High Speed Steel

[theoldwizard1]

From Wikipedia on High Speed Steel

M2 is molybdenum based high-speed steel in tungsten–molybdenum series. The carbides in it are small and evenly distributed. It has high wear resistance. After heat treatment, its hardness is the same as T1, but its bending strength can reach 4700 MPa, and its toughness and thermo-plasticity are higher than T1 by 50%. It is usually used to manufacture a variety of tools, such as drill bits, taps and reamers. Its decarburization sensitivity is a little bit high.[9]

M36 is similar to M2, but with 8% cobalt added. The addition of cobalt increases heat resistance. M36 is also known as HSSE or HSS-E.

M42 is a molybdenum-series high-speed steel alloy with an additional 8% cobalt. It is widely used in metal manufacturing because of its superior red-hardness as compared to more conventional high-speed steels, allowing for shorter cycle times in production environments due to higher cutting speeds or from the increase in time between tool changes. M42 is also less prone to chipping when used for interrupted cuts and costs less when compared to the same tool made of carbide. Tools made from cobalt-bearing high speed steels can often be identified by the letters HSS-Co.

When tools are advertised as HSS, I should assume they are using M2 grade HSS, correct ?

When tools are advertised as "cobalt", unless they specifically say M42, I should assume they are M36, correct ?

 

[JimDawson]

The most common grades are M2 and M42. I have not seen T1, M7, or M36 advertised at all. Normally cobalt tools will be advertised as M42-cobalt. Unless otherwise stated, I think it would be safe to assume that just about any HHS would be M2.

 

[DMS]

Just because they say "cobalt" doesn't mean they are M42. Check the cobalt content to see what it matches. I have never seen T1 sold, but LMS does sell T15. I purchased a couple pieces. I can say that that stuff is TOUGH. The more exotic stuff (with high cobalt or tungsten content) take a lot longer to grind, but they stay sharp longer. If you are just learning, I would get some plain Jane HSS to practice on. You can also practice on regular cold rolled square stock. You won't be able to cut with it, but it grinds fast and is cheap, letting you develop your technique more easily.

Another reason to stick with plain HSS is that the cobalt content can cause something called "hard metal disease" if you breath in the dust. Best to wear a respirator/add a dust extractor if you are grinding cobalt.

 

[theoldwizard1]

Just because they say "cobalt" doesn't mean they are M42. Check the cobalt content to see what it matches. I have never seen T1 sold, but LMS does sell T15. I purchased a couple pieces. I can say that that stuff is TOUGH. The more exotic stuff (with high cobalt or tungsten content) take a lot longer to grind, but they stay sharp longer. If you are just learning, I would get some plain Jane HSS to practice on. You can also practice on regular cold rolled square stock. You won't be able to cut with it, but it grinds fast and is cheap, letting you develop your technique more easily.

I am a long way from grinding any tooling !

I am just trying to understand the lingo and when bying drills, etc. know what is my "best bang for the buck" !

- - - Updated - - -

The most common grades are M2 and M42. I have not seen T1, M7, or M36 advertised at all. Normally cobalt tools will be advertised as M42-cobalt. Unless otherwise stated, I think it would be safe to assume that just about any HHS would be M2.

Thanks for your response.

My gut says, any imported tooling that just says "cobalt" is M36 or something with unknown composition.

 

[John Hasler]

I am a long way from grinding any tooling !

Why? It isn't that hard. Have at it.

 

[DMS]

I would recommend MrPete's video on general tool bit grinding; very helpful if you haven't done it before. As far as drills, I would stick with general HSS bits. If you have the cash, but the name brand stuff from a machine tool supplier. The "name brand" stuff you see at the hardware store is not much better than the no-name stuff. It works fine for wood, but not so well in steel.

Cobalt bits are intended for harder steel. They are usually ground with a different point angle, which makes them harder to start. Unless you are going to be doing a lot of drilling in hard materials, the cobalt drills are not work the price IMO.

The best case would be to grab a cheap set from say, Harbor Freight, to use for rough work, and a nice set to use on steel and tougher stuff. I also recommend that nice set be a set of screw machine bits like this

http://littlemachineshop.com/products/product_view.php?ProductID=2827&category=-456343308

The shorter bits wander less, and take up less of your travel, which is nice on smaller machines.

 

[dulltool17]

+1 on what John said!

Get some HSS and have at it. I thought I'd forgotten how to sharpen, but it all came right back to me.

And HSS sharpening proficiency will serve you very well when you need special shapes- you'll know what to do if you practice..

Doug