turning drill shanks

Froneck · Mar 21, 2019

I have been modifying New made in USA drills for my customer for some time, have ground Hundreds of them. Those above 1/2" as in this case 5/8" I re-ground the points but have to reduce the shank to 1/2" to fit most drill chucks. In the past I had no problem but this batch the heat treat is not quite right. I have been using AR8 in C-2 but it'd not hard enough. Called MSC and C-5 made in USA was recommended, I asked about C-6 but was told they have only Chinese, ordered them too. Chinese were junk so I tried C-5 but they too had trouble cutting but I did manage to get a few done. Ordered K21 Kennametal, tried it but I think this drll is harder yet. The older versions the shank got hard after about 1-1/4" of a 1-1/2" long cut, Some of these are hard on the end for about 1/4" get softer for 1" then harder again. Though the soft is not very soft, now that the K21 arrived the first one was only softer in about the middle of the 1-1/2" long cut for about 1/4" Anyone know of harder carbide available. I see McMaster Carr has diamond tipped tool bits, might they work? I never used diamond tool bits. Lathe is not a toy, P&W 16" Model C square head in excellent condition with CA toolpost.

Aejgx6 · Mar 21, 2019

Hit the ends of them with a induction heater. Make the harder a little less hard.

Froneck · Mar 21, 2019

These drill are HSS not carbon steel.

no704 · Mar 21, 2019

Or use a surface grinder w/collet indexer.

spaeth · Mar 21, 2019

Froneck,
If you have a torch heat the shank to almost dull
red and put them into a bucket of wood ash or dry sand
and let them cool very slowly and they should anneal
back to an easy rockwell hardness to turn. when you get
it just right the shanks should end up about 35-40 Rc
spaeth

Froneck · Mar 21, 2019

I want to cut them, I have a tool and cutter grinder and can grind them but don't want to. Too much time to do it! I have modified ball bearings using Carboloy 999 grade.

Aejgx6 · Mar 21, 2019

Froneck said:
These drill are HSS not carbon steel.

And what do you think happens to partially annealed hss? Sounds like you have the answer with your carboloy. Why did you bother asking us? Honestly the best thing to do is call you tool rep, pay some real money, and get a real solution.

PeteM · Mar 21, 2019

If it's just a deep case hard, you might try rigging up a sort of makeshift speed lathe / belt grinder combo to get below it -- then cut to size as usual. Even with two chucking steps, should be faster than trying to take them down all the way on a cutter grinder.

moonlight machine · Mar 21, 2019

Why don't you just buy them with the correct shank diameter?

Froneck · Mar 21, 2019

I do cut them, problem I'm having is the softer area cuts more that the hard so I have different sizes. The shank needs to be straight not tapered or have a belly. I have cut hard material in the past using Carboloy 999 grade, I have a few someplace but I was hoping to simply buy a few that will complete the job! This very tough one is within .005" of finished size of .500" But the extra hard areas are .010 larger! I'm simply looking for a source for Carboloy grade 999 equivalent. Maybe C-8

Milland · Mar 21, 2019

Try some CBN tipped inserts for whatever holders you have. CBN likes the steel hard, but for a small amount of soft steel cutting it shouldn't be an issue. But your lathe has to be stiff and not deflect under the load, otherwise it'll still spring forward when you get to the soft area and it'll still go undersize, though likely not as much as currently (until the tip gets damaged).

Diamond is generally recommended for non-ferrous applications, but I've used it on steels in emergencies.

jspivey · Mar 21, 2019

We hard turn a lot of D2 at the shop I work using NTK ceramic inserts. Fastenall stocks some flavors of there inserts. I’m not sure how they would react to the hard/soft/hard situation though. All I can say is they work very will in 54-60 Rc D2. Might be worth looking into. And they aren’t terribly expensive. The square inserts (can’t remember the designation of the top of my head) are around $7.00 a piece. Hopefully this helps!

Shop Supply Guru · Mar 21, 2019

moonlight machine said:
Why don't you just buy them with the correct shank diameter?

Great point. Drills up to at least 2" of the top of my head have standards shanks of 1/2". They are commonly called Silver & Deming drills.

In fact if you're doing hundreds I'd love to sell them to you!

moonlight machine · Mar 21, 2019

I have some with a 1/2 shank but I almost never use them as I have drill chucks to 1.0 dia. Anything bigger has the appropriate size taper shank for use in the drill press or lathe.

