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QCTP Sizing

Discussion in 'QUESTIONS & ANSWERS (Get Help Fast Here!)' started by BROCKWOOD, Jul 26, 2017.

  1. BROCKWOOD

    BROCKWOOD United States Active Member Active Member

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    Been looking for a QCTP & even read the comparison that is still under way. My little lathe / mill combo is identified as a 12" swing - which is the upper limit for an AXA sized QCTP. My limit of frustration & patience for my little lathe / mill combo is running very low. I don't want tool post holders that will not be of use when I get a real stand alone lathe. Shars finally gave me the number I needed. That number is "height of tool". After careful measurement, I bought the BXA thinking 'finally stepping up for ease of tool change.'
    AXA, BXA, CXA: If you're gonna insist on a QCTP, pick a lathe that doesn't fall on the edge of limits. If in doubt (& I had been until the 1 source) go conservative. In the end, be happy with your decision. When a real lathe does come home to me, BXA sized QCTP will be fitted & all the tool holders I collect along the way will be
    just right!
     
    Last edited: Jul 26, 2017
  2. whitmore

    whitmore United States Active Member Active Member

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    There's TWO limits, of course. The tallest tool you can mount, ought to have its top edge below the centerline
    when the holder is bottomed, as well as the shortest tool (probably 1/8" or 1/4") ought to be adjustable
    to be above the centerline when the holder is riding as high as the adjust screw can go.

    Typical AXA holder takes HSS square-shank bits up to 0.5", BXA takes 0.625", CXA takes 0.750"
    and the AXA holder (Aloris AXA-1) puts 7/16" of metal UNDER the shank that has to clear the compound height.
    AXA-2 variant puts 3/8".
    BXA holders are thicker, 1/2" or 7/16" under the tool bit.

    On my little lathe, there's 1.125" available, so a BXA with 5/8" tool is... overkill, but just barely workable.
    The same BXA holder with 3/4" steel won't generally work for me. The toolholder could come off,
    and I could clamp it to the compound with shims...

    The Aloris catalog (.pdf form) is available for download, has the dimensions of their
    products.
     
  3. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    The swing of the lathe has nothing at all to do with the issue of what tool post will fit your lathe. The only thing that matters is the distance from the lathe center (spindle center to tailstock center) to the top of the compound rest where the tool post mounts. The manufacturers have tried to simplify the choice of tool post, but they only have done buyers a disservice.
     
    gr8legs, mikey and tweinke like this.
  4. Wreck™Wreck

    Wreck™Wreck United States Active User H-M Supporter-Premium

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    I often drop the tool holder below the top of the post when holding small round tools in the V.
    Remove the thumb nuts, make a spacer and a block that fits over the height stud with a tapped hole for a set screw, bolt this down to the holder with a nut and use the set screw to control the tool holder height below the top.
    One may easily lower the tool by a considerable amount, like so.
    I suspect that someone will be along shortly to tell you that this is not a good idea, don't believe them.
    [​IMG]
     
    Last edited: Jul 27, 2017
  5. Buffalo20

    Buffalo20 United States Active Member Active Member

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    Wreck,

    I'm somewhat lost, most of my tool blocks, are either slightly above, slightly below or at the centerline of the QCTP. Am I reading your post wrong?? Or are you talking about a different type of tool post, other than an Aloris/Dorian/Phase II, type tool post??
     
  6. BROCKWOOD

    BROCKWOOD United States Active Member Active Member

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    I bought the Shars version of a BXA QCTP. Given the top edge of the insert needs to be on center with the lathe turning center & reading their height specifications for the insert tool, I bought it (confident in my measurements & knowing what insert holders I would be using). Not sure where my math went wrong - blatant misunderstanding by a newb (me) will ultimately be the cause of this opportunity to help others avoid the same mistake. Yes, I want a real Lathe: No, those tools & holders don't play well with a Grizzly G0773. I'll make it fit, just gotta keep whittling away at the tool blocks (holders) themselves. My QCTP is sitting flush on the compound slide in the pic below. Much easier than I thought - just change the mount thread of the center bolt to match the mount hole on the compound slide. I have my boring bar tool block dialed in! Slowly getting the other tool blocks dialed in because the bottom of the tool blocks rest on the compound slide (bottom out).

    20170707_201342360.jpg
    I thank you all for input & encourage more = always!
     

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