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milling annealed tool steel

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  • milling annealed tool steel

    Let me start out by saying I am a novice when it comes to machining. I am trying to machine a 1/8" wide slot thru annealed carbon tool steel (1095) and L6 which is 1/4" thick using a bridgeport mill. I am using double fluted cobalt end mills. So far all I've done is burn up end mills. Can someone please advise what I'm doing wrong and what cutting speed I should be using, type of end mill (carbide? 2 or 4 flute?) and depth of cut I should be taking with each pass. Any advise will be much appreciated. regards-kc

  • #2
    If you're burning end mills, probably the first thing to do is slow down. I might try about 800 rpm and see how that went. As for depth, maybe 0.050"?

    When you're "burying" an end mill in a cut, 2-flute is probably the way to go. A cobalt end mill ought to be up to the job.
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    • #3
      I wouldnt mess around --- since your alrealy trashing cobalt i would go with carbide, I would also keep in mind that it could still have a case hardening to it, in this case (no pun intended) it is the one area that makes sense to go with a bigger deapth of cut, if you go light with a case hardening and try to "skin" your way through you will dwell the cutter tips on the hardend surface and wont break through, this results in lots of hardend surface area against your bit and low unit pressure, where if you go a little deaper they will break through and be into softer material.

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      • #4
        Originally posted by bladerunner
        I am using double fluted cobalt end mills. So far all I've done is burn up end mills. Can someone please advise what I'm doing wrong and what cutting speed I should be using, type of end mill (carbide? 2 or 4 flute?) and depth of cut I should be taking with each pass. Any advise will be much appreciated. regards-kc
        Machining index on ansi 1095 in the annealed state is off the scale small. After all it is a spring steel. Base rockwell hardness of annealed 1095 steel is between 44-47 use ceramic or carbide, the chips will be very blue.

        Whenever I work with spring steel grinding is the preferred method of cutting, because even in the annealed state this stuff is really hard on tools. Ever try hack-sawing a leaf spring by hand?

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        • #5
          I would question whether the material is actually annealed. Even high speed steel can be machined with ordinary cutters in the annealed state.
          .
          "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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          • #6
            Slow down.....? Feed faster?

            With a 4" cutter in horizontal mill, 30 rpm was plenty enough, and had to be that slow to stay out of trouble (using HSS, not working on 1095, but similar stuff). About 31 ft/min cutter speed.

            Assuming a 1/8 end mill, the corresponding speed would be indeed about 900 rpm.

            You probably were feeding too slow. A thou or two per tooth would correspond to between 1.8 and 3.6 in per minute feed.
            1601

            Keep eye on ball.
            Hashim Khan

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            • #7
              What color are the chips? The guys above are right, your initial cut should try to get below the skin otherwise you will burn up HSS, cobalt etc. quickly.
              I brought home a bunch of 2.5" x 2.5" x 12-16" sections of steel from work. they were scrapped out forks from the many forklifts and material handlers we have. I've slowly been making fixtures w/them. Same thing, the outer .100-.125 skin is harder than kelsey's nuts...the stuff underneath machines beautifully, not sure of the grade though.
              I bury my work

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              • #8
                Originally posted by bladerunner
                So far all I've done is burn up end mills.
                Don't know if you're prone to exaggeration or not so I'll take what you say at face value! If you are burning up end mills and making no chips then you could be running in reverse! Might you be my long last brother? Kind of mistake I'd make!
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                • #9
                  I'd try and drill out as much of the material as possible to lessen the work the end mill has to do. The L6 is bad enough but the 1095 can be a cast iron b***h. When milling I'd plunge mill every ten thou or so. Leave the milling of the slot untill as much material is wasted out as possible.
                  Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.

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                  • #10
                    good info

                    thanks to all for the replys and suggestions. i've ordered some replacement endmills (carbide) and will give it another run with all the info you all have provided. will report back soon. regards to all-kc

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