Replies

1. 
   Len | May 19, 2003 05:34pm | #1

   Unibit makes a carbide hole cutter. A bit pricey for one hole. About $50.

   Do you have a portable drill press? Or a way to steady your drill? I've cut through stainless at least that thick with a bi-metal hole saw. Drill at a slow speed and use a lot of cutting fluid.

   Otherwise you could drill a smaller hole and use a jig saw to clear most of it. Clean it up with a file.

   Len

1. 
   Forrest | May 19, 2003 05:36pm | #2

   Slow speed, that might do the trick. I was using the hole saw at high speed. Thanks!

   View Image

   Edited 5/19/2003 10:37:25 AM ET by GasCap

1. 
   timkline | May 19, 2003 07:46pm | #4

   You overheated the bit. Take a new holesaw and use it to drill into an old sponge, filling the holesaw completely. Then saturate the sponge with cutting oil preferably or whatever oil you have around. Take it a little more slowly next time. You should be able to get at least 5 holes with this method.

   carpenter in transition

1. 
   clampman2 | May 20, 2003 03:55am | #7

   Tim,

   Great tip with the sponge. Thanks.

   Clampman

2. 
   billyg83440 | May 19, 2003 05:53pm | #3

   It could be your drilling method. Get a good name brand bi-metal hole saw, just one (Lenox, Morse, Greenlee, Klein, Dewalt). Also pick up some tap fluid (TapMagic is what we use at work), or even some 3-in-1 oil. Use a variable speed drill, keep the speed low, and use the oil to lube things.

   If you spin that big a hole saw fast while cutting stainless it'll overheat and ruin it.

   The cheap import sets that say Bi-Metal on them are generally junk. Never seen one that held up to drilling mild steel much less stainless.

   According to the machinists handbook. Stainless should be drilled at 90 fpm (feet/minute). This means the teeth of the saw should only travel 90 linear feet in 60 seconds. So 1.75(Dia.) x pi= 1.75*3.14= 5.5 (5.5" circumference). 12/5.5=2.18 (2.18 rpm = 1 fpm). 2.18*90=196 rpms. On a milling machine I'd set it about 200rpms to drill your hole. With a drill I'd drill as slowly as possible, use lots of lubricant to keep things cool, and take a break during the cut to allow things to cool down. Real easy to overheat things. When cutting big holes in metal, slower is better.

3. 
   IMERC | May 19, 2003 08:25pm | #5

   A chassies (sp?) punch will cut SS holes for years. The same ones used to punch holes in electric cans and boxes.

   Piolet the hole with a metal rated brad point (B&D, DW). Use a lot cutting / cooling fluid / oil. In a pinch ice will work. Start drilling using slow speed and steady uniform pressure. Maintain the same pressure all the way thru the drilling cycle w/o pushing too hard and forcing the bit.

   Greenlee makes a "slug buster" rated for some pretty heavy SS. 12 ga I believe. The punch will give you a clean ready to go hole. They can be had with an array of threaded shaft (1/4 - 1/2") sizes. Load bearings and and a bunch of other options.

   If you use a punch oil it with Tri-Flow or similar. WD-40 can't seem to take the pressures.

4. 
   Bruce | May 20, 2003 12:05am | #6

   Slow is the way to go w/ stainless.  As an ex-machinist, I can tell you that I popped many holes in stainless, or sawed through it, with typical tool steel cutting tools.  And you want to literally flood it with coolant of some kind, because the heat build-up will burn off your cutting edge long before it's shot from wear.

   Formerly BEMW at The High Desert Group LLC

5. 
   4Lorn2 | May 20, 2003 06:25am | #8

   Tap Magic or similar helps.

   Low RPMs

   Drill press. It keeps everything square, stable and allows more pressure and control. Clamp the work. Unclamped sheet metal, especially stainless, can bind and cause nasty cuts.

   Far more pressure than you think. The teeth need to remain engaged. If they skate they heat up and chatter. A drill press helps greatly in this.

   If you have to do it with a hand drill try to find a variable pitch tooth design on the hole saw. They cut smoother, chatter less and allow more control. Even in a drill press it helps a bit.

1. 
   JohnSprung | May 20, 2003 09:47pm | #10

   > Far more pressure than you think. The teeth need to remain engaged.

   Right, stainless work hardens quite severely.  You need to keep the tool advancing fast enough that you're cutting a little beyond the material that has been hardened.  Stop and you're in deep s***.  In this case, since the cut has been stopped and the material is hardened now, going to the chassis punch instead of more hole saws would be the best choice. 

   -- J.S.

6. 
   Scott40 | May 20, 2003 08:55am | #9

   Change the pilot drill to a solid rod or turn the drill around backwards to keep the flutes from enlarging the guide hole.  This keeps the hole saw from wandering with the repeated/extended cutting times.  Go slow and use lots of Tap-Magic cutting fluid.

   s