Experienced machinist Question

[theoldwizard1]

I have a 3/8" battery drill that I use for "light jobs". Occasionally, I would like to be able to drill a 7/16" or 1/2" hole in light material. I have spare "jobber length" 7/16" and 1/2" bits, but the are M2 HSS.

Can these be turned down or should I just find a cheap set of 1/4" drive large diameter bits ?

 

[ItsNemo]

Need to use carbide to turn and will lose your hardening, but will probably still work.

They make 3/8" reduced shank drink bits though, that would be the route I'd go.

 

[MattT]

The shanks aren't HSS so yes they can be turned. But you'd be better off just picking up 3/8" shank S&D drills.

 

[rlitman]

The shanks aren't HSS so yes they can be turned. But you'd be better off just picking up 3/8" shank S&D drills.

HSS is the alloy, and the bits are HSS through and through.

I’ve seen bits home ground to a reduced shank. The result is generally wobbly and takes much effort. Just buy the 3/8 reduced shank bits. It’s cheaper than grinding.

 

[The Cobbler]

yes they can be turned down

 

[Bigblue&Goldie]

In my opinion you'd be better off with a step bit for light material. If you're willing to spend some money a Blair Rotabroach set is worth every penny. Big drill bits in thin metal can get ugly when they pierce through.

 

[davewo]

I've rarely encounted a drill with a hardened shank.

 

[toolchaser]

What davewo said. the tips are induction hardened, not the upper shank. That being said, reduced shank S&D are the way to go unless it's thin material then step drill like others posted

 

[bugnut]

Get a good metal cutting file and see if it will cut the drill shank. If the file will cut it then it can be reduced in size.
I prefer already reduced shank drills, Silver and Deming-jobbers length.
My most recent find is the hex shank Milwaukee SHOCKWAVE IMPACT DUTY Titanium Drill Bit Set (23-Piece) at HD for 30$, fits all my drills and allows me to use a quick change holder.

 

[lis2323]

In my opinion you'd be better off with a step bit for light material. If you're willing to spend some money a Blair Rotabroach set is worth every penny. Big drill bits in thin metal can get ugly when they pierce through.

[emoji106][emoji106]

 

[glend123]

I've turned them down for a 3/8 chuck without a problem.

 

[cmandp]

Yes you can turn them down with carbide lathe tooling. But HSS drill bits are like rlitman said they are HSS through out and through hardened.

For your purpose old wizard just buy some reduced shank drill bits. Taking a 1/8" on the 1/2" drill is probably going to take a while and not worth it unless you need it today and have a lathe and at least some brazed carbide tooling handy.

 

[rlitman]

Yes you can turn them down with carbide lathe tooling. But HSS drill bits are like rlitman said they are HSS through out and through hardened.

For your purpose old wizard just buy some reduced shank drill bits. Taking a 1/8" on the 1/2" drill is probably going to take a while and not worth it unless you need it today and have a lathe and at least some brazed carbide tooling handy.

I was just pointing out that the ALLOY is HSS through and through. The hardening is not necessarily the same throughout (nor should it be). In theory, good bits should be hardened fully to just past the base of the flutes, leaving most of the remainder of the shank is a relatively soft state (there is a visible line on most of my cobalt bits, but that gets erased with most surface finishes on other types of bits). So, it SHOULD be soft enough to file, and therefore maybe machine (with some difficulty). But aside from doing this as a one-off in a pinch, buying a set to fit your drill is so much easier. Bits with 3/8" and even 1/4" reduced shanks are easily sourced.

Oh, and for absolute correctness, there was a mention about S&D bits above. Silver & Deming is generally accepted to only refer to 1/2" reduced shank bits in a fractional set from 1/2" to 1". That doesn't apply to 3/8" shank.

 

[1MtnGoat]

I've turned down the shanks on dozens of HSS drills bits over the years. The shanks turn easily. Chuck the drill in a lathe and turn down. Do not try and grind. It will not be straight and slip/wobble in the drill chuck.

 

[Kevin54]

Have someone turn them down in a lathe. Takes just a couple of minutes each to do. I've probably done a few thousand over the years. And don't worry about close tolerances when turning them down.....you'll be chucking them into an adjustable chuck anyways.

 

[joe49]

Don't miss this opportunity to get a 1/2'' drill.

 

[cmandp]

I was just pointing out that the ALLOY is HSS through and through. The hardening is not necessarily the same throughout (nor should it be). In theory, good bits should be hardened fully to just past the base of the flutes, leaving most of the remainder of the shank is a relatively soft state (there is a visible line on most of my cobalt bits, but that gets erased with most surface finishes on other types of bits). So, it SHOULD be soft enough to file, and therefore maybe machine (with some difficulty). But aside from doing this as a one-off in a pinch, buying a set to fit your drill is so much easier. Bits with 3/8" and even 1/4" reduced shanks are easily sourced.

