O/A or Plasma Torch cutting quality

[Pooh_Bear]

I have a big (21x21) square piece of 3/8 plate that I need to cut a 20 inch circle out of.
I also need 9 one inch holes drilled in it.

If I can get someone to cut this out for me with a plasma torch or O/A torch
how rough of an edge will it leave. I would like to have it smooth.

I have a 1 inch drill bit I just don't look forward to drilling all those holes.

I got another piece of steel, 4x4x.25 square tube I need a square hole cut in one end to accept a 3x3x.25 square tube cross piece.
This piece will be welded in place so it doesn't have to be as smooth.

How smooth can I expect this to be cut.
I'm thinking cut it oversize and grind it down to 20 inches diameter.
I'm hoping a torch will do a good enough job I don't need to.

So how good a cut can I get from an O/A or Plasma Torch.

Thanks.

Pooh Bear

[slowzuki]

Unless you use a machine the cut quality will be completely dependant on the operator of the cutter. A seasoned pipe fitter could chalk out the circle and bolt holes and punch them with either tool and they will be smooth and nearly perfect.

I could do it with my circle cutter but would have to grind a bit.

The plasma leaves a slight bevel on the edge so you have to grind anyways.

1" bolt holes have to be a bit oversize to accomodate any imperfections in the circle. I have burned holes as small as 3/8" but they aren't nearly as pretty.

If you need perfect holes get the drill press and oil out.

[Farwell]

Pooh Bear
If you burn the 9 holes and still have to drill or ream them to the size you need, the metal may have been hardened by the heat from the cutting process. You may be better off getting out the cutting oil and drill press. IMO
Farwell

[PineRidge]

I know a fella that has access to a CNC plasma cutter. He cut the lift arms for my grapple including the round and square holes and it all went together without a hitch. If you're interested PM me and I'll send you his phone number so you can talk with him and work out the details.

[Pooh_Bear]

The nine bolt holes are to accept one inch bolts.
I don't think I will have to be reaming any.
They just have to match the mounting plate I already have.
One center hole and holes around the outside for each angle.

A CNC plasma cutter would be great. Shipping would not.

I'll probably just go with my original idea.
Drill a hole in the center to put a bolt in.
Get some small caster wheels and mount them upside down to set the plate on.
Put the plate on the wheels using the bolt as an axle and spin it.
Use a metal lathe cut-off tool to cut my circle.
Of course I will still have to drill the holes.

School starts in two weeks.
May take it up to the vo-tech place and see what they can do for me.

Thanks.

Pooh Bear

[rswyan]

Originally Posted by Pooh_Bear

The nine bolt holes are to accept one inch bolts.
I don't think I will have to be reaming any.
They just have to match the mounting plate I already have.

Yup - that's the trick of it - getting them to match up.

When I fabbed up the index and mounting plates for my landscape rake I took the two 1/2" plates and tack-welded them together. Then I drilled the 11 holes thru both of them at the same time - one 2" hole for the pivot pin and ten 7/8" holes for the hitch pins I was going to use to set and hold the rake angle.

[dfkrug]

Bear, a plasma cutter will do both jobs quite well, if the operator
uses a guide. The straight cut can be done with no bevel if the
tip is in good shape, and the lip of slag knocks off easily. I use
my TD Cutmaster 51 for holes too, as I hate drilling them. I made
hole templates out of 1/4" aluminum and drill a pilot hole. These
holes can be good enough for bolts, but not machined quality. When
I need machined quality (as for a pivot pin), I cut an extra big hole and
weld in a bushing. I have had the PC for more than a year now and
I am amazed what I can do with it. 1/2" steel cutting is slow, but
sure beats the other methods.

[deerhunterf350]

I currently have a O/A setup, and a lifetime lease on Tanks, with no demerge ( no preset timeframe that the tanks must be exchanged every X months or a penalty is accessed)

The Last exchange was 05/05 , I don't remeber the exact amount, but Actetlyne was like 60.00 ,and Oxeygen was 50.00 . I am sure the costs have only went up.

Questions are.

What is the Consumable cost on a Plasma cutting setup? ( Tips , GAS, ect.)

What Size Tanks and cost for Gas.

Does it use similar amounts of GAS like the O/A setup uses O when blowing through steel.

Does Plasma cut rusty, scaley steel very weel?
O/A tends to pop a little but after the work gets hot , it doesn't pop that much.

[Highbeam]

No gas for plasma cutting, only compressed air and electricity. Consumables are quite cheap so long as you use the standard ones. It is cheaper to run plasma cutters than o/a but the negatives are that you need power and air, and you can't heat stuff up to bend it. Initial cost can be quite high for a plasma setup.

[dfkrug]

Yes, no gas, no bottles. Initial cost is high as stated. $1500+ for 40A name
brand. Less that $1000 no-brand from HF tools. I bought a lot of
consummables with my PC, and I have hardly used any of them in
1.5 y. I use it about every other week. Hard to say what kind of
hours. I bought a fancy straight cutting guide, but then I find just
a 1/4" thick straight edge wks very well.