Posted: 5/19/2016 10:55:28 PM EDT
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Well, yesterday I drilled 366 7/64" holes in thin stainless. Used one HSS (purchased for this project) bit and oil, no problems. I had 4 larger holes to punch (through 1mm stainless), so needed to drill the arbor (?) holes for the 13/16" greenlee punch. I killed a few harbor freight bits in the process of drilling the first one. Before I head over to the hardware store, need to figure out what I should get. Other than a pilot hole, how many step bits should I get to go from 7/64" to 1/2"? Should I even be using multiple bits to drill the hole? |
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I buy about $5000 a year in drill bits for a production machine shop.
What I've Learned about Chinese HSS is it doesn't matter which end you put in the chuck - the end result is the same. Buy a good quality Cobalt steel drill bit from a reputable firm. Stainless is a very poor conductor of heat so it builds up fast in drilling a hole. HSS high in cobalt resists this heat. ETA: A lower speed and a squint bottle of coolant will help |
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Quoted:
a hole saw? maybe if your stainless was made of wood. We use carbide and regular hole saws on stainless every day. Its fairly common. Op, in my experience i had trouble tearing the shoulders off of bits by stepping in ss. I always used one bit. That was in the field though. If you are on a mill try an annular cutter if you have one or step it 2 or 3 times with drills. A good bit will chew right through it. I was a welder at the time. Didnt know shit about drills. I just bought the nice indexes that mentioned ss and cost a lot. It was cheaper in the long run. |
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13/16 shaft on the KO? I'd run with a 7/8 hole cutter. By this I mean a 7/8 hole saw with carbide teeth that is made for drilling harder metals. A standard hole saw isn't going to last for shit. Go 1-1/8 if you want some play for your KO. Step bits (I call the mini-bits) are expensive. I wouldn't use them on stainless.
Here is an example of what I am talking about. Remember, for stainless you push hard, go slower RPM & lube it... |
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Quoted:
13/16 shaft on the KO? I'd run with a 7/8 hole cutter. By this I mean a 7/8 hole saw with carbide teeth that is made for drilling harder metals. A standard hole saw isn't going to last for shit. Go 1-1/8 if you want some play for your KO. Step bits (I call the mini-bits) are expensive. I wouldn't use them on stainless. Here is an example of what I am talking about. Remember, for stainless you push hard, go slower RPM & lube it... Good point on pushing hard. I did nothing but stainless fab and welding. Some of the wall plates i made had 40 or 50 holes in them. Id put all my body weight on it and just enough speed that it turned and didnt burn up. I always got a lot of life out of my hole saws and bits. |
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Good hole saws for stainless sheet metal large diameter hole making are the way to go. When using a twist drill bit and stepping up go up by a half, IMO. 1/2" hole = 1/8th to 1/4 to 1/2. This will usually not chip the edges off the bit to badly. Sheet metal with twist drills... YMMV. Create a test drill sequence to validate your process.
As others have mentioned use plenty of lube, heavy lube and slow speed. Have plenty of extra bits too since SS is the devil metal and will school you in every way 
Cheers ILB |
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Need to get up to about 1/2" to use the 13/16" knockout punch. I think the punch uses a 3/8" arbor, but the knock out bends and will get stuck if the arbor hole is too small. FWIW drilling pots for homebrew bulkheads. Brew Kettle, Mash Tun, and Hot Liqueur Tank. 13/16 is the size needed for 1/2" fittings. Drilled the false bottom (essentially a colander) for the bottom of the Mash Tun yesterday, punched a hole through it for the pickup tube and the hole in the Mash Tun. It hardened and was a beast. |
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I have never used a quality step bit, I have used a cheap one on mild steel with some success. The company that sold the pot sells a hole saw to cut the 13/16" holes. I have always had hole saws want to drift on me. I went with the greenly punch as it cuts a smooth final hole. A rough hole will result in a leaky bulkhead fitting. |
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1mm sheet stainless, 1/2" hole?
BE SURE TO CLAMP THE WORK PIECE DOWN, WELL.
But, seriously, do it. Lock your quill some, too. Helps keep the drill from sucking through. If you buy a 1/32 under which is 15/32 and then the 1/2 you'll get a nicer hole with smaller burr on the back side. If you radius the corners on the finish size drill, it'll leave a nicer finish. Just follow the relief angle on the flute corner and knock about a 1/64 radius on it with a stone or diamond file. |
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Quoted:
I buy about $5000 a year in drill bits for a production machine shop. What I've Learned about Chinese HSS is it doesn't matter which end you put in the chuck - the end result is the same. Buy a good quality Cobalt steel drill bit from a reputable firm. Stainless is a very poor conductor of heat so it builds up fast in drilling a hole. HSS high in cobalt resists this heat. ETA: A lower speed and a squint bottle of coolant will help |
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Quoted:
Here is a picture of the mash tun. Still need to drill out the 2 other pots.http://i1306.photobucket.com/albums/s571/Mousehunter1/IMG_1387a_zpsckw7nolc.jpg |
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you need a sheetmetal drill
http://speedex.com.au/index.php?route=product/category&path=111 |