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Drilling Stainless steel

coman61

coman61

Well-Known Member
Anyone know of a good way to drill stainless steel. It would not be bad if it were only 1 or 2 holes but in this case it's more like 10. I bought a kit amp from that auction site that came from China. Well it looks like somewhere along the line they changed the transformers and keep the chassis the same.:mad: So far I have made 4 bits so dull they don't cut anymore:thumbsdn: and broke one while haveing a hissie fit.:nono: I know they say speed and pressure matters the most but at this pace it will be a week before I get my holes cut. I was thinking about going to a buddys house who has a plasma cutter but I don't know if that will make the holes too large. Looking for about 1/4" holes.
 
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Low speed and high pressure with some lubricating oil will work. You can also start with a smaller pilot hole and move up in size to your 1/4"
 
Yeah, I tried that once. Burned out a few bits until I learned you need Cobalt drill bits. And I don't mean the brand from Lowes Home Center. And they are pricey too. Good luck.
 
Yup carbide. You will need those. Maybe Chinese carbide drills will cut thru Chinese stainless. Do their drills cut to the right or the left? :D
 
To reiterate--low speed!Sharp bit! Coolent! I drill and cut stainless everyday.A variable speed drillpress would be handy.
 
I've done it on a drill press with carbide bits, slow speed and lots of oil. Several hundred holes, three or four bits were trashed in the process. I don't think I've ever forgiven my dad for giving me that job. :D
 
Most likely the tool you were using had a up-sharp cutting edge, once it breaks down the tool just keeps going until catastropic failure. Actually a good HSS drill with proper geometry and no coolant would work as well, if your using a milling machine or decent drill press pilot hole should not be necessary.

Basically your trying to use a tool meant for plastics, wood, soft metals, you need one suited for hard to machine metals. A lot of stainless steels have a tendency to work harden due to composition, if this is the case slowing the feed down only worsens this condition snd also causes tool to fail. The difference is that the tool you want would have a hone or edge prep along cutting face to toughen it up, that stainless can get pretty rough. I also garee that home depot or lowes will not have what you need, try production tool or msc industrail supply.
 
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Stainless is very malleable. VERY tough but also VERY gummy. I work with stainless every day. All our injection plants are stainless plumbed, with stainless pump mounts etc.
Supertanium brand bits work best, Those who have spoken before me are correct. SLOW rpm, LOTS of coolant , MEDIUM to HEAVY feed rate.
Tungsten carbide bits are good if you can clamp in a mill vise or clamp on a drill press table. If theres ANY movement of the stock the bit whistles accross the shop.
All our stainless pipe is threaded in a small Monarch manual lathe or a hollow bore.
Next time you buy stock stay away from any 400 alloy, 316, 309 317, alloys also machine tough. 304 is the most machine friendly, try some next time.
 
similost said:
CNC with carbide :thmbsp:
Click to expand...

I've been working with stainless for 15 years or so. Carbide is overkill and brittle.

High speed steel is fine. I drill / and tap SS with a hand drill all the time.

As said by a couple others before me, slow the drill down a bit, keep pressure on the bit, lubricate to keep cool. You can't push too hard. When teaching new hires to drill SS (Typically with a hand drill, into 1/4" walled tubing) the phrase "You got to get all your s#@t behind it." comes up a lot. Drilling a pilot hole helps a tone but a 1/16 drill bends under the pressure. Instead, use a center drill if you have one. It has a short small bit that ramps up quickly to a heavy shoulder. It is also @ 1 1/2" long, make it a bit more stable.

The problem with stainless is that it work hardens easily. You have to stay ahead of it. slack off enough to stop cutting and the spinning drill will harden the top of the cut and then burn up the drill.
 
Try punches(Greenlee etc...).
I did a bunch in SS sinks, for soap holes. My punch set was hydraulic instead of wrenching, but that shouldn't make a difference.
 
I have a drill press but I'm going to need better bits. The artic air is sopposed to come in tomorrow afternoon. Maybe that will keep it cool.:smoke::scratch2:
 
JustA thought... If you want to try something with your existing bits, take a stone to the cutting lips. What your looking to dop is just knock the sharp edge off, maybe about .003-.005 rad honed edge. This will build the cutting edge strength up and make the tool less grabby. It will allow you to push the drill like you need to in ss.

This will not help with the problem of drill grabbing and breaking once it breaks through the sheet metal. If this problem is causing tool breakage this is where you would want to use a pilot drill.
 
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You don't need a pilot hole to drill a 1/4" hole. Buy good quality bits and you will be fine. You are probably looking at at least $20 for a small set. Good bits aren't cheap but are worth the extra money. Like others have mentioned slow speed is key with stainless.

Don't get wimpy on the pressure but don't hang on the drill press either if you know what I mean. Water works just as good as anything for drilling. Everyone thinks that you need to lubricate a bit with oil where in reallity all you need is to keep the bit cool. It's much easier to clean up too.
 
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