Oh, and for absolute correctness, there was a mention about S&D bits above. Silver & Deming is generally accepted to only refer to 1/2" reduced shank bits in a fractional set from 1/2" to 1". That doesn't apply to 3/8" shank.

Ah seems you're right rlitman. I was not sure HSS could be differentially hardened since a fairly complicated procedure from Carbon steel.

But it seems the smaller HSS drill shanks I have on my desk are hard and larger drill shanks are soft. Well softer than I file anyway, but that's still pretty hard.

 

[rlitman]

Ah seems you're right rlitman. I was not sure HSS could be differentially hardened since a fairly complicated procedure from Carbon steel...

I don't know HOW they do it, but I know that they do. My guess is that it's largely a proprietary process that heavily involves induction.

I remember one incident when drilling into something on a drill press with a 5/16" cobalt bit. The part was clamped into a vise that was not attached to the table. At some point, the bit grabbed and started spinning the vise. Not at super high RPMs, but certainly enough to be scary. Anyway, I shut the machine down after making for a safe distance. Due to the massive imbalance of the spinning vise, the bit bent to about a 30 degree angle, yet never snapped. I actually managed to straighten the bit (initially in a vise, and then hammering it on an anvil) enough to use it for woodworking, and still have it to this day. That moment really impressed upon me how a GOOD heat treat can be done.

 

[theoldwizard1]

Don't miss this opportunity to get a 1/2'' drill.

I have a 1/2" corded drill that will "break your wrist" if you are not using the assist handle. Not worth hauling it out for a 7/16" or 1/2" hole in a pine 1by.

 

[sberry]

I am with the buy a new drill crowd, having 1/2 chuck is a whole new world, your life will be improved, you will become more handsome, chicks dig it.

 

[Gogo300]

If your just drilling into pine wood, why not get the right tool and use spade drill bits?

 

[ItsNemo]

If your just drilling into pine wood, why not get the right tool and use spade drill bits?

Eww no, twist bits (or forstner for larger holes) have way better hole quality on wood than spade bits do.

Spade bits are pretty much relegated to rough drilling for framing purposes for me.

 

[alfazer]

If the chuck is removable you could swap it for a 1/2" chuck.

 

[dr_clyde]

Just get some reduced shank drills if you insist on using a 3/8" chuck.

Yes, you could turn down the shanks if you really wanted to, but it would be less hassle to just get the correct tool.

I think you would do well to get an inexpensive cordless drill with a 1/2" chuck. So many things have a 1/2" shank it just seems silly to have only a 3/8" chuck as the primary drill. A 1/2" cordless drill works just as well as a 3/8" drill on smaller drills, why wouldn't you want the extra capacity?

 

[metlmunchr]

You can buy a set of brad point 3/8 shank drills at Home Depot covering 1/8" to 1/2" by 1/64 increments for less than $20. They're carbon steel but HSS isn't required for drilling wood. Once you drill some holes in wood with a brad point you'll never want to use a standard tapered point drill again in wood.

https://www.homedepot.com/p/Profess...VCaCzCh1YbQcOEAQYBCABEgIbuPD_BwE&gclsrc=aw.ds

I'm sure Lowes or any of the box stores has something similar.

 

[tarbellb]

Emphasis Post #24 + #25

 

[sberry]

I think you would do well to get an inexpensive cordless drill with a 1/2" chuck. So many things have a 1/2" shank it just seems silly to have only a 3/8" chuck as the primary drill. A 1/2" cordless drill works just as well as a 3/8" drill on smaller drills, why wouldn't you want the extra capacity?

I think he does enough to warrant a good drill.

 

[The Cobbler]

a 1/2" drill doesn't solve his question. he has Morse taper drill bits he wants to use, and they don't fit a 1/2" chuck
he has 2 choices , turn down the MT drill bits or buy another bit . another drill is optional

 

[dr_clyde]

a 1/2" drill doesn't solve his question. he has Morse taper drill bits he wants to use, and they don't fit a 1/2" chuck
he has 2 choices , turn down the MT drill bits or buy another bit . another drill is optional

No, he wants to use M2 tool steel drills not MT2 taper shanks.

Nobody ever said anything about Morse taper.

 

[The Cobbler]

ahh, me very baddd
misread .

 

[lis2323]

ahh, me very baddd
misread .

As did I ...