Need circle cutting guide for plasma cutter

I have a friend that uses tubing 'bout a 1/4" thick with a clamp flange welded to it. Put it on the metal, clamp in place and use the inside as a guide. R. Wink

. >What do you folks use for a circle cutting guide with your handheld

Second hand speaker magnet with a bolt glued on the back, and a bagful of 1/2" strip with 10mm holes drilled at different distances to take the nozzle

Works well on aluminum?

;)

Joel. phx

On 22 Sep 2004 10:22:16 -0700, snipped-for-privacy@yahoo.com (Ronnie Lyons, Meridian, Idaho) calmly ranted:

SWAG: Cut some masonite, etc. boards for your circles. Drill the center and use hole saws to cut them out. Save the holes. (If you have to use a router for odd-sized holes, you can always rout the specific size hole you need after drilling the center. Match that to the new panel for chalking the cutline.

Then make steel templates from these, lest they catch fire.

Determine the offset for the cutting head and go from there.

The baby Hypertherm won't cut aluminium as cleanly as steel, so you can just do it by line following. We don't have TIG, just MIG, so are mainly cutting steel anyway.

Besides which, a speaker magnet will stick to aluminium sheet quite happily - just put a piece of steel plate on the back, and don't expect to be able to hang from it

BTW - anyone (else) cutting Ti with a plasma cutter ?

What do you hook the end of the string too...magnet?

Using string or wire works OK, especially on thin material. I have a whole box of junk I call circle cutters. The most basic cobbles are a piece of 1/16 X 1 steel, with an 1/8 hole in one end, and a nozzle sized hole at the arc radius. A cleco can be used for a quick pivot, or use a machine screw. Just drill new 1/8 holes for each radius. One step up, substitute a piece of readi rod for the strap, use various nuts for adjustability. A major improvement when cutting thicker material is a socket for the nozzle, to hold it square. One quickie I made for larger circles holds the barrel of the torch instead of the nozzle itself. With all of them, I've found that the most important thing is that there be minimal friction, so that the tool swings smoothly in order to get a steady cutting speed. It's harder than it sounds, partly because the torch hose always finds a way to hang up on something part way through the circle. Which reminds me of an old joke - contractor shows up to board an airliner, has hundreds of feet of extension cord draped from his shoulders. Stewardess asks why, and he says "because if I have to get out quickly, I know that f*%&king cord will hang up on something for sure". :-)

Wayne