Cutting small, perfect circles?

The Olfa compass cutter goes down to 1cm diameter. But if it's too small for a compass cutter, you have to make a punch. Find some metal tube of the right diameter and sharpen one edge - voila, a punch!. If no tube is exactly right, get the nearest undersize and expand the end using a cone of some sort (not ice-cream, of course). What are you cutting - polystyrene, paper, or something tougher?

What are you punching? Paper, film decals? How many holes or discs you need punched out?

If it's thin stuff and you only need a couple of cycles I was thinking you might fashion your own punch with a piece of metal and a dowel. Sharpen one edge of the metal strip, wrap it around the dowel so that the sharp edge forms an overhang. Secure it with glue and/or tape or maybe a auto hose clamp.

You will have a little nib in your disc (careful on the typos here) caused by any gap between the ends of the metal but nothing that shouldn't clean up.

I cooked this idea up sometime ago when I ran into a similar problem but I never tried it out so I have no idea if it will even come close to working. It seems like it would though, depending on how well you can work that metal strip into a cutting blade.

WmB

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Probably a lot safer to form and assemble the cylinder FIRST and sharpen the edge LAST with a grinding wheel. Always try to finish with the same number of fingers you started. No fewer and no more. ;-)

WmB

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Thanks for the quick answers. I am cutting thin styrene. I'll take a look at the Olfa solution (since a Michael's is down the road), but then go pipe hunting.

Let us know how it turns out. A little heat to your punch might be your friend too. Not hot enough to melt, but just enough to help soften the styrene.

WmB

To reply, get the HECK out of there snipped-for-privacy@earthlink.net

If you're cutting plastic, try a circle template from an art store, Use a needle in a pin vice to gradually score a cut. This works but requires a little edge clean up after. For clean edges, try a lathe or possibly chucking a roughly shaped sheet in a minidrill and using a blade or pin as a cutter. Chek

If the plastic is fairly thin, then I think a *quality* bow-compass should suffice. One with two points (a.k.a. "divider(s)"). For more control, hold the "divider" still, and at a slight angle, and rotate the *plastic* beneath the divider.

One source I would never had thought to look at was in a scrapbook store that carried all sorts of art supplies. There are a number of punches made for fancy paper work that can be used. I picked up three for about $2-3 each and now have punches that produce 1/2" and 3/4" inch circles as well as the cast 5-point "fat" star used on T-28s and T-35s.

Can't hurt to look!

Cookie Sewell

Hobbico makes the tool you need. It's a "Circle Cutter" p/n HCAR0230 $6.69 ea. Cuts paper, film, leather, vinyl, fabric, plastics, rubber, and more. Circles cut from 10mm-150mm (as in .39"-5.9"). Your dime is 17mm. The tool comes with spare blades but extra are $4 pkg. Mine came in my shop (for my R/C car repair shop) today and I'm using it to cut ventilation holes in nitro R/C bodies that are typically .03" thick lexan or polycarbonate plastics.

Dave

you can use spent brass. as in guns. if you have a friend that reloads, then ask for some of his. otherwise hit a local gun show. make sure the primer is spent first, for safety.put the plastic on a piece of pine, use a hammer to strike the circle. you can also sharpen the brass with xacto blade to make a finer cut.

jack

I solved my own problem. As I suspected, using a compass that is over

7 inches tall to scribe/cut out a perfect circle slightly large than 1/4" is tricky--it is way too easy with a 7 " lever arm to flip the compass or "walk" it across the styrene.

So, I stuck the needle po>>

Mark Wilson

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"If we lose the war in the air, we lose the war, and we lose it quickly."

--Field Marshal Bernard Montgomery

RAAM FAQ:

Thanks--that's what I ended up doing, and thinking I had discovered something new...;)

Mark Wilson

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"If we lose the war in the air, we lose the war, and we lose it quickly."

--Field Marshal Bernard Montgomery

RAAM FAQ:

You can get a set of wad punches from an engineering supply shop ,they start at 3/16 " and usually go up to 5/8" or 3/4" , maybe you can buy them individually also they are generally used for cutting gaskets etc . I have a set of Blue Point wadd punches sold by Snap-On they come in a plastic case and the interchangeable cutting edges screw on to a mandrel ,it even has a spring loaded centre pin for locating the centre of the circle you want to cut out. Can't remember the cost but they will last a lifetime

Just need end grain hard wood or a block of lead to use as cutting surface .

My memory was jolted by your reply ,I remembered my compass cutter hiding at the back of the drawer in my hobby desk . Made by DAFA comes with spare baldes and leads for drawing as well as cutting .

10mm-150mm circles ,even has a little plastic centering thingy to put the centre pin in so you don't poke a hole thru the centre of the circle you cut out .

Thanks for the memory recall

Any halfway-equipped chemical lab stockroom or supplier should have cork borers. These come in various sizes, usually nested as a set. For this kind of quantity, I'd just try to make friends with the local high school chemistry teacher or anyone you know who works in a lab and ask for a favor.

-- C.R. Krieger (Been there; bored that)

Templates are for drawing not cutting. You could draw the circle on aluminum, etc. and then after you cut it you'd have a usable master. Or you could get the appropriate drill and make your hole in an appropriate metal. hth

The Keeper (of too much crap!)

That's not quite true. I use a template and a dentist's probe (the sharp needle-like one) for cutting small circles and it works pretty well.

The hard part is keeping it from moving while scribing the circle.

Cookie Sewell

On one project I wanted some circular ribs out of thin plastic. I used scotch two faced tape to attach the plastic sheet to a piece of flat wood, and then cut the two diameter circles through the plastic slightly into the wood using my drill press and a variable size circle cutter. You can clamp the wood to the drill press plate or use a vise to hold the wood. I actually cut multipe pieces glued to the same board. Then carefully pealed the part off the wood and cleaned it. The tape was the Scotch stuff. Basically brown paper with adhesive attached. You press the adhesive side to the wood - peel off the paper and are left with an adhesive surface to attach the plastic. The tape is in a standard size roll so you have to lay strips next to each other. I believe they also make sheets of the stuff - but some of these products have become hard to find as glue up artwork has been replaced with computer graphics. I doubt the thicker stuff that has a backing with adhesives on both sides would work - bot a rigid enough mount. In this case I wanted it to look like aircraft structure - so i also drilled the lightening holes while still on the wood.

Val Kraut

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