Best Drill Bit for 316L Stainless?

Help!
I'm so f*cking tired of destroying drillbits going through 316L Stainless Steel.
I've got my drill press at 250 rpm, and I push as hard as I dare to stay ahead of the hardening of the stainless as I bore through, but I
still find I'm throwing a lot of bits away.
I've tried $1 bits to $6 bits (1/2") and they just dont cut it, so-to-speak.
Suggestions?
Anyone in the Port Orchard, Washington area have a metalworker that'll punch 1/2" holes into Stainless?
Thanks, James, Seattle
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RainLover wrote:

You might consider acquiring the capability to sharpen drill bits. Also, you might consider going to a different concept than drilling. For example, you could try a rotabroach, which is like a hole saw and also like an end mill. You could also invest in a solid carbide end mill -- well, I don't know how well that would work in a drill press.
AFAIK you're our entire population from Port Orchard, James.
Grant Erwin down in Kirkland
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snip----
You could also invest in a solid carbide end mill -- well, I don't

Bad idea. Not in a drill press. Hell, not even in a mill! Drilling with end mills is never a good idea, not even with center cutting end mills, especially in material that is difficult to machine. Drills have a margin that is not relieved (circular ground instead of backed of with a clearance angle). That helps prevent the drill form wandering and cutting oversized. End mills are intended to cut on their sides, and plunging them gives them every reason to do so. A flimsy drill press (and they all are) allows the end mill to wing, creating severely oversized holes, and can be quite dangerous in the process. Further, the typical drill press chuck is *not* intended to grip hardened objects. They rely on their ability to indent soft shanks for gripping and driving power.
This is likely a very good place to try one of the parabolic drills mentioned by Jim on a different thread. I have no personal experience with them, but gather they are a nice solution for difficult drilling projects.
Otherwise, I'd suggest the use of cobalt drills, and step drilling the hole. I'd consider the idea of drilling a pilot hole, something on the order of 3/16", so it will feed easily, then following up with the desired drill size, assuming you don't have to pass an inspection of sorts and a slightly oversized hole won't be a problem. My experience with drilling stainless tells me it's not a good idea to double drill holes by leaving only a small amount to remove when opening up the hole.. I've cleaned off the margins of more than my share of drills in that fashion.
Be very mindful of how the drill is cutting, and get out of the hole instantly when you hear it start complaining. At that point, you're already experiencing edge failure and that leads to serious work hardening, followed by margin destruction and broken drills. The resulting hole will be so hard that a new drill that is introduced is destroyed instantly, too. Avoid, like the plague, a drill that cuts but squeals and chatters as it does. That is usually a perfect indication that the hole is work hardening on you.
Are you lubricating the cut with sulfur based oil? How deep are you drilling? Thin material tends to be more difficult that thick, and might be your problem.
Good luck!
Harold
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If you don't mind driving to Bremerton, a company called JPL Habitability can punch the ss for you. Ed Angell Poulsbo, WA

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Cobalt bits work best. Lots of pressure, and lots of cutting fluid. Water/oil emulsions work best.
I have never had that much trouble.
If you visit me in Renton I can teach you how to sharpen bits by hand.
A rotabroach would be a better solution, but the bits are about $15 each.
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My son discovered a better way to sharpen drills for 316SS. I reported on it in this NG and it was pointed out that he had re-invented a known concept - the Raycon drill point. It really helps, here's a link showing pics http://www.winsloweng.com/articles/grindPerform_content.htm This solves the problem of the edge of the flute dulling right away.
Karl
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Try a .50 BMG, faster too.

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On Fri, 29 Oct 2004 18:47:33 GMT, "Tom Gardner"

and marvelous fun.
Gunner

"By calling attention to 'a well regulated militia', the 'security' of the nation, and the right of each citizen 'to keep and bear arms', our founding fathers recognized the essentially civilian nature of our economy. Although it is extremely unlikely that the fears of governmental tyranny which gave rise to the Second Amendment will ever be a major danger to our nation, the Amendment still remains an important declaration of our basic civilian-military relationships, in which every citizen must be ready to participate in the defense of his country. For that reason, I believe the Second Amendment will always be important." -- Senator John F. Kennedy, (D) 1960
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wrote:

Is BMG a Brand?
I appreciate all the advice on this issue. I'm currently using just a off the (homedepot) shelf cutting oil as lubrication and I'm going to be drilling my 1/2" holes into 1/2" thick 316L Stainless.
James, Seattle

nation, and the right of each citizen 'to keep and bear arms', our founding fathers recognized the essentially civilian nature of our economy. Although it is extremely unlikely that the fears of governmental tyranny which gave rise to the Second Amendment will ever be a major danger to our nation, the Amendment still remains an important declaration of our basic civilian-military relationships, in which every citizen must be ready to participate in the defense of his country. For that reason, I believe the Second Amendment will always be important."

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I'm so sorry, I was having fun by thinking of putting holes in your SS with a "Browning Machine Gun" (BMG) The .50 size would be right and like Gunner said it would be more fun than drilling.
This would be a job for cobalt bits and coolant. Use slow speed qnd high pressure.

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On Mon, 01 Nov 2004 19:30:45 GMT, "Tom Gardner"

Hey, as long as the holes are consistantly around the edge (retangler shape), bring your Browning over and do some Machining on my 316L Plate... bring it on!

