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CXA or CA Tool Post?

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  • CXA or CA Tool Post?

    We have an old 17" South Bend "Turnado" lathe at work, and my primary user of the tool has been struggling with the old light post tool holder (and rightfully so). We do not do a lot of work on the machine as we contract with an outside machine shop for large or repetitive jobs. However, it is nice to be able to tweak a bushing or make a pin or two when we're in a bind. So I doubt if I'll spend an exorbitant amount on a QC tool post.

    But I need to find out first if a CXA size will suffice, or must I go to a CA tool post? McMaster Carr lists an overlap of our machine in sizes; CXA size for 13-18" machines and 14-20" for the CA. Our 17" falls right between both.

    I'll probably look for a Chinese kit to start. I can do this under the radar if around a grand or so. Then if the guy likes it and we start doing more in-house work, I can justify an upgrade with corporate.

    CXA or CA?
    Words of wisdom?

  • #2
    The one that fits is based on the distance between the center height of the lathe's chuck and the plinth that the post will be mounted on. The size of the tool holder will determine how low the cutting edge of the tool can go. The height of the tool post will determine how high the cutting edge will be.

    So... measure from the top of the compound to the center height. We'll call that H. Then look up the CA and CXA tool holders to see what size tool shanks they call for. Add the shank to the size of the bottom shelf of the tool holder to get the minimum height above the compound which we will call TH. If TH is greater than or equal to H, it's too big.

    Some people shave off the bottom of the holder to allow a bigger shank to be used in a holder that's too big. Not sure why. Keep in mind that you can go down to a smaller shank too.

    Dan
    At the end of the project, there is a profound difference between spare parts and left over parts.

    Location: SF East Bay.

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    • #3
      Dan is 100% right.
      And the swing of a lathe has nothing to do with which
      toolpost should be used. Funny indeed that they rate
      the toolposts this way. Must be marketing nutpicks at
      work.

      -Doozer
      DZER

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      • #4
        I have a 17 inch lathe... and have both CXA and CA tools and posts. Both work fine. I like the CA big tools and rigidity for heavy work.

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        • #5
          I didnt read all your long winded writers. CXA. JR

          A, the CA is the big boy. Usually crusty with grease. CA and CXA are not the same.

          CA is larger I think.
          Last edited by JRouche; 03-24-2018, 03:03 AM.

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          • #6
            As Dan says, the compound to Cl dimension of your machine is critical and it isn't always intuitive. An oversize toolpost will cause you fits and grief, as you'll be butchering and thinning holders to get them lower.

            I know the lure of the CA - it will take 1" holders, where CXA is only 3/4". You can buy extra large holders, with a larger slot. Fwiw, the shars website has some nice diagrams of most of the dimensions. CA holders will be a bit more expensive and usually more scarce.

            An undersize toolpost can always be spaced higher to reach the Cl. For small projects, you would do well to slide in an AXA with a spacer block. That is especially true if you go with a CA.


            DA tp with a quarter for freakish scale. It is close to the size of a gallon paint can, and definitely a 'two hander' to move.

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            • #7
              My CA is Dorian like the above. it's a 2-hander also!

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              • #8
                O.K., with my "H" dimension of 2.125 from top of compound to center of spindle, all research points to a CA sized tool post. Now I'm looking for enough of a "kit" to get my guy started well. Again, I'm not in a position yet to go for Aloris or Phase II tools. That said, recommendation or experience of the best Chinese bang for the buck?

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                • #9
                  17" Turnado I've used had the CA toolpost.

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                  • #10
                    Ok get out the fire hoses and extinguishers but for seldom using of the lathe I'd look into CDCO.com it's chinese but I've had no trouble with mine, plus you might save some money so you can buy some tooling.

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                    • #11
                      Just avoid the piston style from anyone, get a wedge style. They don't repeat well and once you learn how to use one of these toolposts you'll appreciate you can cut duplicates with multiple tools to size very quickly when they repeat well.

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