Mapster
Member
I have some heat treated steel parts from work that I am planning on making a pen out of, but the parts just laughed at a fresh HSS bit. Cobalt? Carbide? Carbide boring bar? All tips and help would be appreciated!
Drilling Heat Treated Steel
- Thread starter Mapster
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wouldentu2?
Member
Heat treated to what?
JF36
Member
Your best bit is carbide. Make sure you use a low speed, use lots of cutting oil, and take your time. Do not use cobalt, as you will destroy your bit. Cobalt should not be able to drill through hardened steel, if it does your steel is not properly hardened. What kind of steel are you using?
Paul in OKC
Member
If it is 'just' heat treated steel, regular bits should drill fine. Use some kind of lubrication. If it is heat treated tool steel of some kind, you will need carbide, and that is not a gaurantee.
I work with heat treated steel (4140) all day, and drill it with HSS.
I work with heat treated steel (4140) all day, and drill it with HSS.
Mapster
Member
Unfortunately I am not familiar with the specifics of the heat treat process. It is 12L14 steel and the heat treat process is a few hours long. Regular bits won't drill through the casing hardly at all. Sounds like carbide is my best option. Is there any difference between buying a carbide bit from Enco or a similar machining supply and using a carbide tipped masonry bit?
Rich L
Member
If it's 12L14 it's likely to be case hardened and there are a few methods to do that. In any case (pun), a "real" carbide bit would be advisable to at least start the hole. You don't say how big a hole you want to make but if you want to do a decent job at it then avoid masonry bits. Again, not knowing the size I can't recommend an RPM but it needs to be slow and make sure you get a good bite and keep it going.
I've never tried this myself with case hardened parts but if possible you might want to try to anneal it. Just stick it in the hottest oven you can find for about an hour. That will temper back that martensitic layer that's giving you the trouble.
Another option is to use a dremel grinder to get through the surface and then you'll have soft steel underneath to drill. You don't have to go deep as the case will be well less than a millimeter thick.
Cheers,
Rich
I've never tried this myself with case hardened parts but if possible you might want to try to anneal it. Just stick it in the hottest oven you can find for about an hour. That will temper back that martensitic layer that's giving you the trouble.
Another option is to use a dremel grinder to get through the surface and then you'll have soft steel underneath to drill. You don't have to go deep as the case will be well less than a millimeter thick.
Cheers,
Rich
Dalecamino
Local Chapter Leader
Marshall, I recall Mike Redburn saying, he had a bunch of bits. Check with him before buying at a store or, elsewhere.
designer
Member
12L14 is just 14% carbon with lead added for machineability. To make it easier to machine that is.
With 12L14 after casing it, start your hole with a carbide center drill. It will go thru the case surface without a problem. Pick a size close to your drill size if possible. Then you can go through it easily with a cobalt or carbide twist drill.
Getting thru the case hardened surface will tear up the edge of the cobalt drill though. Carbide would be the way to go. Do they have one at work you could borrow for a night and take back the next day?
Rich can probably give you rpm's better than I can after he knows the hole size.
With 12L14 after casing it, start your hole with a carbide center drill. It will go thru the case surface without a problem. Pick a size close to your drill size if possible. Then you can go through it easily with a cobalt or carbide twist drill.
Getting thru the case hardened surface will tear up the edge of the cobalt drill though. Carbide would be the way to go. Do they have one at work you could borrow for a night and take back the next day?
Rich can probably give you rpm's better than I can after he knows the hole size.
Mapster
Member
Thanks for the tips everyone. I actually have a sleeve type part and I have to open up the inner diameter about 10 thousandths. I need the ID to be .334 and it is currently about .320. It is case hardened, but I have to drill through the casing the whole way. I am drilling about half an inch deep.
Chuck, I will definitely talk with Mike, though I am not sure he has any larger size carbide bits.
designer, I have asked around here at work, but they are too smart to drill through heat treated parts, so no carbide laying around here.
Sounds like carbide is the way to go from everyone's comments, so back to the masonry vs standard bit. I found a masonry bit that is the right size and solid carbide tip pretty cheap. Would this drill cleanly enough since I am only taking off about 10 thou?
Chuck, I will definitely talk with Mike, though I am not sure he has any larger size carbide bits.
designer, I have asked around here at work, but they are too smart to drill through heat treated parts, so no carbide laying around here.
Sounds like carbide is the way to go from everyone's comments, so back to the masonry vs standard bit. I found a masonry bit that is the right size and solid carbide tip pretty cheap. Would this drill cleanly enough since I am only taking off about 10 thou?
designer
Member
Solid carbide or carbide tipped twist bit will work. .005 per side is not a lot when going thru a 1/2" of cased surface. Keep coolant on it. The way I have done it is that when the bit starts cutting, keep steady pressure on it to keep it cutting to the bottom. Stopping and then restarting is "hard" to do in your "case". Sorry, couldn't resist that.
