View Full Version : Best tooling grade for interupted cut on 360 brass?

Hot Bob
03-11-2010, 06:21 PM
I'm turning some 1.750 hex using a radius tool of my own design. Well, not completely my design; more like a bunch of borrowed ideas from this board. When I made the tool I made a .375 round hole for the bit since I had no square broaches. I used a piece of HSS drill shank for my bit. Worked sweet in 6061 hex for the prototype part. It's not working so well on the 360 brass. The brass is just knocking the edge off the cutting bit. Is it likely that the drill shank is just not of high enough quality for this kind of use and a real HSS round bit should work or do I need to be using carbide?

Here's what the tool looks like. It does have a knob on the handle now.


Here's what the part looks like.


As always, I welcome any input.


03-11-2010, 06:31 PM
iam thinking that if it worked fine for the 6061 then your problem could be you need to speed up the rpms .brass is nasty for catching i run it 550 and higher , usually higher and take in very light cuts hex likes to bounce the cutter kinda like a thuding sound anyhow ,, aluim can take in deeper cuts as its more forgiving and softer then brass is,aluim can also run slower rpms as well ,

hope this helps..

03-11-2010, 06:32 PM
afaik not all drill shanks are actualy hardened HSS. I know the shanks on all my chinese drills are soft as butter, anything files them and sliping in the chuck leaves BIG gouge marks untill the shaft catchs.
I think they are held by the shanks when hardened and likey they don't bother heating the holder up enough to harden the shank..

Plus, a soft shanked drill is less likey to ruin your chuck jaws when it slips.

Try buying a real round HSS blank bit, or using the shank much closer to the flutes as the cutting edge. (a file should'nt phase it if its hardened)

PS: the square hole can be made by a file, takes a little time..
Or you can can use (a larger) mill or lathe as a shaper with basicly just a slightly sharpened HSS blank, no real profile, taking off just a mill or two at a time, but if you only need one 1/4" square hole, it will get done quick enough.
(Shaper as in, moving the quill or carriage with the spindle stoped, just using the corner of the square HSS bit as a cutting tool)

03-11-2010, 06:50 PM
you can also buy HHS round blanks for making cutters so there is no need to buy a square blank then mod you holder. other cheap option well it might be cheap take a mill thats the same od as the hole you got in there now and if its a endmill you dont need then grind that baby to shape,

you can harden the one you got in there now heat it red hot then quench it in water or air cool, it depends on the drill rod how its hardeded, some are air some are water some are oil ,, but a round HSS cutter round bar is all set just grind it and cut away..

03-11-2010, 06:52 PM
360 brass might the easiest machining metal on the planet.....but you HAVE to use zero rake tools, it will not catch if you do. That goes for drills as well. if its not cutting like butter and you're using zero rake, i'd guess its not 360...there are lots hard as nails bronzes and hard brasses that are tough to machine.

agree with the other guys, drill shanks aren't hard....get some round hss blanks

03-11-2010, 07:00 PM
Im pertty sure that HSS requires much more accurate heat treating then drill rod, hence why we all buy HSS pre heat treated (Unless your some factory with the proper ovens!). rehardening a drill bit shank is not likey to work. And you forgot the anneling stage.

Blank prehard round HSS are only a couple bucks however. (Assume its sold hardened unless stated otherwise)

Bob Ford
03-11-2010, 07:11 PM
I am sure you have lots of HSS or carbide blanks in your shop, use any broken or dull 3/8ths end mill.


Your Old Dog
03-11-2010, 07:34 PM
snap off the tip from a rat tail file after you shape it somewhat on the grinder. Maybe even a file tang. Files are heat treated in large conveyer type ovens so the tang should be as hard as the rest of the file.

03-11-2010, 08:41 PM
snap off the tip from a rat tail file after you shape it somewhat on the grinder. Maybe even a file tang. Files are heat treated in large conveyer type ovens so the tang should be as hard as the rest of the file.

maybe...they're case hardened so the inside will be softer than the outside (they are carbon steel through out, but heat treated such that outside is hard, the inside ductile). I believe they use induction heating which could work on a conveyor type system - similar to how they weld tubing

Hot Bob
03-11-2010, 09:05 PM
When I made the radius tool, I intended to buy some 3/8" round HSS but I wanted to try it out; hence the drill shank. It worked so well on the 6160 that I had procrastinated ordering the HSS. I'll get some on order tonight. The tip about zero rake is something I hadn't heard. The material should be 360. I bought it from Speedy Metals as such. Any other good brass machining tips out there?


03-11-2010, 10:33 PM

Next time you get a chance, grab any file you own WITH a tang, not a filing machine type, and see if you can bend a curlique in the tang. I'll bet you can.

They are not hardened, and if induction hardened, the tang will lie outside the hardening zone.

They are not supposed to break off the tang when in a file handle.

Ditto to the soft shank on the used drill. I'd think you can heat harden and draw the shank back, but you ain't gonna cut anything more than aluminum with a softish shank.



03-11-2010, 11:33 PM
Yeah, I'd be scared to use a file where the tang was hardened. Chances are pretty good you'd break it off and maybe damage yourself.

What's called HSS isn't always the same stuff, or the 'real' stuff. With drill bits especially, some just aren't up to it where others are. I have some long shank HSS bits from boeing surplus (years ago) that are good that will still outlive some of todays so-called HSS bits.