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View Full Version : What's an easily machinable and hardenable steel?



beanbag
07-24-2009, 12:39 AM
Looking for a steel that is not hard to machine (no more difficult than SS) and is easy to harden, by at least some reasonable fraction of a millimeter at the surface. I'm looking to make stuff like tool holders, various other little small adapters and bits and pieces, pistons for a shock absorber, etc.

I have heard of tool steel, water and oil quenching, and 4140, but don't know a lot about how easy they are to machine, and how easy to harden. I don't have any sophisticated heating devices. Maybe I can borrow or buy a small torch or something... Oh, I also have an infrared bbq grill. I think things on top of the heating element can be made to glow red.

madman
07-24-2009, 12:58 AM
I used to make parts for dies from this material then flame harden it. It would when hardened and the torch sitting at one end moving of course continuously back and forth wouldl when heated enough ,, like a wave of water so to speak. Then all I did was move the torch forward across the material untill I got to the other end. RC 50 to 52 I think. It was hard enough for our die purposes when we didnt need a2 or d2 or vanadis 21 ect.

juergenwt
07-24-2009, 01:15 AM
O-1 for you.Tool steel, easy to harden with a torch. Cherry -red about 1475 deg. F or 800 deg. C . Quench in oil. Draw to light brown. Good machinability. Result approx. 59RC.Easy to heat treat. Holds an edge.
If you want something for a tool holder you could use a low carbon steel -leaded if yo want - for easy machining.Case harden if you like. Remember -this is not a tool steel, so don't use it for cutting, swaging etc..

Evan
07-24-2009, 01:27 AM
1040 medium carbon steel. It beats 4140 because all the plain carbon steels can be water quenched. It is also very nice to machine. I use it for all sorts of things and it will harden file hard. It's pretty brittle in that state but you can easily draw it back by colour in the kitchen oven. Just make sure it is totally free of oil first and it won't stink.

You need a way to heat it to bright red, dull red won't do. You can do it with a very simple forge made from a few fire bricks along with regular BBQ charcoal and a shop vac for a blower.

CCWKen
07-24-2009, 01:28 AM
O1 is easy to machine. W1 is a little harder but still machines well and is more forgiving during the "home shop" hardening process. I use a lot of W1 in "mill" state without hardening for many parts including rams, shafts, pistons, shaping dies, etc. O1 is softer in it's mill state and holds dimension better during heat treat but I've never seen the need for the extra buck$ over W1 for my applications. But then I don't build for NASA.

lakeside53
07-24-2009, 01:48 AM
How about 17-4? Precipitation hardening SS steel. 15-5 and 13-8 also, but I hear these are harder to machine.

Very simple process. Heat to 950F, 1050F or 1150F (depending on desired final characteristics) for 4 hours, let air cool... No drawing required; no scale. This is "hard though" - not surface.

I've machined a decent amount of 17-4 -not bad at all... haven't got around to heat treating it yet - need to finish the oven.

Easy to machine - 1144... very nice.

MTNGUN
07-24-2009, 02:22 AM
Everything you need to know about HSM heat treating in one post......

-- use W-1 whenever it will do the job. It's cheap, readily available, and easy to machine. Very large parts cannot be made with W-1 because large parts cannot be quenched quickly enough to harden all the way through. The water quench also causes more distortion and cracking compared to an oil quench or an air quench. Tip: many small W-1 parts can be quenched just fine in oil. For example, I often oil quench 1/4" dowels, 5/8" dies, etc., that are made from W-1. The oil quench works because the small parts cool rapidly enough, even in oil.

-- use O-1 whenever the part is too large for a water quench or distorts too much in a water quench (though if it distorts too much in a water quench, it'll probably distort too much in an oil quench, too). I rarely use O-1 since it costs a few cents more, is a little more difficult to machine, and still distorts noticeably. Tip: you can quench O-1 parts in water if you want to, the only draw back is more distortion and cracking.

-- use air hardening or other more exotic tool steels only when there is a darned good reason, because air hardening steels are more expensive and more difficult to machine. One reason to use air hardening would be because you don't want the part to distort, i.e., a reamer that has critical dimensions (but, even air-cooled parts may distort). Or, because the part is too large to cool off rapidly enough to fully harden with W-1/O-1. Since HSM'ers usually work with small parts, we rarely need to use air hardening steels.

-- I use 4140 for one application because it is available as a rectangular cold rolled bar and W-1/O-1 is not. Plus, 4140 is quite a bit easier to machine (in hot rolled or cold rolled state) than 0-1, in my humble opinion

-- I've yet to have a part crack in the quench. I think cracking is only a problem for very large parts or for odd shaped parts.

