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View Full Version : General Metalworking Good Drill Bits for Stainless Steel



Carroll Courtney
09-30-2013, 7:07 PM
Guys I am looking for a decent set of drill bits that will easily drill throught stainless steel.Guys I don't have deep pockets so I can't afford a set that Nasa uses but I am looking for a 29pc in those nice metal cases.This will be strickly for metal working,no woodworking,any suggestions,what to look for, and links???Thanks---Carroll

Dennis Ford
09-30-2013, 8:06 PM
I used to drill quite a bit of stainless while working offshore (mostly 10 ga or less). I did not find any bits that would do it "easily", Cobalt bits tend to be better. Slow speed and heavy feed pressure with ample coolant will do the job, which means that you need a drill press with appropriate speeds. If you have to drill with a portable drill, keep the speed VERY slow and press HARD.
Stainless tends to work harden so you must keep cutting through the hardened layer every revolution, if you let up on the feed for an instant, the hardened layer will be too thick and will ruin your bit.

Carroll Courtney
09-30-2013, 8:45 PM
Thanks for the reply Dennis,I need a good set of drill bits so I thought I would get the 135*tip made out of cobalt.I just look over at Grainger and the price is way out of my league.I do use cutting oil,and a steady pressure while drilling to help prevent case harden layer.This past weekend I was drilling 3/4dia bar 303 SS for setscrews,while drilling for a pilot hole the bit would slide off center.Then I tried alittle bigger bit for a pilot hole and it did do better using my DP.I think that my tips are 118*,was told that the 135* would work better.Just been price shopping and comparing so far----Carroll

Bruce Page
09-30-2013, 9:04 PM
While not cheap, M42 cobalt works well.
use a center drill to center the drill bit.

Bruce Boone
09-30-2013, 11:22 PM
For better pricing, try use-enco.com

Scott T Smith
10-01-2013, 11:31 AM
Very good advice from Dennis above. I've actually been drilling stainless this morning...

My favorite all-around drills that work well with Stainless are the Magnum buts manufactured by Norseman Tool. http://www.fairburyfastener.com/norseman.htm

Use a good lube and drill slow so as to minimize work hardening of the stainless.

Scott

Scott Shepherd
10-01-2013, 7:09 PM
Like mentioned above, speeds and feeds are more critical and anything with stainless. You also need to fully understand figuring speeds out. A rough ballpark (forgive for doing this from many years ago off the top of my head), is about 50 surface feet per minute. You calculate the RPM by using the following formula :

3.82 x SFM(in this case 50)
_______________________
Drill Diameter

So for a 1/4" drill, you'd have :

3.82 x 50
________
.25

That would equate to 764 RPM.

I always described Surface Feet Per Minute like a speed limit. Each material has it's own "speed limit" for being cut with various other cutting tools. Running way over the speed limit for what the material and cutting tools were made to do and you'll burn up the drill and work harden the stainless. Then you have a much bigger problem.

Calculate the right RPM, get as close as you can to it and use that cutting oil and you'll be just fine. Stainless likes steady pressure. If you dwell and baby it, it'll work harden as well because it's doing more rubbing that cutting.

Just my opinion.

John Coloccia
10-01-2013, 7:20 PM
There aren't any good bits for stainless. Follow Dennis's advice. Stainless...most grades...are just miserable to machine by hand.

Carroll Courtney
10-01-2013, 9:10 PM
Thanks for all the advice,Scott thanks for the formula.I will keep that out in the shop to at lease come close to a working rpm----Carroll

Richard Casey
10-04-2013, 12:03 AM
Carroll, downunder we can buy drills called Artu, and they are all I use for stainless, they are TC tipped, come in sets or individually, so I just buy the Imperial or Metric ones I need, mainly for pop rivets,
rgds,
Richard.

Scott Verson
07-19-2018, 7:24 AM
Depending on the material that you are drilling, HSS https://mechanicguides.com/best-cobalt-drill-bit-sets/ is probably your best all-around choice.For plastic, aluminum and light gauge steel, the price/longevity ratio is tough to beat.
Between fabbing stuff 5-10 times a day for the trucks at work, and general use (drilling through firewalls, extracting stuck bolts, etc), I use my bits pretty much everyday. From my experience:1. Cobalt is best but a good HSS bit is fine if it's from a quality source. I bought a set of bits (1/16 -> 1/2 by 64ths) off one of the tool trucks at work. Ran ~$180 for the set, but the bits are warrantied for breakage, so as long as you keep them sharp it's a reasonable investment.2. Keep them sharp. Most drill bits aren't as sharp as they could be, even out of the packaging. Learn how to use a bench grinder, or even better, a drill doctor (but get one of the higher end ones that will do split points).3. Split points for metal is the way to go. Keeps the bit from wandering.4. Use cutting fluid. It keeps the bit cool and prolongs the life of the bit. Heat kills bits.5. Let the bit do the cutting, not pressure. Apply just enough presure for the bit to work, any more than that and you are dulling the cutting edge of the bit. It sounds simple, but most people don't do it.

Larry Edgerton
07-30-2018, 9:34 PM
Those cobalt bits that Grainger sell are very good, and as you say expensive. I only buy the size I need for the job I am doing when in stainless

andy bessette
07-30-2018, 9:56 PM
Grainger is arguably the most expensive place to shop.

+1 on cobalt drill bits. Mine are Milwaukee.

Bill George
07-31-2018, 7:18 PM
Since ENCO closed down I have been buying a lot of stuff machine shop related from Amazon. Those cobalt drill sets look pretty good.