Cutting a 4" circle....

[CGCINC]

I need to cut several 4" circles so that 4" PVC will fit loosely in them.

Is it possible to use a small cut off piece of the PVC and basically trace around the PVC with the plasma cutter while cutting the hole?
Yess, I can freehand it but I would like it to look a little better than freehand and I don't want to do a lot of work after the cut.

[posixPilot]

Seems like it would work, but the PVC might get a bit melty and make a mess. The offset from the torch would be pretty large too ... I think you would end up with at least a 5" hole. You might want to try a 3" pipe to make the size a bit closer.

Cheers
Mike

[NRM]

2x what posixPilot said. I think a tuna can might work pretty well also.

[KSmith]

I need to cut several 4" circles so that 4" PVC will fit loosely in them.

Is it possible to use a small cut off piece of the PVC and basically trace around the PVC with the plasma cutter while cutting the hole?
Yess, I can freehand it but I would like it to look a little better than freehand and I don't want to do a lot of work after the cut.

A good chance to try your bandsaw in vertical position, and cut a disc out of wood the right diameter. Can allow for the lesser dimension due to the torch cone. Draw your plasma around that. If you put a short broom handle-like handle on it, would help get your pattern holding hand out of the way of the torch.

ken

[undercut]

A good chance to try your bandsaw in vertical position, and cut a disc out of wood the right diameter. Can allow for the lesser dimension due to the torch cone. Draw your plasma around that. If you put a short broom handle-like handle on it, would help get your pattern holding hand out of the way of the torch.

ken

I like your idea about the broomstick. CGCINC will need to ensure all fleshy bits are well away from the cutting arc. The circle is going to be quite small. Probably won't be able to cut the circle in one go if the blade is wide but sure if you take a few swipes at it.

[Rambozo]

I don't know about a plasma, but with a cutting torch, I've often used a piece of string or wire with a loop tied in one end to guide around a circle. Infinitely adjustable and just secure the other end to the center with a drilled hole or a tacked on post. Nothing to block your progress, one quick pass and you're done. Cheap, easy and fast circle cutter. I can't freehand anything worth a damn.

[everlastsupport]

I don't know about a plasma, but with a cutting torch, I've often used a piece of string or wire with a loop tied in one end to guide around a circle. Infinitely adjustable and just secure the other end to the center with a drilled hole or a tacked on post. Nothing to block your progress, one quick pass and you're done. Cheap, easy and fast circle cutter. I can't freehand anything worth a damn.

Rambozo is right, this method is simple works quite well on about everything but expanded metal.

This is something quick and dirty I made and it worked quite well (but you need a magnet; maybe $2 at Hf and it came with two of them).

http://www.everlastgenerators.com/fo...ghlight=magnet

Then later bought this setup.

http://www.everlastgenerators.com/fo...t=plasmahelper

Waiting on Rod to chime in here with his 5HP 4 stroke plasma circle cutter. Kidding Rod

[SeanMurphy265]

You could also make your own circle cutter with some shaft collars. Get one collar that will fit your plasma torch. Weld a piece of 3/8" round bar to the collar that fits the plasma torch. Get a 3/8" collar and weld a 1/8" piece of round stock to it so it will be your center point. The 3/8" collar will slide up and down the 3/8" round stock making it adjustable. It would probably cost you $10.00 to make, and you would have an adjustable hole cutter.

Swagg Offroad has one that's not to pricey.

[Titan winch]

You could also get something like this and add a threaded rod with a sliding anchor point to it. I find this makes any tupe of circular motion a breeze as you can loosen the outer ring and this allows turning much easier compared to a stationary stand-off
Cheers

[CGCINC]

All great ideas!

I bought a 3" coupling to try it but it was going to be too small so I ended up just free handing it.
Works for what I'm doing right now but I like the adjustable collar idea that Seanmurphy265 had!

Thanks everyone, you soon will see my Amazing free hand abilities!!! lol