

or: https://www.amazon.com/MEYA-20pcs-Ac...654244&sr=8-13

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Ha! Might be worth it. Cost isn't that bad, especially the ones on Amazon.

I thought it was too big (my glass specs at about 2.9"), but it made me think about my design. I'd completely forgotten the instrument hole is 3 1/8"; I need to enlarge my design slightly, at which point an even 3" diameter glass disk would probably be right.

I need to rework the design anyway, some instruments are installed from the pilot side of the panel, and my outline is wrong for that.

Ron Wanttaja

Remember that a 3" holesaw will cut a disk about 2.875" diameter, allowing for a 1/16" kerf, there's your 2.9".

There are also 3-blade adjustable holesaws that might work better without a pilot than a 1- or 2-blade flycutter. I have an old Craftsman one but they're still made today by other companies.

The pre-cut disks look reasonably priced, but since you're rolling your own bezels via 3d print, why not design the bezel to take a square lens? Or find a community college nearby with a tech lab, or a 'maker space', and use their LASER to cut your own discs?

1/16" Lexan can be cut easily with sheet metal snips if you want it quickly by hand.

Thanks much for the advice. If I were building a 4" instrument, I'd probably use a router. But I bought the Amazon 3" disks, because if I build any more instruments, most are probably going to be three inches.

A quick slap-together of the final product. It's not actually bolted to this old Warwick Bantam instrument panel, so it's not lined up.
Attachment 8873
Instrument face is just printed on plain paper with a standard ink-jet. I have a small sublimation printer that'll put some gloss on it; may give it a shot.

Learned quite a bit on this one, will come in useful if I end up making any more.

Ron Wanttaja

Didn't know the Bantam was that fast....:rollseyes:

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Originally Posted by CraigCantwell

Ron: Much easier this way...: https://www.usplastic.com/catalog/it...0806&catid=441

or: https://www.amazon.com/MEYA-20pcs-Ac...654244&sr=8-13

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If you have access to a lathe, make 2 wood templates to actual size. Clamp oversize Lexan between wood templates in headstock and tailstock and turn lexan to size.

Bob
WB8NQW

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Originally Posted by CraigCantwell

Didn't know the Bantam was that fast....:rollseyes:

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Of course! "Bantam" is an anagram for "Batman", you know.... :-)

Actually, my model was a P-51 airspeed.

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Originally Posted by Bob Willman

If you have access to a lathe, make 2 wood templates to actual size. Clamp oversize Lexan between wood templates in headstock and tailstock and turn lexan to size.

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That's an interesting idea. I guess one could use carpet tape to really tie down the Lexan. I may give it a try, if only as an excuse to run my lathe.

Ron Wanttaja

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Originally Posted by rwanttaja

I'm trying to come up with a way to easily cut out disks of Lexan to a given diameter.

Any other ideas?

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Stack them in a lathe between centers and turn them. I have done this before and it works very well, the OD can be turned to +/- .005" without too much effort.

I've been using a CNC router for a few years for my Hatz build. I have cut plexiglass, wood and now aluminum. Depending on the max size you want to cut, a small 12"x24" CNC router will cost less than $500. It's my most versatile tool. Some projects:

Attachment 8874

Wood nose pieces for the wings.

Attachment 8875

Elevator trim handle cut from 1/8" aluminum

Attachment 8876

Elevator trim built from aluminum

Attachment 8877

Face plate for elevator trim cut from plexiglass.

Attachment 8878

Throttle quadrant made from aluminum.

My WebFu is weak, sir, so if you could tell me which machine you got I'd be much obliged.

I bought mine a few years ago from Amazon. It's not listed anymore. There are plenty of other CNC routers listed on Amazon.

https://www.amazon.com/s?k=3040+cnc+...f=nb_sb_noss_1

You will need some computer skills as the parts are all designed on a computer.

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Originally Posted by rwanttaja

I'm trying to come up with a way to easily cut out disks of Lexan to a given diameter.

A fly cutter would be ideal...but I don't want the center hole that a fly cutter normally produces. I want to end up with an unblemished disk of clear plastic. This isn't a standard size, so a hole saw won't work. And since the disks are to fit existing holders, a reasonable amount of precision is needed.

The only thing that comes to mind is to clamp down the plastic and use the fly cutter without the pilot drill. Any other ideas?

Ron Wanttaja

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Why cut. Lexan has a low temp threshold. Make a correct diameter ring slightly over size and heat metal ring with torch to melt the disc. ring will need a handle, good idea to use a small diameter handle that can be chucked in a drill press. Not rotating but use the handles to press the heated "branding iron" down with equal force.

Used to work with plastics, when we worked with lexan, 150 deg F for 8-hours to remove excess moisture then we would very quickly bend or put on vacuum table.

Best regards,
Mike Bauer

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Originally Posted by rwanttaja

I'm trying to come up with a way to easily cut out disks of Lexan to a given diameter.

Ron Wanttaja

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CNC: I do this all the time.
Attachment 8881
My 6040 (~18"x24") was about $1000 and is a brilliant tool for SO many things.
-Christian von Delius

CNC routers and 3D printers work for more than building parts. If you look closely at my elevator trim picture in my post above, the ball screw mechanism is a part from a 3D printer.

So what was the ultimate solution?

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Originally Posted by Frank Giger

So what was the ultimate solution?

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I bought the 20-piece set on Amazon for $15. Now I have to come up with something to do with the remaining 17. Could make some really ugly goggles, I suppose.

Really appreciate the range of suggestions, here. Intrigued with the concept of using a CNC router. If I could come up with MORE things to use it for, I might buy one.

Ron Wanttaja