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Old 03-08-2020, 01:23 PM   #21
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If you do this by hand, use a drill with a clutch to prevent jamming. As someone said, when the bit binds, it will break your wrist. We have a big Dewalt at work and at the first sign of binding.....it cuts out. Its a great safety feature.
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Old 03-08-2020, 03:30 PM   #22
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306 is pretty soft and 316 is much harder, the chips from a hole saw with 316 are very small and clean. 306 gums up the teeth on the can. A side handle on your drill is a must if you are going to use a hand drill with a hole saw.

My fabricator used a mag drill, which magnetically holds the drill in place. A piece of ferrous steel under the stainless project will allow the magnetic drill to lock in place.
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Old 03-08-2020, 04:21 PM   #23
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For some reason people think SS is hard. It is actually very soft. Thatís why SS screws strip so easily. It only gets hard with heat. Keep everything cool and you are ok to use a good hole saw. If you want it perfect you must undersize it then rotary file it. Most hole saws wobble a bit
Having been a machinest/tool maker in a past life, I found the above advice to be right on.

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Old 03-08-2020, 04:24 PM   #24
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Most have hit the problem on the head.
And I reiterate the rules.
Only use sharp cobalt bits. Other bits dull quickly, you apply more pressure , heats the part, case hardens. your dead.
Lots / constant lubricant/ coolant
Steady / constant pressure/ constant cut.

Go to fast and heat the tip the stainless case hardens,,, your dead.
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Old 03-13-2020, 12:45 PM   #25
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If I remember correctly, you should be able to use a Lennox Hole saw if you cut a core out of a sponge that fills the inside of the hole saw. soak it with Stainless Steel cutting fluid.
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Old 03-13-2020, 01:00 PM   #26
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Drilling stainless

Maintain the cut with steady pressure and a sharp bit. Lose the cut and spin without cutting a chip and you will burn the metal blue and harden it rapidly. Of course coolant is a must.
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Old 03-13-2020, 01:26 PM   #27
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Cobalt bit, slow, plenty of lube. Just like docking.....slow is pro!
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Old 03-13-2020, 02:10 PM   #28
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I need to drill a 30mm hole through a 4mm plate without the result looking like a beaver had a go at it. Tungsten Carbide or Titanium tipped/coated saws, wil either do it or is one better than the other. Cheers
Cobalt tipped drill bits are what's traditionally used for drilling stainless in the marine industry.
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Old 03-13-2020, 03:51 PM   #29
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For a 30 mm hole in 4 mm stainless plate, I would find a shop that does plasma cutting. Shouldn't take them more than a few minutes once it is set up. Plasma makes a pretty clean cut in any conductive metal including SS.

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Old 03-13-2020, 09:16 PM   #30
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same advice as prior posters use cobalt bits with lube pressure low rpm slowly. Don't overheat. Harbour freight sells a nice cobalt set relatively cheap if using a coupon etc.http://https://www.harborfreight.com...g_q=drill+bits
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Old 03-14-2020, 12:24 AM   #31
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Low pressure is not the key to drilling in stainless steel. 304 or 316 are both soft materials in an annealed state, as soft at mild steel or aluminum. Both materials work harden badly if rubbed but not cut. You start with a 35ksi material and work harden it to 80ksi, about the same as hard alloy steel. You must cut at least 0.001 per cutting edge, and preferable 0.002 to prevent this from happening. That is why steady feed (preferably power feed) from a drill press is highly desirable. In a CNC machine with very reliable feed rate I can drill hundreds of holes through stainless with an ordinary HSS or cheap cobalt bit without sharpening. SS does generate a lot of heat and you want to keep the tool cool, however most of the problems people have are in not cutting the material, but rubbing it and work hardening it. The only way to get sufficient pressure with a bit over about 1/4 is to step up the size incrementally so all the pressure is concentrated on a small cutting edge. If you use light pressure you may eventually wear through the material, but it is a lot of extra effort and will ruin the bit.
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Old 03-14-2020, 06:23 AM   #32
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Nobody has mentioned water jet cutting. Would that be an option? I know nothing about it other than it's existence.
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Old 03-14-2020, 07:20 AM   #33
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Nobody has mentioned water jet cutting. Would that be an option? I know nothing about it other than it's existence.
I have had lots of metal cut on a waterjet. Piece of cake, but not that many of them around compared to plasma cutters.
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Old 03-14-2020, 08:46 AM   #34
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I never tried to drill a hole that big in stainless. When I need something like that, I drill multiple small holes and finish with files or my Dremel chucked with the solid carbide bits.

Sounds awful, I know. I twice cut 3/8” x 5” long curved slots in 1/4” 316 stainless with this method. Looks fine, works as intended.
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Old 03-14-2020, 08:50 AM   #35
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I have had lots of metal cut on a waterjet. Piece of cake, but not that many of them around compared to plasma cutters.

But a much cleaner cut with a water jet, right?
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Old 03-14-2020, 11:24 AM   #36
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Having been a machinest/tool maker in a past life, I found the above advice to be right on.

Personally, I would have used more cutting oil, cheaper than dulling the drill bit.
Also, start with a center punch. Watch the color of the chips. Dark blue, slow the drill down.... Just MY opinion.
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Old 03-14-2020, 11:31 AM   #37
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But a much cleaner cut with a water jet, right?
Waterjet does make a clean hole, HOWEVER the cut is not straight. The upper surface will be a slightly smaller diameter than the lower surface.
Similar to "die break" on a pierced hole.
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Old 03-14-2020, 12:12 PM   #38
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A waterjet will make a clean cut. Except for the most sophisticated ones, you will get a slightly beveled edge (but you will with plasma too). The hole will be fairly accurate, as good as a hand held hole saw, but not as good as an annular cutter or milled hole. If you waterjet polished stainless, it will dust the area next to the kerf.
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Old 03-14-2020, 08:44 PM   #39
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I need to drill a 30mm hole through a 4mm plate without the result looking like a beaver had a go at it. Tungsten Carbide or Titanium tipped/coated saws, wil either do it or is one better than the other. Cheers
That’s a job for a ‘Peck Drill’. It’s basically a drill press, slow turning, and reciprocates into/out of contact. Oil is important. The main thing is keeping the stainless from getting hot at the drill site. Cobalt bit is also critical. Manually, with a drill press, go hard but for short bursts.
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Old 03-15-2020, 12:04 AM   #40
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The critical thing is to drill slow, slow and keep the SS cool. Stainless steel work hardens with heat and increases resistance as a dull bit stops cutting. Slowest possible speeds on a drill press with tungsten carbide bits.
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