MattiJ · Mar 22, 2019

Froneck said:
I have been modifying New made in USA drills for my customer for some time, have ground Hundreds of them. Those above 1/2" as in this case 5/8" I re-ground the points but have to reduce the shank to 1/2" to fit most drill chucks. In the past I had no problem but this batch the heat treat is not quite right. I have been using AR8 in C-2 but it'd not hard enough. Called MSC and C-5 made in USA was recommended, I asked about C-6 but was told they have only Chinese, ordered them too. Chinese were junk so I tried C-5 but they too had trouble cutting but I did manage to get a few done. Ordered K21 Kennametal, tried it but I think this drll is harder yet. The older versions the shank got hard after about 1-1/4" of a 1-1/2" long cut, Some of these are hard on the end for about 1/4" get softer for 1" then harder again. Though the soft is not very soft, now that the K21 arrived the first one was only softer in about the middle of the 1-1/2" long cut for about 1/4" Anyone know of harder carbide available. I see McMaster Carr has diamond tipped tool bits, might they work? I never used diamond tool bits. Lathe is not a toy, P&W 16" Model C square head in excellent condition with CA toolpost.

K21 is some ancient grade, appears to be more on the tough side than hard, probably not good for you use.

I would try CBN inserts but that can get very expensive very fast unless you shop around ebay for bargains.
And IIRC Seco TH1000 carbide has been recommended here on PM for variety of hard-ish turning.

MattiJ · Mar 22, 2019

spaeth said:
Froneck,
If you have a torch heat the shank to almost dull
red and put them into a bucket of wood ash or dry sand
and let them cool very slowly and they should anneal
back to an easy rockwell hardness to turn. when you get
it just right the shanks should end up about 35-40 Rc
spaeth

"Almost dull red" is awfully close to maximum hardness for some HSS grades like M42.
HSS exhibits what is called "secondary hardening" where tempering at around ~400 to 550C increases the hardness.

Note that tempering at about 640C still results around HRC60 (hard as a file) that is "not so great" start for carbide. Machinable but don't expect general carbide grades to last very long.

spaeth · Mar 22, 2019

MattiJ,
You are correct. But in the back yard with a hand held
torch on a small diameter drill the almost dull red was
intended as a starting point. Almost dull to bright red
can happen quickly in that case. Also in the drawing
process the steel would cool at room temp instead of a long slow cooling in sand or ash which would produce more of an annealing affect. If those drills were any of the premium grades of HSS this may not work so well.
spaeth

Froneck · Mar 22, 2019

MattiJ said:
K21 is some ancient grade, appears to be more on the tough side than hard, probably not good for you use.

I would try CBN inserts but that can get very expensive very fast unless you shop around ebay for bargains.
And IIRC Seco TH1000 carbide has been recommended here on PM for variety of hard-ish turning.

The K21 might be the problem, The one I described was the first one I tried with K21. It was recommended by MSC. I'm not familiar with kennametal grades, C-5 was OK but struggled. McMaster has C-6 in brazed Toolbits. I'm using brazed because I can touch them up on a diamond wheel, very sharp point with a very small radius seems to work best. Note that when I say soft it's C35 to 40ish, The hard will not be touched by a new Nicholson file, not even a scratch. I have 11 of the 5/8" to complete of those I did none were the same ratio and location of hard to soft and one being soft the entire cut length.
As to the shank diameter, these are not for my use. I have all that's described including 3" drill with #5MT shank. They are for my customer, I only do as requested.

Matt_Maguire · Mar 22, 2019

K21 is a tough grade, K710 would be the C6-7 grade. For something like this maybe you can message Carbide Bob, get some small diameter hard carbide rounds & roll your own toolholder.

The 999 is C3-4, I don’t think your gonna find the old harder GE (Carboloy) grades out there, everything’s coated these days...

Good luck,
Matt

Guest · Mar 22, 2019

I would just call Kennametal customer support, they have always been helpful for me.

turning drill shanks

Titanium

Cast Iron

Titanium

Aluminum

Hot Rolled

Titanium

Cast Iron

Diamond

Diamond

Titanium

Diamond

Aluminum

Hot Rolled

Diamond

Titanium

Titanium

Hot Rolled

Titanium

Stainless

Guest

Guest

Similar threads