Cutting 8mm 304 stainless steel

[hunter27]

Hi
I have recently bought a small R-tech 30A plasma cutter but have not really used it properly yet but now I need too cut some 8mm thick 304 stainless steel plate.
The 8" square piece I bought cost me £30 inc delivery and I have non to practice with or waste.
I need to cut it into 4 pieces and then cut a 35mm hole in the centre of each piece for a pipe to be welded in.
I am worried that if I try to use a hole saw the stainless will work harden causing me more problems.
I am planning to set the cutter on full and follow a straight edge for the straight cuts and then clamp a template over the stainless plate and cut around the inside of that for the holes.
this is from R-tech web site in the spec.

Thanks
Pete

• 8mm Genuine clean cut on mild steel, 6mm Genuine clean cut on alloy and stainless steel

• 12mm severance cut on steel

 

[madkayaker]

Good luck. Someone will know speed for holesaw and use plenty of coolent. I think plasma should be fine

 

[GrahamGKD]

I cut quite a lot of 6mm 316 and get reasonable results with my Powermax 45 - I think the quality of the cut hinges on how smoothly you keep the torch moving at the correct cut rate. Keeping a nice even movement is easy enough on straight cuts but a little more tricky on something like your holes. I would cut a suitably oversize hole in a piece of aluminum to uses as a template for the hole - probably that is what you had in mind? I would drill a hole in the middle somewhere to start the cut rather than trying to pierce it with the plasma. If you don't have any stainless to practice on do you have some similar thickness steel to get a feel for things? I never get quite as clean a cut on stainless as I do on mild steel though.

 

[hunter27]

Thanks for the replies, rather than just going ahead (as I normally do) I thought I would ask. I was planning to make a template and it's handy good to know about the cut rate as a plasma cutter is not a tool I have used before.
I would rather not drill the large hole as although I have a new Starret hole saw the right size and a slow pillar drill the hole saw blade looks a bit course for steel.
Pete

 

[Shedendman]

If you've not used a plasma cutter before then for god sake do loads of practice,your cutter is fine to cut what your wanting to do,get yourself a load of scrap any thickness's will do and have a play with it,like GKD correct torch position is a must.
You can use thin plywood as a template for the holes just cut them oversize for the torch head,check youtube you'll find loads on it there.
The starrett holesaws are mostly course looking but i find they're the best out there to use,slow speed plenty or lube guarantee a good clean hole,with a plasma you'll still end up having to clean the dross off with a grinder or file

 

[KemppiFrog]

Hi, and welcome. I drilled a heap of 50mm holes in 6mm 304 with a decent bimetal hole saws. Pillar drill on very slow and plenty of coolant. Also did some last week in 12mm 316 at 40mm. Your plasma is a bit low powered for 8mm SS. But doable. I would drill the holes and plasma the shape. And in that order. Nice boat.
KF

 

[gordon stephenson]

That's a heck of a price for the stainless. In view of that if you have not had quite a lot of practice I would forget the plasma idea, cut the plate with a thin cutting disc,and do the holes with a good quality hole saw. Get the speed right and a good pressure with plenty of cutting fluid etc. do not just let the cutter rub that will tend to harden it,

 

[waddycall]

I'd go with Gordon Stephenson's suggestion and cut the blanks out with a thin slitting disc. I recently made a rudder fitting from 6mm 316 approx 2' x 6" and cut out three pieces using slitting discs. It doesn't take long and doesn't really need any cleaning up. The edges will be square and dead straight if you're careful.

I use a 40 amp esab plasma at work. It struggles to cut 8mm mild steel, in fact I don't think it ever has - 6mm seems to be it's limit for a reasonable cut. I'd guess that a severance cut would need lots of cleaning up. As far as I know stainless needs more power than mild steel so there is no way I'd cut the parts with the esab.

It might be worth thinking about how it's being welded too. If it's being tig'd you want a good fit so if your pipe is going through the holes then hand held plasma may not be the way to go unless you spend lots of time filing/grinding to get the right fit.

Why not try the hole saw first? If you're planning on plasma cutting then there's no harm in trying the hole saw first. I have no plasma at home so if I had to make those parts and they needed to be tidy and accurate (and time wasn't an issue) I'd think about cutting the hole on the lathe with a boring bar.

 

[Hitch]

I'd be inclined to use a disc cutter, and a hole saw redgardless of what plasma it is.

 

[GrahamGKD]

Just a thought - are these parts for your boat, in which case I would have thought you should go for 316 rather than 304, unless the boat is always used on freshwater lakes?

 

[hunter27]

Right. lots of views here.
I think I will go with drilling and thin cutting disk on the first one and if that doesn't work try the plasma cutter.
The part is for my boat but it's inside. A water cooled exhaust elbow for the twin cylinder diesel engine.
They are around £200 a go so if I can make a few it will be money well spent.
Thanks for all the help.
Pete

 

[biffa]

As others have said the plasma has not got the guts, I would go for the cutting disk and then hole saw, I would opt away from the bi metal and go for a starret tct stainless steel hole saw, I know there only rated for 2mm but we use them on 8mm no problem, and we use them in hand drill, all on 316 stainless. Just take your time plenty of cutting fluid and the holes will come out much better than the plasma cut holes with less clean of required

 

[langy]

Hi
I have recently bought a small R-tech 30A plasma cutter but have not really used it properly yet but now I need too cut some 8mm thick 304 stainless steel plate.
The 8" square piece I bought cost me £30 inc delivery and I have non to practice with or waste.
I need to cut it into 4 pieces and then cut a 35mm hole in the centre of each piece for a pipe to be welded in.
I am worried that if I try to use a hole saw the stainless will work harden causing me more problems.
I am planning to set the cutter on full and follow a straight edge for the straight cuts and then clamp a template over the stainless plate and cut around the inside of that for the holes.
this is from R-tech web site in the spec.

Thanks
Pete

• 8mm Genuine clean cut on mild steel, 6mm Genuine clean cut on alloy and stainless steel

• 12mm severance cut on steel

A good plasma will cut that fine, a decent quality holesaw and plenty of cutting oil on a slow speed will get the job done.

 

[Pete.]

I drilled four 38mm holes in a 10mm piece of stainless with a tank cutter quite easily in my drill press. Clamp the work down, slow speed, drill the pilot through then do your cutting with heavy pecks of a couple of seconds each and use coolant/oil. Easy peasy lemon squeezy. Cut with grinder or hacksaw.

 

[hunter27]

Thanks for all the help. I started this morning and the plate cut and drilled much easier that I had expected being stainless steel.


Have a good Christmas and New Year
Pete