Curly
Member
The masonry bits I've seen don't have the right edge geometry and are not as sharp as ones for metal.
If you aren't doing a lot you could polish the material to size by cutting a slit in a rod and wrapping sandpaper around the rod. Cloth backed sandpaper preferred and spin it with a die grinder if you have one.
If you aren't doing a lot you could polish the material to size by cutting a slit in a rod and wrapping sandpaper around the rod. Cloth backed sandpaper preferred and spin it with a die grinder if you have one.
nativewooder
Member
Good Luck with using Masonry bits to drill steel! When I worked in the hardware business, we had many customers complain after their masonry bits fell apart when trying to drill steel, cast iron, and many other things that were not masonry. Then we pointed out the Large Sign that said "Don't use these masonry bits on anything but masonry and its' variations".
Mapster
Member
Thanks for the advice. I will either be purchasing a carbide bit to drill it out or will be moving more into the kitless realm for this pen. I appreciate all of the comments!
A masonry bit will be worthless for this.
If you are trying to open up a round bar that has been drilled -a sleeve as you mentioned earlier being what I visualize this as being- just chuck it up in a lathe, mount a dremmel on the tool post using a small grinding bit like a boring bar with the part turning slowly to grind the ID to whatever size you want.
Annealing the ID could be an option and you could do this by turning a close fitting rod to the ID and heating it red then sticking it in while cooling slowly to soften only the ID of the part. (consider that the rod will be larger when heated than when cold, and you can slow the cooling process even more to get better annealing by putting the whole thing -heated rod and part- into vermiculite or pearlite to slow the cooling even more). This should leave the hardening mostly unaffected everywhere outside of the bore if the wall thickness is fairly thick.
Or just buy a carbide drill bit or end mill, you will probably find a use for it in the future anyway.
FWIW, annealing is accomplished by heating the steel to a high temperature (red or better, depending on the steel) and cooling it as slowly as possible. I'm a little surprised to someone using 12L14 for a hardened part since it is not known for its hardenability because of the lead content.
If you are trying to open up a round bar that has been drilled -a sleeve as you mentioned earlier being what I visualize this as being- just chuck it up in a lathe, mount a dremmel on the tool post using a small grinding bit like a boring bar with the part turning slowly to grind the ID to whatever size you want.
Annealing the ID could be an option and you could do this by turning a close fitting rod to the ID and heating it red then sticking it in while cooling slowly to soften only the ID of the part. (consider that the rod will be larger when heated than when cold, and you can slow the cooling process even more to get better annealing by putting the whole thing -heated rod and part- into vermiculite or pearlite to slow the cooling even more). This should leave the hardening mostly unaffected everywhere outside of the bore if the wall thickness is fairly thick.
Or just buy a carbide drill bit or end mill, you will probably find a use for it in the future anyway.
FWIW, annealing is accomplished by heating the steel to a high temperature (red or better, depending on the steel) and cooling it as slowly as possible. I'm a little surprised to someone using 12L14 for a hardened part since it is not known for its hardenability because of the lead content.
JTisher
Member
12L14 is not that expensive, You could probably have 40 ft delivered for what a carbide drill would cost.
Joe
Joe
Mapster
Member
JTisher, it is all about making a pen from the parts I collected at work, otherwise I would definitely be buying my own steel! You are right though, one carbide bit is worth quite a bit of steel round rod!
frank123, the dremel idea is excellent! Can't believe I hadn't thought of that before! Still may end up buying a carbide bit if I can find one at a reasonable price as you say. The annealing seems like a cool process, but a bit more than I want to chew on currently. Thanks for the tips!
frank123, the dremel idea is excellent! Can't believe I hadn't thought of that before! Still may end up buying a carbide bit if I can find one at a reasonable price as you say. The annealing seems like a cool process, but a bit more than I want to chew on currently. Thanks for the tips!
Rich L
Member
Still not sure what you're doing - is it a blind hole or all the way through? Is the part round?
What I would do is bore it. If the part won't support that then use as close a carbide twist drill as you can (not a masonry bit) to get close to your final diameter. I'm not sure how you were thinking of getting to the final diameter of .334 with a drill as that size standard, exactly, doesn't exist. If you can't bore on a lathe then put a carbide fly cutter on your drill press and bore it. SFM should be about 60 and that translates to about 700+ for RPM at your diameter. If the .320 hole is already there then this should be easy but clamp your part down securely. Getting through that hardened layer will challenge you especially if you need to get through the backside layer. Maybe a picture or rough drawing of this part would help. Again, I'd highly recommend you not try a masonry bit because as far as suitability for precision metal drilling they are crap. They're not made for that kind of work.
Good luck!
Cheers,
Rich
lwalper
Member
Or just re-heat it to remove the temper
, then work it with regular HSS tools and good lubrication.
, then work it with regular HSS tools and good lubrication.