Problem drilling CPM S30V

flatgrinder

flatgrinder

Joined
Dec 20, 2005
Messages
2,045
I bought some 1/8" thick CPM S30V from Jantz Supply recently and it seems like it left the mill hardened in certain areas. Anyone else experienced this?

I drilled a 3/16" and a 1/4" hole, then tried a 5/16", the drill bit squeeled half way through the steel and ended up rounded off. I tried this using 3 (2 HSS and 1 cobalt) drill bits before eventually getting through -but killed all the bits.

I've worked with CPM S30V, D2, ATS-34 and never had a problem before. The speed on the drill press is set at the slowest and I haven't had to replace a single drill bit before.

Anyone have any batches of CPM S30V that had certain spots that they just couldn't drill? Or is it just me? I used a lot of precision ground D2 last year and never had a problem.
 
I have drilled and tapped ATS34, 440C, and S30V to put 1911 bushings in the handles for 1911 slab sided knives. I had more success with S30V than everything else. Of course I was dealing with 5/32, 3/16, and 1/4 inch stuff.

I am thinking that this is more of a issue with thinner stuff. As I don't have any experience with the thin stuff I would look up crucible's number online and give them a call. I have had OUTSTANDING service from them and drive over to their supply depot when I need more.

Other than being sure to center punch and use drill pilot holes I got nothing.
 
Although not my favorite to drill or machine CPM S30V has posed no outstanding difficulties as yet for me. I have worked it up to 1/4 inch in thickness. A bit off subject; I just hate having to clean the surface bark off that stuff before starting work on it. That's part of knife making though. I know you are too experienced not to know to use cutting oil so I will not even mention that except for already mentioning that. I think this one is for Mete to chime in on. I wish you luck. I know how very expensive S30V is and to run into this problem hurts. Maybe if no other resolution is economical enough a carbide bit or two could pull this batch out(?).

rlinger
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Flatgrinder: S30V is no problem to drill. You need cobalt drills, and you need good quality drills, or at least sharp ones. Don't let the drill spin in the hole once you atart, either.

A 5/16 Diameter hole is good sized. I don't know how slow your machine goes, but, it may well be on the "fast" side of slow. So, lubricate that drill, or at least cool it with H20. Cobalt drills will work.
 
I agree; I too use cobalt bits and not at high speed. EDIT: Oh my, I just went back and read your post again. I see now you used HSS bits to begin with. That in itself does not really explain a lot unless the hole got work hardened from the HSS bits dulling and continuing. That could help explain, possibly, the ruination of the cobalt bit. You may have work hardened the hole(s). Try a sharp cobalt bit in a non-essential area of tang as a test. If it drills well you know the answer.

rlinger
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The first lesson in Machine Shop class is how to sharpen drill bits to avoid this same problem. Be sure to use the slowest speed possible and flood it with coolant. Go slow and clean the chips often.
 
Sorry, I should have mentioned them in order. I used the cobalt bit first and then the 2 HSS bits to finally get through the material.

I don't know why, but this piece has been giving me some grief. I've never had this problem before, but when I received it, the piece wasn't truly flat so I stuck it in a vice and straightened it using my blade straightening jig, barely put any pressure on it (couldn't even see any flex) and it shattered like glass. I thought this was annealed! The grain looked fine through the first 3/4 of the width, but the last 1/4 it looked like it could have inclusions or something (basically, it wasn't a clean break through the other side). If it is annealed, it should not have cracked right?

Here's a photo:

The difference in grain structure at the top of the steel in the photo is a lot darker, while the rest is a lighter gray. By the way, I deliberately flexed other parts of the same steel and other parts did not crack. Kinda leads me to believe that certain "hot spots" were hardened.

Any ideas?
 
I have had some weird stuff happen with CPMS30V. I had a piece of 3/16" show up with what looked like a scratch across it, a couple of inches from the end. I flexed it, barehanded, to see if it was a crack and the whole piece broke off! Now I am NOT a big guy and in any case I wouldn't expect that from any steel.

I am reluctant to make anything out of the rest of that bar. . .

Dave
 
I am a Tool and Die maker so I have had a lot of experience with drilling and minning all kinds of CPM up to 6" thick. Not to beat a dead horse, but make sure you run your drill slow, sencond we often use tapping fluid instead of coolant on steals like that (a light oil will work or even motor oil) but use pleanty of it and dont use alumkinum tapping fluid (its to thin). Make sure if you sharpen your own drills you have enough relief on it. Sometimes it is also really helpful to take a carbide burr in a die grinder and remove the top .075 off around your center punch where you will be drilling, this removes the hardened outside(there shouldnt be scale). when you first get your steel run a file across it if your file wont scratch it the supplier screwed up and work hardened it in the mill (good files are rockwell 65c as a rule of thumb) return it. If you file scratches it you will be able to drill it. A masonary drill is also used sometimes to get another drill started, if you do this run it FAST run coolant like mad, but first sharpen the bit, they come out of the package ready to drill concrete not metal, they should have flats that come to a sharp point. They do also sell carbide drills that will cut through it like its butter but this shouldt be necessary.
 
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