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Carbide inserts: Please educate me

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  • Carbide inserts: Please educate me

    I must be dumb as dirt because I can't figure out which triangular inserts I need to buy for my generic lathe tool holders (They each came with an insert, and they're all worn out.)

    I've researched every Website I can find, and I'm still confused.

    I've measured the insert and can't get an exact match, although I can come close. Here are the critical numbers (as I measured them):
    • Side: .625
    • Thickness: .168
    • I.C. (by way of formula): .36 (probably should be 3/8"?)
    • Hole diameter: .135 (for 1/8" screw?)
    I think I need a TCMT3xxx or TCMW3xxx. Am I correct?

    I'm a hobbyist and I cut whatever I can find in someone's scrap pile--usually mild steel and aluminum. Because of my scrounging nature, I do lots and lots of roughing down to size.

    I just need some designations for general-purpose inserts so that I can shop around.

    Also, I have trouble finding the hole diameter in various specs. Is the approximate 1/8" diameter a standard?

    Any advice is appreciated.

    Best wishes.
    James (seatlanta)

  • #2
    Even guys who sell inserts for a living don't know it all, especially when you add in milling inserts. Not to worry about the size of the hole, though. It would seem that they're standard for the size ot the insert. It does matter if the hole is plain, for a holder where the insert is installed on a pin, and held by a clamp, or countersunk and held by a screw.

    I get my inserts from a buddy who owns a shop. I get lots of chips from his castoffs. I've got the opposite problem as you; I have to buy holders by looking at the inserts.

    I take it you have the 1/2" square shank, screw on triangle holders that come in a 5 piece set from a catalog company or the internet. The set of those I used to have used TCMT 321 inserts. It wasn't that those were the only type that would work, they were the ones that were easy to find and most reasonably priced.

    When you get into the various grades of carbide, I don't have a clue. I get mine by the pocketfull, and have no idea about the brand or grade in most cases. I do know that for my use, it doesn't seem to matter much. But then again I'm a hobby machinist, and don't need the maximum prodution that the best choice insert would provide.

    If you do have the holders that I think you do, if they're like mine they came with the cheesyest inserts of all time. Even a box of generic inserts from Enco will surprise you with the way they cut.

    Best of Luck
    I cut it off twice; it's still too short
    Oregon, USA


    • #3
      Here's a link to decipher those screwy insert codes:

      By my calculations, you'd need a TCMT322.
      Last edited by KiddZimaHater; 04-19-2009, 02:00 PM.


      • #4
        I picked up about 3 dozen TCMM-321 off Ebay for @ $.50 a piece. They have been working fine for me on my generic my insert holders. As long as I am somewhat careful, they last a long time. There are actually quite a few types of inserts that will fit your holders. The new inserts especially for those holders retail for a pretty hefty price.
        Last edited by randyjaco; 04-19-2009, 09:19 PM.
        Do yourself a favor and see if your TV carrier has America One News Network (AONN). 208 on Uverse. It is good old fashion news, unlike the networks, with no hype, bias or other BS.


        • #5
          Thanks for the advice.

          Thanks for the good advice. I ordered 10 low-cost inserts from Carbide Depot in Alabama. I bought the cheapest I could find just to make sure I had the right size.

          I ordered on Sunday evening and they arrived on my doorstep on Tuesday.

          I went to the shop, installed a couple, and they are a perfect fit. In fact, they fit better than the old ones that came with the tool holder.

          Thanks again.
          James (seatlanta)