-- You can pretty much bet that a heat treated part will distort and the critical dimensions will change. In my experience, parts usually shrink, and long parts will become banana shaped. I.e., a 1/4" part may shrink to 0.249" or even 0.248". In theory, the slower the quenching method, the less shrinkage and distortion, but the bottom line is that you still have to allow for shrinkage and distortion. If dimensions and straightness are critical, you will probably have to finish the hardened part by grinding or polishing or lapping.

-- Furthermore, the hardened part may continue to shrink for several days. I've honed freshly hardened dies to perfection, only to find that after a few days, the ID had shrunk again. Hardening creates residual stresses, and those residual stresses can make the metal move when you don't want it to move.

To sum things up, use W-1 for small parts. For your tool holders, *IF* they need to be rectangular, and *IF* they need to be hardened, then 4140 rectangular bar would be the way to go -- but unhardened cold rold steel is perfectly acceptable for many tool holder applications.

As Evan said, the kitchen oven works great for tempering many small parts.

dp
07-24-2009, 03:30 AM
Don't know about hardening 1144 but I know it machines like a dream. Very much like 12L14. And I have a very light weight lathe.

Rusty Marlin
07-24-2009, 11:14 AM
1144 oil quenches to a file hard condition.
Super easy to machine, super easy to harden and temper.

I use it for all sorts of things. In the small parts I've hardened it held dimensions well too.

I use 4140 bar stock for QC tool holders because I can get the saw drops for free. I don't harden them.

Evan
07-24-2009, 11:22 AM
One more recommendation:

For dimensionally critical parts like punches and dies and for maximum toughness AND the ultimate in machinability of all the tool steels try some 0-6 tool steel. It machines like grey cast iron with a finish like aluminum and chips like steel. It's expensive but for small parts a little goes a long way. The reason it machines so nicely is because it has a slight excess of intermetallic carbon which acts like a lubricant much the same as lead does in leaded steel.

quasi
07-24-2009, 08:22 PM
for O-1 and W-1, when heat treating I heat until the piece is no longer magnetic, then quench. I learned this from one of Guy Lautards Beside reader books.

A.K. Boomer
07-24-2009, 09:02 PM
If you can stand it squirming a little O-1 is some good easy tool steel to work with, and keep in mind many of the deviance's in quenching are actually avoided in the way that its quenched --- anotherwords - if its a flat elongated piece don't go dunking it on "flat side first" or it will bow greatly - dip it edgewise and fast and then move fore and aft edgewise --- Like someone else stated -- 17-4 is good machining and iv heard like theve described its fairly easy to heat treat, after heat treating to H-900 it will still machine extremely well with the appropriate tooling.

wierdscience
07-24-2009, 09:51 PM
1144,1215 are free machining on the low carbon end.

For ease of heat treating it's hard to beat A-2,it's air hardening and no more difficult to machine than W-1 or O-1.

Carbon case hardening is a good skill to learn and it allows the use of common 1018 for large items like tool holders.It also doesn't require anything fancy in the way of a furnace.

http://en.wikipedia.org/wiki/Case_hardening

MTNGUN
07-25-2009, 12:35 AM
For ease of heat treating it's hard to beat A-2 ,it's air hardening and no more difficult to machine than W-1 or O-1.

Well ...... you may not notice a difference outside turning on A-2, but I detect a difference when drilling, parting, milling, or boring.

Machinability ratings based on W1 as 100% :

W1 = 100%

O1 = 90%

A2 = 85%

S7 = 70%

D2 = 65%


Machinability ratings based on 1212 as 100% :

4140 = 66%

C-1040 = 64%

65-45-12 nodular iron = 61%

C-1095 = 42% (similar alloy to W-1)

O-1 = 42%

A-2 = 42%

D-2 = 27%

17-4 Stainless = 45%

304 Stainless = 40%

More data here http://www.carbidedepot.com/formulas-machinability.htm

Machinability numbers are based on a fancy standardized test, and they don't always predict real world results. But ...... it's a starting point.

My suggestion is W-1 for small round parts, and 4140 for rectangular parts. Nothing wrong with 4140 round bar, either, it's just not as easy to come by as round W-1.

Evan
07-25-2009, 02:15 AM
You forgot one. O-6 machinability is 120%


Nothing wrong with 4140 round bar, either, it's just not as easy to come by as round W-1.


1040 is easy to find in the round since it is used for hydraulic cylinder rods and is precision ground too. It will serve anywhere 4140 will and is easier to machine and harden.

