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A Steel that didn't like carbide, and confused me.

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  • A Steel that didn't like carbide, and confused me.

    So I've been doing a bit of airgun-smithing lately. The other day I needed to turn down an airgun barrel in diameter. Using a Borite TPG insert tool I had a heck of a time. Nasty bur that rolled up in a ring at the cut, lots of pressure needed, terrible finish. I assumed it was the steel, but several people said they had no problem. So I tried a HSS tool and found it cut freely.

    Now I was a bit confused, so I did a test and found with the exact same insert and setup that Hot rolled, Cold Rolled 1018, even 316 stainless all cut well with the carbide insert, yet the barrel steel didn't.

    Are there certain alloys that just don't respond well to carbide but do with HSS? Is it possible that the stresses introduced into the barrel somehow effected the steel in a way that it didn't respond well to the mechanics of cutting with a TPG carbide insert?

    Nick
    Largest resource on the web for Taig lathes and milling machines, www.cartertools.com

  • #2
    iam an airgun smith if yu like the sound of the title , any how carbide does not do well on airgun barrels at all as you have noticed and Hss does pretty good, the steel in the airguns barrels is not much better then a barbell bar. i do alot of custom work on airguns mod parts repairs and so on ,, iam not really sure what they use for steels or the tempers on them but there not to great thats for sure... also for speed i try not to go past 300 rpm when turnning down barrels and really light cuts to other wise its a mess and its really easy to cut to much at a time die to it being in my opnion to soft of steel.. anyhow airgun stuff is a blast have fun with it , i know i do

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    • #3
      The flat geometry of the TPG insert may have been causing problems with this alloy.

      I use lathe tooling that takes the CCMT insert, its a much more modern design with a highly positive cutting edge. Its also has a wide variety of insert types available, ranging from very sharp ones for AL to very tough ones for SS and steel alloys.

      I get my inserts from www.carbidedepot.com and I like the Hertel brand holders J+L industrial sells, the Hertel holders are the same as the ones Kennemetal sells. I use the SCLCR version, with the 80 degree CCMT insert it allows turning and facing from the same toolholder position, so its a cheap way to get started with CCMT inserts.

      It might require trying some different insert types, but I suspect you could find one that would give you as good of results as you got with your HSS tooling.

      Paul T.

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      • #4
        How many times faster than the HSS were you running the carbide?
        I had problems when first using carbide because I couldn't grasp just how fast you should run it,
        Nick

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        • #5
          I’ve had similar problems with CR

          Big thick HSS seems to work best

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          • #6
            Thanks airsmith, that confirms that it's not entirely my fault...next barrel will get treated as you say.

            I was running at the 2nd to top speed on the SB 10K, and tried it running the highest speed as well. As I said, I had no problems with other steels, just the barrel steel. I could see trying another insert, but I'll probably just stick to HSS next time I do one.
            Largest resource on the web for Taig lathes and milling machines, www.cartertools.com

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