drilling stainless

[matt k]

Hi, I'm new at working with metal...and am desperate for some help with this situation.

I have a welded assembly (one that's too large to fit under drill press) that I am trying to drill several 3/16 holes in. The material is around 1/16" 304 stainless steel. I bought cobalt drill bits and even tried with a smaller bit first to step up...nothing seems to work. I am going very slow with the hand drill and applying a fair amount of pressure and am about half done my first hole ( after about 15 minutes of trying)...is it supposed to be this difficult drilling stainless material?

thanks for your help

[Blackadder]

my guess is that you have work hardened it bet you put some oil on the drill bit


stainless needs to be cut not rubbed

[gmacoffline]

sharpen your cobalt bit properly and go again. as soon as it stops cutting or even looks like it is failing to cut - stop and resharpen it again. do not run the dull bit under high pressure as it will wallow a big hole or track off into neverland, or just plain break off. this material needs a hard and sharp edge to cut it and if the material work hardens ( as it does so easily) then it will kill the edge quickly. sharpen the drill to the correct angle and profile and it will cut but it wont stop the material from hardening. use proper cutting lubricant for stainless, if any at all. on this size of material I have used dark cutting oil in a pinch and have seen neverseez or petroleum jelly used also.

[gmacoffline]

sharpen your cobalt bit properly and go again. as soon as it stops cutting or even looks like it is failing to cut - stop and resharpen it again. do not run the dull bit under high pressure as it will wallow a big hole or track off into neverland, or just plain break off. this material needs a hard and sharp edge to cut it and if the material work hardens ( as it does so easily) then it will kill the edge quickly. sharpen the drill to the correct angle and profile and it will cut but it wont stop the material from hardening. use proper cutting lubricant for stainless, if any at all. on this size of material I have used dark cutting oil in a pinch and have seen neverseez or petroleum jelly used also.

[Doug_C]

I'd have to echo the sentiments of the rest of the responses on the work hardening of the material. There is a limit of 3 to 5 revolutions of the bit if not pulling a chip when hardening will occur.

With a fresh sharpened drill. Pay attention to the color of the chip based on the RPM of the cut. If they turn blue, the RPM is too fast or the bit has become dull again. Once the cutting edge is compromised, the work hardening takes over. In many cases effecting the surrounding material. Any dwell while it is not cutting has an immediate impact on the material below the bit. It may take a new edge just to get passed it. It may very well show up again when attempting to step out the hole with another cutting tool.

I would not expect the SS to harden from the welding, but that could be a factor too if you are drilling in close proximity to the welds.

DC

[Jacin]

Stainless can be a bear!!!! As already suggested - work hardening it can your biggest problem - ya gotta add some oomph sometimes. Problem is that using a small bit free hand can pose it's own challenges - and using the full size makes the force required even higher!!! So IF it were ME I would try a couple things - first off I would put in a starter hole - probably an 1/8" dia or so - I would use a VERY short bit or one with very little flute length - either of these will allow you to bear down on it more than a "standard" bit. And if that still didn't work I would go get a small center dril - something I use a LOT for spotting hand held drilled holes - they are VERY controlable (won't walk - especially if you center punch the spot) AND you can really bear down on them if necessary.

Works for me!!!!!!

Good Luck!!!

[matt k]

Thanks all for your advice. I'll try some of the tips mentioned. much appreciated

[ED from CA]

Matt
I have drilled about a mile of stainless 303,304 316, while working on aircraft in the early 60's.The way we did it was to use what is known as a brad point drill. The same type point that is used on wood plug dowell holes. We use to grind them ourselves, with a point in the center , which will follow a center punch mark, and drill a nice round hole. I have seen them now for sale at Harbor Frieght about $8.00 - $10.00 for a set of about 6 or so of the standard fraction sizes.Once you have used these type of drills, you will love them. Don't forget to use some lube on the drill, I used Molly-Dee lube , but don't let it stand around any metal that is not stainless, as it will RUST it! So wipe it off when you are finished drilling, even overnight. Well Matt, I hope I was some help, on this. I always said if I cought the guy that invented STAINLISS STEEL !!!!!!! We used high speed steel drills and didn't have a problem, now you have Cobalt,and other hard coated drills to choose from, which should be a snap.


Hope it helps See Yaaaaaaaa ED

[D_R]

Besides the cautions that have been mentioned, be sure to support the workpiece from the back so it isn't allowed to deflect away from your drill bit. That deflection with the bit rubbing, rather than penetration, will cause workhardening.

[bulldog]

get some condensed milk. it works wonders on drilling stainless. trust me you will be amazed.

[Steven Dzupin]

Try a blop of Permatex Soft Set Gasket Compound.

Just dip the tip of the drill into it before you start the hole.

Works but I don't know why.

Try it ,you might like it.

Regards,

Steve