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On Fri, 29 Oct 2004 07:42:34 -0700, RainLover

Greetings James, I feel your pain. I hate 316 SS. If you drill a pilot hole about 5/32" and then go through with the 1/2 drill life will be easier. Use cobalt split point drills. You could speed up the drill to 350 rpm but You'll be better off at the lower rpm. Water based coolants work better than the sulfur based cutting fluids. I proved this just recently on a 304 SS job. It was amazing how much better the finish was and how much better the tool life was. I think it's because the water keeps things so cool. BTW, I use a coolant that Cutting Tool Control in Ballard sells. Made by Swisslube, it's called Blasocut 2000 CF. The CF means it's chlorine free. Chlorine does have advantages but I try real hard to have a shop as environmentally benign as possible. Island County sent over a rep to look at things and she said it was one of the best shops she had seen as far as environmentally polluting things go. Anyway, the Blasocut stuff is good and it smells like play-dough. And doesn't taste as near as bad as Trim-Sol. Also, if you need to get rid of it separation occurs if salt is mixed in. So the stuff will rise to the top and you can dispose of it on you neighbor's driveway or the local recycling station. The salt water can be dumped on your neighbor's blackberries. Or not. Depends how well you get along with your neighbors. ERS
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RainLover wrote:

Look at the end view of the drill bit. That web in the center has to be pushed through the material you are cutting. Stop killing yourself, screw the fancy split points, just drill a 1/8 hole first, then the 1/2 drill will cut through a hell of lot easier. How thick is the part you are drilling through? Remember, if chips are not rolling out then you are either dulling the drill bit or work hardening the stainless. The objective is to always keep the chips coming.
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Hi James, Some great advice already, just my two cents worth.
If you drill a pilot hole, make it just a tad under the width of the chisel edge of the next drill. That way most of the resistance caused by having to push the chisel edge through the stainless is gone, but the ends of the chisel edge can still hold the drill on centre. I've found that drilling a pilot hole larger than the width of the chisel edge can cause the drill to wander and wobble, as the drill doesn't have anything left to anchor it on centre.
Another tip, the old fashioned high carbon steel drills can be harder than high speed steel drills. The benefit of high speed steel is that it's hot hardness is much higher. If you can keep a high carbon drill bit cold, read slower speed with flood coolant, it will drill almost anything. The main benefit of all the newer technology is production speed, sometimes it's OK to just be able to get the job done at any speed!
regards,
John

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A quick look into Machinery's Handbook 25th edition, page 1030, Table 19 shows a recommended drilling speed for 316 stainless steel at 50 fpm. (316L is leaded, right? Should be somewaht faster?)
So why so slow? .....30*4 / .5 = 240 RPM ..... vs 50*4 /.5 = 400 RPM
If you don't own a copy of machinery's handbook, it would be a very good investment. A lot of valuable information in it besides recommended drilling speeds, feeds, coolants, etc.
Coolants? Are you using any? How about the rigidity of your setup?
Have you tried reducing the relief angle on the twist drill? ie sharpen normally, then touch briefly on wheel to produce a "land" approx. 1/32 inch wide on each flute. End result, if done correctly is to provide a bit more resistance to edge breakdown.
Another possible solution is to hone/grind a very slight radius onto the corners of the margins, to emiminate the sharp corner...
As for punching holes, the thickness of your material has "loads" of bearing upon the feasibility of doing same, in addition to the final cross section of the hole itself.
Good luck!

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wrote:

<snip>
No, low carbon. It's less prone to chloride stress cracking than regular 316.
Pete Keillor
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RainLover wrote:

It sounds like you are not drilling a series of expanding hole sizes. A large drill like a 1/2 does not cut the center part of the hole very well. The tip thens to waddle in the puddle.
If you drill a small drill first then step up, the slow speed center part will be drilling air while the edges can dig in and cut the proper hole.
Martin
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Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer snipped-for-privacy@pacbell.net
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James,
1/2" holes in 316L. On a drill press. Not exactly the best choice of machinery, but OK. It won't exactly be easy, but it will work. What are you using for coolant? Are you flooding the workpiece and drill? How deep is the hole?
See if you can get your hands on some Nachi Cobalt's w/Split Point. I use them with OIL (Cut Max 570) for drilling 1/2" dia. x .625" deep holes in 316L all the time (about 1000 pieces per month). Get somewhere between 300-350 pieces per drill, depending how close I watch it to keep the chips from blocking the oil flow. 1000 rpm, and a .003" ipr feedrate. I'd like push them harder, but my machine won't handle it.
The Nachi's are rather inexpensive (much better than $14 Guhring GT-100's), I think around $6 or $7 each for 1/2". So cheap in fact, I really didn't expect them to last long. Wrong! Every diameter I tried worked so well that I've now filled up my drill cabinets with nothing but Nachi's.
The pilot hole that some have suggested works well if you're only making a few pieces, but if you're running production, you have to go for it with the 1/2" drill. You can't make any money standing there changing drills all day.
With a good split point drill, a rigid set up, and plenty of coolant (you need a flood), and a strong right arm, there's no reason you can't carve that 1/2" hole with a single drill.
Matt
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