advice sought - what cutting bit material for cutting thin stainless steel sheet?

Hello

"tungsten carbide or diamond grit coated or carborundum?"

I need to cut a couple of circular holes (150mm dia) in some 0.5mm thick "304" grade stainless steel sheet which has been formed into a curved shape and polished (which I think means it has likely been work hardened).

I have decided upon a Dremel type of tool, perhaps with some lubricant on the work piece, and adjustable speed. I think a grinding type of bit, e.g. a 3mm cylindrical "burr", will suit. This is the sort of bit shape I hope to try:

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or

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I can buy them made from tungsten carbide, or diamond grit coated, or the "carborundum" type of grinding stone.

Which is likely to be best? I can see that the cost of any of the types if affordable for me and I don't need to make hundreds of cuts - I want to use which is going to give me the least heating distortion and is likely to be the fastest to cut.

Thanks for any advice on which type to choose!

DDS

Reply to
Duncan DiSaudelli
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The problem I always have with burrs and grindstones is keeping them on track.

All 18-8 stainless steels are buggers for finishing with hand-held tools. The curved shape implies some work hardening, but the original sheet will have already been work hardened by rolling. The benefit from the shaping means that it will be much stiffer than a flat sheet, hence on balance easier to work.

If it was thicker, I think I might rough them out with a slitting disk in a 125 mm angle grinder. At 0.5 mm, I'd be inclined to start by using a Dremel with the fibre-reinforced slitting disk, without lubricant. The disks won't last all that long. I say no lubricant because of the difficulty of maintaining supply. You will get the fastest cut using the thin, brittle, non-reinforced disks but they will break if you apply any out-of-plane load.

One you have roughed out the cut, I would use a cylindrical abrasive bit. The ones which fit a dremel will be rather small for cleaning up a peripheral length of half a metre. You would be better off with a die grinder, and abrasive bits perhaps 25 mm diameter.

You might be able to do the stage between Dremel "rough cut" and Dremel "final finish" using a standard grinding disk on a 125 mm angle grinder. Much faster metal removal. Some care needed!

0.5 mm is *probably* just too thick to use a shears. You can get "Gilbow" type shears with curved blades to help making curved rather than straight cuts.

IIRC this "universal" type will also cut curves, at a price!

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Might be worth checking if you happen to have a normal (straight) shears.

Reply to
newshound

Hello newshound

You've made some good points and your mentioning of "die grinder" has shown me that this might be a better purchase than a dremel. I can see some very affordable ones, and the bits for them are likely to be heavier duty. I remember coming across the term before but I didn't know what it meant. Now I can see it might suit me very nicely.

My plan is to fix the rotary tool (of whichever type I buy) to a bench and then, by hand, introduce to the bit and then rotate the work piece about its axis, in order to be able to control the feed rate. The axle can be bolted to the same bench and I am confident that I will be able to form a nice circle.

I think a die grinder with suitable clamping should work very well, and thanks for the advice. I shall look into the cutting disks you mentioned & I'll see what types of other cutting bits are available (I still think a burr approach might well suit this particular task).

Thanks

DDS

Reply to
Duncan DiSaudelli

Maybe something like this?

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Reply to
dennis

This is the best solution by far.

Reply to
F Murtz

dennis, F Murtz - I didn't realise that that sort of "nibbler" would be as affordable. I will see if it would work for my particular set of circumstances. Thanks for the suggestion and recommendation.

DDS

Reply to
Duncan DiSaudelli

TC. Diamond coated die grinder bits too often have less fine diamond dust than a moth, and it comes off almost as easily.

I wouldn't nibble a curved surface, you'll get too much distortion.

NT

Reply to
tabbypurr

I had one of them (from Machine Mart). The "bit" broke after rather limited use and I couldn't get a replacement. They are certainly good on steel or aluminium and should work on 0.5 stainless, but as I said before it is a really difficult material to work with in this way.

Reply to
newshound

Distortion: that's a good point. Thank you for the advice NT. I'll try TC bits in a die grinder, and I will fix the grinder and rotate the work-piece in order to do the circle. I can drill an entry hole and then introduce the burr bit, and rotate slowly.

Thanks all for your help and suggestions.

DDS

Reply to
Duncan DiSaudelli

It may be worth considering for roughing out, though. You will be able to see how far the distortion extends from the cut, and (depending on the application) it may be possible to re-form the edges to the original profile.

Reply to
newshound

I have one of those. Pretty aggressive for precision work and you obviously need a supply of compressed air.

Reply to
Tim Lamb

I have some air shears, they are aggressive. I had a hand operated punch that worked well, its has gone somewhere but I don't know where.

Reply to
dennis

You can get hand operated nibblers too. Preferably one where you can buy new jaws easily if cutting SS.

I've got a rather rare electric version - made by Hitachi. Does tend to run away with you. ;-)

Reply to
Dave Plowman (News)

Plasma cutter?

Reply to
Fredxxx

To avoid the need for compressed air couldn't you use an electric drill nibbler attachment? eg:

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Alan

Reply to
Alan Dawes

In article , Duncan DiSaudelli scribeth thus

Had a go using some air power tools in a garage a while ago, that above seems like a very good investment:)

Reply to
tony sayer

In message , tony sayer writes

You'll end up with a shed floor covered in tiny 1/8th. Moon chips:-)

Reply to
Tim Lamb

Probably a bit fiddly compared with a purpose-built tool, whether manual or powered.

There are two sorts of devices described as nibbler

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The "shears" type is OK for making a linear cut, the punch and die type which takes out a little rectangle at a time is best if you are cutting out "features" like a square recess or a T-feature.

Reply to
newshound

In message , newshound writes

Anyone still have their Gosscut metal shears?

Reply to
Tim Lamb

In article , Tim Lamb scribeth thus

Reply to
tony sayer

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