turning down drill bits? cutting hss, with hss?

[1950coronet600hp]

So I need to cut down the shank of a 9/16 drill bit, going to do it on the lathe. everyone says that the shank isn't hardened so that the chuck jaws bite the drill well, and that its regular soft steel. and that makes sense. Here's where it gets muddy for me. the drill starts out as a piece of hss steel alloy, then its machined and then hardened. so, what exactly is the shank? just carbon steel? or what? is it the hardening process that makes it HSS? I can reduce the front angle of my lathe bit, as well as radius the cutting edge to help with heat transfer. but still it seems to me that the tool and the work are made of the same material, which would tell me that the work piece would dull out the tip quickly. regardless if its hardened or not. I'm not against sharpening the bit after every pass, but that would be a pain. I'm hoping that I'm overthinking this, and its easier than I think. but some input would be appreciated.

 

[Doug Arthurs]

I have turned the shank down on a bridge reamer. I was some time ago but I don't remember it being overly difficult but I am thinking I probably used a carbide insert or a brazed tool bit.

 

[astroracer]

Your HSS lathe tool will do fine, nothing special is required to turn down the shank of a drill bit. The drill is made out of HSS, it's the hardening process that makes it into a cutting tool.
Mark

 

[rsanter]

The outer skin of the Shane will be a little harder than the inside. If it gives you trouble you can take a little,off with a grinder then put it in the lathe

Bob

 

[leg17]

Often the shank is a not HSS but is a cheaper and softer material fused on.
Makes a better product all around.
You can machine it easily.
Yes, you are overthinking this. Just do it.

 

[2oolhound]

Just for the record HSS is one of four classes of Alloy Steel known as Alloy Tool Steel, a blend of iron and carbon with other elements plus hardening. So hardening doesn't make it HSS but it is part of the process. Alloy steels are designed to resist softening during tempering. This is known as red or hot hardness. Most other types of steel lose more hardness during tempering.

You should pick up some carbide tipped bits for your lathe for dealing with HSS.

 

[Astro_Pneumatic_Tools]

Real ground from solid HSS bits are not two different alloys, the shank is simply induction annealed to bring the hardness back down - aiding in the prevention of fracture.

 

[matt_i]

Im not convinced a drill bit is the exact same material as a square HSS lathe tool bit even though they are called the same thing.

There are a wide assortment of W-1 "drill rods" that match every single fractional size of drill bit, but NO "HSS blank rods" that I know of.

So by Occam's razor, I feel like its more of a water-hardened tool steel. Which makes for a good edge tool.

The difference needed with the HSS square toolbits is these generally get "pointed" like the precipice of a cliff with all the heat concentrating at the corner. The chisel edge on the drill bit has more of a line contact than a point contact, and thus I believe more area to spread the heat out.

 

[DougWil]

Im not convinced a drill bit is the exact same material as a square HSS lathe tool bit even though they are called the same thing.

There are a wide assortment of W-1 "drill rods" that match every single fractional size of drill bit, but NO "HSS blank rods" that I know of.

http://www.hssblanks.com/catalog/index.htm

http://drillblanks.com/Catalog.php

Available in M2 and M42.

 

[matt_i]

http://www.hssblanks.com/catalog/index.htm

http://drillblanks.com/Catalog.php

Thanks, I stand corrected. Never have run across those but I also never searched for them either.

 

[MShaw]

There are also many different alloys of HSS. M series are principally alloyed with Molybdenum, T series with Tungsten, The higher M series like M42 have cobalt added. Here is the list as of 1975. The book also lists each alloy and it's features and uses.

 

[pstemari]

O1 and W1 are more common for drill rod because they're cheaper and a lot easier to heat treat.

M2 and M42 require higher temperatures and better temperature control to harden and temper.

Sent from my Nexus 6 using Tapatalk

 

[MShaw]

M2 and M42 require higher temperatures and better temperature control to harden and temper.

And are best done in molten salt furnaces to avoid decarb and provide more uniform heating and quenching..