Here is an example of the machinability of 1040, one pass on my horizontal mill.

http://metalshopborealis.ca/pics3/hmillcut3.jpg

MTNGUN
07-25-2009, 11:47 AM
Thanks, Evan. O6 sounds neat, but I wouldn't know where to get it. Neither Enco nor McMaster Carr list it.

I stopped buying oil hardening rod after I discovered that small W1 parts could be successfully oil quenched.

Enco does not carry 1040, but McMaster has 1045 and it's slightly cheaper than their W1, not that McMaster's prices are the greatest for any material.

I try to simplify my inventory of drill rod because when you have W1, O1, A2, and S7 all laying in the same storage rack, they tend to get mixed up. Labels and markings have a way of wearing off or getting cut off.

Enco carries W1 and has it is on sale more often than not, plus we in the lower 48 get free shipping, making it my "go-to" round stock for hardened parts.

beanbag
08-22-2009, 10:08 PM
I ended up getting a 1/2" square of 4140 annealed. It was surprisingly hard to find O1 in 1/2" square, unless it cost $60+ for 3 ft. I got a 12 ft long stick of 4140 for $24.

For now, I plan to make lathe carbide insert tool holders out of this stick. The items are:
1) turning tool holder. I want the pocket that holds the insert to not deform, and the material under the insert to be hard/tough enough that a crash will only break the insert and not bend the holder

2) parting tool. This is the type that would hold the little "self grip" parting inserts. It consists of the 1/2" shank with a thin blade that sticks out. The blade needs to be fairly hard to hold the insert, plus I would need it to not distort or bend during the quenching.

3) boring bar: There isn't a lot of material supporting the insert, so I need this part to be pretty strong.

I looked up the properties of 4140 on matweb. Here's a brief list:

Material, Brinell hardness, Hrc, Tensile yield strength kpsi
SS 304 , 123, xx, 31
4140A, 197, (13), 60
4140 prehard, 290, 30, 140
4140 400f temper, 520, 52 , 220
4140 600f, 455, 48, 195
1000f temper, 340, 37, 161

I don't know materials science, but I'm guessing that the hardness ratings are how difficult it is to damage or scratch the surface, and the tensile yield strength is a measure of how "strong" the material is. As the strength goes up, so does the brittleness, which I think is represented by elongation at the breaking point.

Well anyway, I wanted to ask a couple of questions:

Is 4140A really that much harder than stainless? My stainless tool holder can scratch the 4140A bar.

For the above applications, what kinds of hardness or strength am I aiming for?

Since I have no heat treating equipment at the moment, would I have been better off getting 4140 pre hardened, or some other hardened steel, and machining with carbide?

Is a propane torch and a simple furnace enough to reach approx 1500f?

My oven only goes to 600f. Thus, is 48 Hrc too brittle?

How about just trying to flame harden the ends of the tool holders?

beanbag
08-22-2009, 10:45 PM
I used to make parts for dies from this material then flame harden it. It would when hardened and the torch sitting at one end moving of course continuously back and forth wouldl when heated enough ,, like a wave of water so to speak. Then all I did was move the torch forward across the material untill I got to the other end. RC 50 to 52 I think. It was hard enough for our die purposes when we didnt need a2 or d2 or vanadis 21 ect.

what type of torch?
quenched?
tempered?

MichaelP
08-23-2009, 11:06 AM
What's an acceptable for a lowly HSM procedure to harden and temper A2 tool steel? What result can be expected in such low tech approach?

lazlo
08-23-2009, 11:46 AM
boring bar: There isn't a lot of material supporting the insert, so I need this part to be pretty strong.

Keep in mind that heat treating will make the bar stronger, but not stiffer.

I use plain mild steel for a lot of my toolholders. The only advantage to hardening them is they don't get buggered by the setscrews.

Forrest Addy
08-23-2009, 01:02 PM
4140 is to me the go-to steel for any application where strength and hardenability is required that doesn't include cutting edges or surface durability. 4140 is suitable for most any application requireing high strength and moderate heat resistance.

1040 is a good substitute for 4140 and it's less expensive if a bit skimpy on the mechanical properties.

If you require cutting edges use whatever tool steel you prefer or one of the high chromium, high carbon 400 series stainless.

beanbag
08-23-2009, 07:07 PM
4140 is to me the go-to steel for any application where strength and hardenability is required that doesn't include cutting edges or surface durability. 4140 is suitable for most any application requireing high strength and moderate heat resistance.


What's your heat treat procedure?

gwilson
08-23-2009, 08:16 PM
O1 is agood all around steel if you need it to fully harden. We use automatic transmission fluid,but even grocery store vegetable oil will work fine.

