View Full Version : How hard is "hardened and ground" tool steel?

06-25-2008, 09:01 AM
I have decided to move forward with my 3c collet closer project and have chosen to use a 4MT to 2MT reducer sleeve as the starting point.

There are reducing sleeves available that are advertised as having a hardened tang but the balance is unhardened and ground; and then there are those that are advertised as being completely hardened and ground.

That seems pretty straight forward. However, I can buy locally such a reducing sleeve (BusyBee Tools) which they list as being hardened and ground. I have used a couple of these "hardened and ground" reducing sleeves for other projects and have found them to be hard but not too hard - that is I can scribe and centre punch and file and even cut them on the lathe with a carbide insert (never tried HSS however). When filed they seem a bit harder than annealed 4140.

My question is what is hard? It is all realitive in some respect - annealed 4140 is hard compared to 12L14 but HSS is (very) hard compared to annealed 4140.

How are hard are these (Asian import) "hardened and ground" reducing sleeves and how difficult to machine (I will need to cut to length and bore)? The locally obtained reducing sleeve seem to be soft enough to work so I am tempted but would I be better off getting one that is advertisted as being "unhardened"?

Cutting to length is easy with a cut off wheel - getting to actual dimension buy turning in the lathe at first doesn't appear to be much of as an issue as I have already proven I can do that, I am more concerned about being able to bore and finish the inner surface to take the 3C collet.

cheers, Graham in Ottawa, Canada

06-25-2008, 12:33 PM
It will vary with the innominata supplier. While experimenting with
conversion of R8 EMH to V5, some were fairly straight forward to
cut with carbide and others it just skitterred off. I fiddled with
few R8 collets of various origins, name brand and other and all of these
seemed to be relatively impervious to carbide, it would cut but
really didn't like it. A bigger lathe might speak with more authority.
I suspect internal boring would be a bear with 'hardened'
material because the small size would limit tool size and rigidity.

06-25-2008, 12:47 PM
Hardened tool steel is usually around 62 - 65 HRC -- you'll have a really hard time turning it. A file is HRC 60-61. :)


06-25-2008, 02:11 PM
CBN will cut 62-65 RC steels easily with an excellent finish. Unfortunately, edge life would probably be considered "poor" by most HSM folks, and the price per edge is cost prohibitive. Most lathes won't spin fast enough to use CBN on smaller diameter work, the edge will just break. But if you're really jonesing to cut this stuff and can afford $65-125/edge, you might want to give it a try. If the insert survives, you can use them to cut the remains of broken carbide endmills. Not much CBN won't cut.

Another option is ceramic inserts. They're far lower cost per edge considering you have 8 corners on a square insert, but they're still more expensive than your average carbide.

06-26-2008, 09:05 AM
I had a similar problem, but I needed an MT4>MT3 sleeve for my head-stock to accommodate some milling tools I have.

I bought an MT4>MT3 sleeve - complete with the slot for a drill-tang and a tapered remover.

First thing I discovered was that the MT4 taper protruded further out from my lathe spindle than I wanted.

So I used one of those great 1mm wide cut-off saws in an angle- grinder and cut off the excess at the front and the "slot" at the rear of the adaptor.

It might have been a bit short if I wanted to use it "as is" for driving a drill etc. but for location work, it was just fine - particularly if the tool (say, boring-head, ER-32 collet adaptor etc. etc.) was held in with a draw-bolt. I was careful not to over-heat or "burn" it when grinding it. I just had a large bucket of water handy. There was no detectable or visible distortion or "out of true/round".

I later saw and bought a dedicated lathe spindle MT4>MT2 reducer sleeve which was just what I wanted (but couldn't find) in the first place. It was just what I wanted.

In short (????) I'd suggest forgetting about doing any machining on the lathe - unless it is done with a tool-post grinder.

06-26-2008, 02:47 PM
Thanks for all the comments. I will take it all into account.

The "hardened and ground" reducing sleeve I currently have is not around 62 - 65 HRC as I can file it - so just how hard is it? I don't really know and is probably not so important for it's (my) use.

I will go with my gut feeling and get one of the unhardened and ground 4mt to 2mt reducing sleeves - at least with that I will be more comfortable knowing that it is supposed to be unhardened and will make working it easier.

Oldtiffie - I have cut down a reducing sleeve just as you have described for probably similar reasons (to use 3MT tooling in the 4MT headstock). Whatever gets the job done. It's always the way - modify something because you couldn't find what you wanted just to have what you where looking for suddenly appear as soon as you have finished the mods.

cheers, Graham in Ottawa Canada

06-26-2008, 03:38 PM
If its hardened without being annealed it will crack when any pressure or load is applied. Most good quality tool steels will harden to rockwell 69-70 c scale and may even crack when quenching.

06-26-2008, 04:47 PM
So lemme get this straight.....you have an item in your shop and you want *me* to tell you how hard it is from a thousand miles away:D Worse yet, there's some piece of tooling coming on a boat from China and you want me to tell you how hard it is? Order the soft one and quit worrying.

