Cutting circles in thick plate.

[markcantweld]

Does anyone have any tips on cutting circles in 10mm mild steel plate?

I want to cut, 2 4" circles.

I don't have a plasma cutter unfortunately.

All I have is a grinder, hand drill and saws.

All I can think so far is drilling gazillions of holes and then tidying up. But that will take forever!

Thanks!

 

[MattF]

If you have access to a drill press, a tank cutter with the pilot/centre bit removed?

 

[jimmyspeed]

i used a starrett tct hole saw to cut some several 30mm holes for an exhaust manifold, they cut quick, but need cleaning out regularly.

Definetly a job for a drill press.


the only problem you might have is cost i can image one that size being pricy!

not what i used but might work

http://www.starrett.co.uk/shop/holesaws/dual_pitch_professional_bi_metal_hole_saw/

 

[chevy2]

That'll have to be a stout drill press to do 4" holes in 10mm plate,
I'd be more inclined to leave the pilot drill in the holesaw and weld the hole up afterwards if you're going down this route,

for only two discs with the equipment you probably have is rough cut the discs using an angle grinder with 1mm cutting discs slightly oversize to a kind of 50p shape and then finish the outside round with flap discs.

 

[markcantweld]

Thank you for the replies.

I can get the use of a drill press at work (when no-one is looking!) but I don't think we have hole saws that big. I'd never seen a tank cutter before. Interesting, I'm not sure how slow our drill goes but could be an option.

I had a look at Starret and then fell over. I can't afford that for little used tools! I like the 50p idea.

 

[chevy2]

If you havn't got any holesaws you'll need to factor in another £15-20? for the arbor to screw the holesaw onto?
can you justify the cost to make only two discs?
you'll still get through a few cutting and sanding discs on that 10mm plate though.

 

[hotrodder]

If you decide to go the holesaw route then drilling 2 or 3 holes on the waste side (breaking into the holesaw cut line) will make life easier by giving the swarf an escape route. If i want the disc rather than the hole then i knock a hole through a piece of wood first and use that to guide the holesaw until it's cut a groove deep enough to follow without a pilot

 

[astro_al]

Not sure if you want the discs or the sheet with holes in.

If its the discs, just buy them in.

4" discs cost peanuts. If you cant find 10mm, buy a couple of 5 mm and weld em up.

Better yet, get a machinist to chop you off two slices of 4" bar & face it up, if necessary (depends on their facilities how they do it).

Chain drilling sucks.

Al.

 

[markcantweld]

Its not the discs I'm after. It's the hole. It doesn't have to be overly tidy either. It's only a flue outlet.

 

[astro_al]

Find someone local with a plasma cutter.

Al.

 

[bigbadbugga]

This is just an idea, to throw in there.

I have a router. I also have a selection of carbide burrs. I can make a template for the router to follow. 20 x 0.5mm cuts might be doable?

 

[chevy2]

This is just an idea, to throw in there.

I have a router. I also have a selection of carbide burrs. I can make a template for the router to follow. 20 x 0.5mm cuts might be doable?

Thats a hell of a lot from a router in 10mm steel and the carbide burrs also,
can you not find anybody with oxy/acetylene cutting gear as to cut the two holes out would only take a few minutes to do?

 

[markcantweld]

Well, I have given up trying to do it myself. I don't think I can safely do it with the tools I have, and don't fancy spending a fortune just yet.

My dad has taken over, I think he has access to a plasma cutter.