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Author Topic: Advice Needed: Cutting Circles from Thick Plastic  (Read 458 times)
R. K. Beetle
Deck Hand
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United States United States



« on: May 19, 2017, 02:22:23 pm »

Does anyone have a good way to cut circles out of thick plastic? When I say "circles", I mean I want to keep the circular part (like for goggles, viewing ports, etc), not I want to make a circular hole. When I say "thick plastic" I mean something you can't easily cut with a utility knife or Exacto blade, like Lexan or Perspex.

My go-to method, so far, has been to use a hole saw in my drill press and remove the center drill bit. One problem with this is that the plastic circle disconnects from the waste before the saw has gone all the way through, so I'm left with a thin, ragged flange around the circle (usually melted into the saw teeth). The bigger problem is that the circle starts spinning, and presses against the surface below, leaving scratches.

How do others do this?
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SeVeNeVeS
Immortal
**
England England



« Reply #1 on: May 19, 2017, 02:37:28 pm »

Off the top of my head.....

You could be half way there. Slower speed on the drill could stop the melting, cut to almost through, then use a sharp knife to finish cutting, clean any ragged edge with a file or sandpaper, a sacrificial soft material underneath may stop scratching, if you don't cut right through, hopefully no spinning will happen.

Good luck, do let us know how you get on with updates.

Eddit.......Wrap it in cling film first?, if it does spin or move, no scratches , dunno, experiment all part of the fun  Grin
« Last Edit: May 19, 2017, 02:47:47 pm by SeVeNeVeS » Logged

Hektor Plasm
Zeppelin Captain
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United Kingdom United Kingdom


All-Round Oddfellow.


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« Reply #2 on: May 19, 2017, 06:44:27 pm »

I have cut circles out of, and in thick plastic and thin wood with the old 'two nails in a stick' method- one nail in a length of wood for a pivot, that goes in the centre of the circle, and the other in the wood at the desired radius. Give this one a quick sharpen with a file and begin the long trepanning job...

It does take a little while, but the edges are very nice. If you don't want a hole in the middle of the disk, perhaps fit the pivot with a sucker from a shower hook?

HP
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Synistor 303
Gunner
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Australia Australia


Zenyna Ironbracker


« Reply #3 on: May 20, 2017, 05:43:37 am »

I have used a tile cutting hand saw. You know, the type with a metal cutting 'string' on a saw frame. It is fairly fast, and the edges are good, but you have to be precise about cutting in a circle.

Cheers
Rob
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RJBowman
Zeppelin Captain
*****


« Reply #4 on: May 20, 2017, 07:49:45 am »

Rough cut with saw or router or dremel. Sand edges.
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Justin Time
Officer
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United States United States



« Reply #5 on: May 20, 2017, 08:24:11 am »

Since you have access to a drill press, have you tried one of these? http://www.acehardware.com/product/index.jsp?productId=1292919&KPID=982971&cid=CAPLA:G:Shopping_-_Wood_Products&pla=pla_982971&k_clickid=ccbb1e45-2bd0-4779-9d7a-cbe8674142d5  (not affiliated, just a Google result  Grin)

I used one of these (well, wore out several) for cutting circles.

They are adjustable and you can get them up to about 12" wide.  They are really for cutting holes, but if you flip the blade around and remove the center but, you can get disks  Smiley

JIT
« Last Edit: May 20, 2017, 08:28:28 am by Justin Time » Logged

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Justin Time
Officer
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United States United States



« Reply #6 on: May 20, 2017, 08:33:24 am »

I also just remembered this: http://www.delviesplastics.com/p/Laser_Cut_Clear_Acrylic_Discs.html From 1" to 16" diameter and 1/16", 1/8" and 1/4" available.

JIT
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RJBowman
Zeppelin Captain
*****


« Reply #7 on: May 20, 2017, 04:44:06 pm »

I also just remembered this: http://www.delviesplastics.com/p/Laser_Cut_Clear_Acrylic_Discs.html From 1" to 16" diameter and 1/16", 1/8" and 1/4" available.

JIT



A great find, but i don't know what I'd do with 50 of them.
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R. K. Beetle
Deck Hand
*
United States United States



« Reply #8 on: May 21, 2017, 12:24:21 am »

Since you have access to a drill press, have you tried one of these? http://www.acehardware.com/product/index.jsp?productId=1292919&KPID=982971&cid=CAPLA:G:Shopping_-_Wood_Products&pla=pla_982971&k_clickid=ccbb1e45-2bd0-4779-9d7a-cbe8674142d5  (not affiliated, just a Google result  Grin)

I used one of these (well, wore out several) for cutting circles.

They are adjustable and you can get them up to about 12" wide.  They are really for cutting holes, but if you flip the blade around and remove the center but, you can get disks  Smiley

JIT


That is a great idea. I'll pick one up when I next need to cut out a plastic disk.
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