Do you need a Rockwell or other scale number? If so, go find a shop with a hardness tester or find some other things you have that are of known hardness (like glass) and do a scratch test.

One thing you don't know is whether this is tool steel or not, so answers to questions about how hard "tool steel" is (there are really lots of tool steels) may not help either. Do the file test. If it cuts easily with a file it will generally cut OK with a carbide tool. However, I would tell you that folks sometimes get carried away with this test....this is a measure of how hard the material is....tool geometry and sharpness have a lot to do with how much force is really required. In essence, there's not just the issue of how hard the work is relative to your tooling, but also how much work the lathe will have to do and how much cutting force it will see.

Then there is the other issue.....it may be machinable from a hardness perspective but may still come out looking like threaded rod when you are done because its a lousy material:D This would not be good for a collet adaptor.


06-26-2008, 08:14 PM
Thanks Paul, all good advice.

I really didn't expect anyone to tell me how hard this reducing sleeve made of "hardened and ground tool steel (of asian origin)" was. Rather I was looking for observations and comments from anyone who may have attempted such a project and used a similar object as a starting point.

In the end, I am going with my gut feeling and will get the one that is unhardened and ground to size and hope that the quality of the "tool steel" is within the limits of what I can machine well.

cheers, Graham

06-26-2008, 11:02 PM
What type of insert does your boring bar take. I have prolly five or six hundred CBN inserts and I could mail you one freebie.. And a thousand ceramic inserts of various shapes if that works better for you.. Lemme know :) JR

06-26-2008, 11:12 PM
I will go with pcarpenter. The odds of it being soft are slim to none .but you can probably cut it ,but I doubt it will be easy. I have machined rex 95 tool steel with carbide but i Do Not recommend trying it. With out a rockwell test who knows but I would put money it is between 48- 56 RC at least and any thing 42 RC are higher is a bitch to cut with out a heavy machine. If you cant turn a 1/2 inch dowell pin to 7/16 and thread it I would no try machining on a harden sleeve. Been their done that.
Just make a sleeve from scratch a LOT easer. Use a piece of 4140 pre heat treated are EDT150. Will last a life time.

J Tiers
06-26-2008, 11:41 PM
Lane is RIGHT ON.

4140 makes a dandy closer...... especially if "prehardened". Even 1020 will make one that will last you for years, by which time you will probably want to make a new one anyhow, as you may have a different machine, or see other problems with the old closer.

Personally, I think that starting with a reducer will create problems that you may not want.... starting with no ejector lip, and continuing with the machining of the "partly finished" item..... (assuming you have a 4MT spindle)

It is probably easier to make from scratch, actually.

06-27-2008, 01:22 PM
Jerry-- that's a good point...and tied nicely to your article that appears in the magazine this month. Turning of arbors is the same sort of precise operation as making a collet holder--the tolerances on the rest of your work are premised on the tolerances held in making the tooling.

I was lucky-- my lathe has an MT5 spindle and I bought the spindle nose piece that is part of a Grizzly lever closer....its MT5 to 5C and seems to run very true (less than a tenth) in my lathe spindle. Its made of cast iron best I can tell from the finish. If a guy is starting from scratch, cast iron may be a nice option...it finishes very smoothly and even has some lubricity that I think may reduce the tendancy to gall from squeezing on a hardened collet.

As has been discussed here a lot, the DuraBar and Versa-Bar products are really nice to work with...no voids no hard skin etc:

I have ordered from these folks before:


07-06-2008, 11:32 AM
Everyone who has responded has given me much to think about and consider.

Thanks JRouche for your very generous offer but I will pass.

I have decided that I will make my own adapter as it shouldn't be any more difficult that modifying something else and I will get what I want rather than a compromise. I can also choose the material from which to make it. I like the idea of 4140.

First things first however, I will need to make a bigger boring bar; the ones I have are quite small as I haven't had the need to do any boring of this diameter or depth and all my boring bars are quite small.
post and tool holders.

cheers, Graham

07-06-2008, 03:44 PM
If you're looking for a 4140 supplier:

I just had a major tool steel gloat over at the local office of www.crucibleservice.com I ended up walking out with a an 11 inch long piece of 4 inch diameter 4140 gratis. The local office has a rack of drops which they usually sell at a discount but the veteran sales guy thought any nut who's got a mill and a lathe in the back yard deserves a break so he gave me the 4140 drop and also a 24 inch drop of 2 inch diameter D2!

The current price of 4140 there is $2.70 a pound (I bought a bunch of 2 inch by 1/2 bars in addition to acquiring drops).

I don't know what other offices are like and I haven't had to deal with them by mail but they were absolutely great to do business with here in Huntsville.

I hope this helps.


07-06-2008, 05:38 PM
Cameron, that is pretty a pretty good deal.

I can get most anything I want locally which is a bit unusual for city that doesn't really have much in the way of "heavy" industry. There is a local Metal Supermarket and while their prices are reasonable they have never given me anything for free other than the occasional free cut when I have paid cash.

cheers, Graham in Ottawa Canada.