View Full Version : Ground or Unground HSS Toolbits?

T Long
07-18-2003, 04:58 PM
Is there any performance difference between an unground and ground HSS toolbit?

I planned on grinding my own lathe tools; will these work correctly?

I purchased unground toolbits not knowing the diference.

Thanks in advance!

07-18-2003, 05:02 PM
The tools must be ground to the right shape with the proper angles. Have a look at this link:


And this one:


T Long
07-18-2003, 05:05 PM
Thanks for your reply!

I was referring to the actual tool blank being ground or unground.

07-18-2003, 05:10 PM
That should make no difference. Are you sure they are HSS and not carbon steel?

T Long
07-18-2003, 05:18 PM
There is no actual markings on the tools, but my receipt says "unground HSS tool bit".

07-18-2003, 05:27 PM
Unless someone mixed them up with carbon steel then they must be HSS. You will find out when you grind them. Carbon steel will start going straw color at very low temps.

07-18-2003, 05:37 PM
If by "unground" you mean such as some of the older tool bits like 'Rex', which have (mine at least) a much rougher surface finish, then I don't think it makes any difference at all. All else being equal I'd opt for the ground, because like Thrud says "shiny is good".

Les Burg
07-18-2003, 10:35 PM
Thanks for the two web sites, It helps this newbie.

07-19-2003, 01:36 AM

Happy to help.

07-19-2003, 10:41 AM
I suggest always going for the ground blanks. If for no other reason, they can be used as semi-precision spacer blocks besides being cutting tools.

BTW, do the the "mainline" makers of HSS blanks still offer them unground?

07-19-2003, 01:01 PM
I've never seen them unground.

07-21-2003, 01:47 AM
<font face="Verdana, Arial" size="2">Originally posted by Evan:
I've never seen them unground.</font>

I have, but that is large pieces supplied to the tooling industry. This plates are normally not supplied in a brite finish unless ordered blanchard ground.

"Unground" as the tool suppliers refer to it - usually refers to the lack of a cutting eedge geometry - which is left up to the user. They are ground on the four sides of the the square or rectangular bit - the two end cuts are "as cut".

07-21-2003, 10:02 AM
What's the term 'Blanchard Ground' mean, or describe. I've seen that a lot and have wondered about it. I've assumed someone named Blanchard produced the machine or process used.

Peter S
07-21-2003, 08:49 PM
I am just looking at one of my pieces of 5/16" square toolsteel - it looks like any other piece of hot rolled steel - black with scale. But it is stamped "Ultra Capital", it is a piece of HSS made by Eagle & Globe.
My guess is that it was a cheaper option to the normal ground-all-over stuff.

07-21-2003, 09:15 PM
Lynn, a Blanchard grinder is a type of surface grinder that uses a horizontal grinding wheel. They come in huge sizes( wheel diameters measured in feet) and are used to create a nice, shiny,Thrud approved surface.

07-21-2003, 09:27 PM
Ok, so as I see it, unground means the surface finish on the piece itself, not the angles of the cutting edge. If that's the case, you control the angles ground in for your cutting edges, but are left with a rough top finish, which is where the chips escape from. As Thrud has said, shiny is good, that allows for a smooth surface for the chips to slide away easily on, and you still have to grind your own angles for front and side relief. Also 60 degree points for thread cutting, and any specialty shapes for particular jobs as well. You don't get the option of top relief angles unless you grind that in, and then as you resharpen the bit, you need to keep shimming the bit to keep the cutting edge on center. Unless you have a bit holder that keeps the bit at the top relief angle, in which case you don't need to grind in the top relief, but you would want the top surface of the bit smooth anyway, and you'll have to tend to the height of the cutting edge always, as you mount and remount, and sharpen the bit. There's lots involved here, anyway, and much depends of your fixture to hold the bit.
I have also never seen an unground bit, but maybe to get some particular alloy, you'd have to accept an unground bit.