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What's an easily machinable and hardenable steel?

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  • What's an easily machinable and hardenable steel?

    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.
    Last edited by beanbag; 07-24-2009, 01:24 AM.

  • #2
    4140 A

    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.


    • #3
      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..
      Last edited by juergenwt; 07-25-2009, 12:05 AM.


      • #4
        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.
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        • #5
          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.


          • #6
            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.
            Last edited by lakeside53; 07-24-2009, 01:52 AM.


            • #7
              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.


              • #8
                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.


                • #9
                  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.
                  Ignorance is curable through education.


                  • #10
                    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.
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                    • #11
                      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.


                      • #12
                        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.


                        • #13
                          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.

                          I just need one more tool,just one!


                          • #14
                            Originally posted by wierdscience
                            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

                            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.


                            • #15
                              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.

                              Last edited by Evan; 07-25-2009, 02:25 AM.
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