To keep drilled holes near edges from cracking through,stomp the holes tightly with a flat ended punch and use fine steel wool. Old timers used to use clay,but then the insides of the holes didn't harden.

To make a good lathe tool,draw it medium brown. For a knife,a darker brown or purple. A very hard knife will not hold an edge well. The microscopic edge you can't see breaks off.

To make a tap,purple. For a spring,full blue. O1 is a bit high carbon for springs. 1070 or 1075 is better. Brownell's sells spring steel,annealed. So does Dixie Gun Works. One of the few items in their big catalog that is good.

J Tiers
08-24-2009, 01:59 AM
I don't find 4140 nice to machine..... it tends to eat HSS, and demand carbide.

However, A2 machines wonderfully, and you just can NOT get any easier to heat-treat than A2.... I agree with Wierdscience....

For toolholders, pretty much anything cheap and hardenable....... 1030, 4130, 4140, whatever..... CRS case hardened.....

MichaelP
08-24-2009, 04:51 AM
...you just can NOT get any easier to heat-treat than A2
JTears, could you please describe your hardening and tempering procedure for A2? What result is expected if they're done in typical HSM conditions?

lazlo
08-24-2009, 09:34 AM
I don't find 4140 nice to machine..... it tends to eat HSS, and demand carbide.

Agreed -- 4140 is tough to machine, especially on a hobby-class machine. Machineability rating of 66%. It work-hardens easily, so you have to run a high feed rate and take a sizable cut.

J Tiers
08-24-2009, 09:38 AM
Hardening is easy......

It's "air hardening"..... you don't need any fancy quench. So basically all you have to do is heat it to the right point, which, if you don't do any better temp testing, is a "bright orange heat", and let it cool.

It will be glass hard, and may be tempered the same as any other steel, polish a bit of it and heat evenly to the correct temper color for your purpose.

The problem with A2 is expense. I happen to have the better part of a hundred lb of it, plate, bar and rod stock, which I have picked up, most of it in its marked wrapping.... I tend to reserve it for tool and die type uses, other things work just as well for general purposes.

The A2 because it does not need to be liquid quenched, is not so likely to have quench problems like cracking and distortion due to uneven quench, which is hard to avoid in a liquid quench.

lazlo: I have found that my "hobby class" Logan has become significantly more "industrial" since I polished the flat-belt pulleys and got the delivered spindle power up by a factor of over two to 1...... Now the higher speed use of carbide is quite possible.

On that subject, 4140 pre-hardened, despite its machining problems, is my new favorite material for making tooling such as mill arbors etc. I just wish I had had the pulleys up to snuff when I made the arbors a few years ago.... I took off many cubic inches of material, and with 4140 PH it was not as much fun as it could have been if I had had the power at speed that I now do.

MichaelP
08-24-2009, 11:57 AM
Thanks, JT!

hwingo
08-24-2009, 01:45 PM
How about 17-4? Precipitation hardening SS steel. 15-5 and 13-8 also, but I hear these are harder to machine.

Very simple process. Heat to 950F, 1050F or 1150F (depending on desired final characteristics) for 4 hours, let air cool... No drawing required; no scale. This is "hard though" - not surface.

I've machined a decent amount of 17-4 -not bad at all... haven't got around to heat treating it yet - need to finish the oven.

Easy to machine - 1144... very nice.

I simply love 17-4. Easy to machine and leaves a beautiful surface. Easy to harden (as previously mentioned).

Harold

bobw53
08-24-2009, 03:16 PM
I simply love 17-4. Easy to machine and leaves a beautiful surface. Easy to harden (as previously mentioned).

Harold

Don't forget that its VERY stable in heat treat, with almost negligible shrinkage.

Evan
08-24-2009, 03:20 PM
Still can't beat O-6. It machines like hard aluminum and doesn't warp, shrink or crack.

1040 is about as easy to treat as there is and it comes up really hard. I just used some to make a rock chisel and it is holding up well.

beanbag
08-24-2009, 06:51 PM
Now that most of the materials have been discussed, let's talk about heat treat procedures that can be performed at home.

madman
08-26-2009, 10:51 AM
I had a bunch of SPS Tool Steel .Very nice material. Made two Die Makers Vices from them may Years Later (over 30 I still use them and they still have no nicks in them whatsoever even with a lot of uce and never were heat treated? Xpensive material but we used to FIND IT LAYING AROUND IN THE SHOOP. LOL

madman
08-26-2009, 10:52 AM
At home torch heat treat and it is tough enough for any project you will use. Lots avalable for next to free from shops as offcuts. Unfortunately there seems to be a big shortage of shops that are even open due to the economy .SAD INDEED