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Simple circle cutting tool for a plasma cutter


mickeyw

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I needed to plasma cut some circles today, and seeing as my freehand cutting is extremely messy I wanted to use a radius template. I had previously though of making multiple radius templates, so consulted the internet.

I know tools can be bought, but this requirement was spontaneous and far cheaper than anything I could buy.

I can't claim this idea is mine, but here is my version, and it has worked very well, and only cost me half an hour of my time, so thought I'd share.

Take one strip of 3mm steel, drill a few Ø8 (or size to suit the tip on your plasma torch) holes a regular known distance apart (1" in this case). Also drill and tap 4 M5 holes, 2 positioned 1/2" and 1" from the Ø8 hole at one end, and another 2 positioned 3/4" and 1 1/4" from the Ø8 hole at the other end. The tapped holes are the pivot positions.

This particular tool can cut from R3/4" to R7" in 1/4" increments.

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I chose to stamp some markings beside each tapped hole for easy reference.

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Take an M5 screw, grind a point on the end add a locking nut and screw into the required tapped hole.

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Centre punch your hole centre, and hopefully these pictures explain the rest.

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A little more practice and I'll get a tidier finish I'm sure.

BTW this was 1.5mm stainless. In case you are wondering, the folded box is a cover to protect my winch isolator that lives in the passenger footwell. My 3YO daughter has been using it as a step to get into her kiddie seat. Not only am I concerned about her damaging it, she might also 'kick' it on or off at the wrong moment.

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smart stuff! Have been thinking of doing such a tool for my plasma torch but never really found a solution I liked. But,thus one would fit the bill. There is one thing that has got me thinking though. How does the air from cap go pas the nozzle to cool it if the nozzle is a perfect fit in the hole? Something I missed?

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Most have air through the centre of the nozzle for cutting and between nozzle and ceramic for cooling.

Sorry, fat fingers and ipad keyboard wrote entire instead of centre, which is what i meant to write. I've amended it above. I'll look at mine later and see if it comes out between the ceramic as well - i haven't noticed before.

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smart stuff! Have been thinking of doing such a tool for my plasma torch but never really found a solution I liked. But,thus one would fit the bill. There is one thing that has got me thinking though. How does the air from cap go pas the nozzle to cool it if the nozzle is a perfect fit in the hole? Something I missed?

Not sure if I'm seeing this correctly but it looks to me like the ceramic isn't touching the jig so this would mean the cooling air would still be able to escape, although the very tip won't be cooled by this air now (the rest of the nozzle will) the tip will hopefully be kept cool by the heatsink effect of the jig in contact with it .... which in turn has the cooling air blowing on it.

The jig is a copy of a commercially available one (SWAG offroad) so if it did cause problems I guess it wouldn't be for sale still.... maybe

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Sorry, fat fingers and ipad keyboard wrote entire instead of centre, which is what i meant to write. I've amended it above. I'll look at mine later and see if it comes out between the ceramic as well - i haven't noticed before.

Which model do you have?

PS I must still be asleep as I had read it as centre anyway! :blink:

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