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How would you line up QCTP b/bar holder with lathe centerline?

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  • How would you line up QCTP b/bar holder with lathe centerline?

    Been working with various tool holders for my ORAC CNC lathe retrofit and want to use an ER16 5/8" straight shank collet chuck for drills & reamers in a QC boring bar holder .

    Obviously the centerline of the holder needs to line up with the spindle center but the few things I've tried haven't worked well. Tomorrow after work I'll try putting a coaxial indicator in the chuck with a long finger and try to dial in at the front and the back of the hole with the bushing removed. Gonna be quite a fiddle-fest most likely. Anybody got a brilliantly simple method?

    I have a very accurate homing switch setup so once the thing is aligned, I can lock down the height adjustment and the QCTP mount nut and be pretty confident that drills will be on center every time I need one.

    Milton

    "Accuracy is the sum total of your compensating mistakes."

    "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

  • #2
    Am I missing something? Just like any lathe tool adjust operation there are many ways. Like... make a face cut and adjust for zero nub. Or, use a thin ruler and adjust for vertical when it's trapped between the work and the tooling tip.

    If you are trying to find center of your tool wrt the work, first make sure the tool post is dead square to the work (use the facing cut as a reference or a dti along the tool), then adjust the vertical (like above) the use a DTI held in a collet to find center. Same idea as aligning your tailstock
    Last edited by lakeside53; 02-15-2013, 09:04 PM.

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    • #3
      Put a chunk of scrap bar in the chuck and turn it to the proper size to fit the boring bar holder, then with the holder on the tool post ,but not locked down run the boring bar holder onto the stub and adjust the height accordingly.
      Steve

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      • #4
        I made a height gage that sits on the ways to provide a convenient stop at center height. I wonder if you will find, though, that you want the same height setting of the holder for different bits. Depending on the material I am cutting and the cutter tip, I might set center of the bar lower and rotate the cutter to provide a 17 deg. back rake or I might set it above center a bit and rotate the bit accordingly to yield a negative rake. The only part of the boring tool that should be on dead center is the cutting edge itself, hence, the height gage.

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        • #5
          I think you are on the right track with the indicator idea.

          For one thing it will tell you about parallelism vertically, which may not be well controlled with the carriage/cross slide/compound rest/toolpost combination.

          Dave

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          • #6
            I didn't realize that the Bbar went straight in. I always thought it was to be angled a bit.
            If you have the room. For the ones that I don't have room (to angle) .. I leave the big nut on the
            QCTP loose so that the who thing swivels .. then .. I just kind of dial the Bbar into the hole.
            John Titor, when are you.

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            • #7
              If it was me, i would turn a piece of stock to fit in the biggest ER16 collet, put the stock in the collet having it hang out what ever average lenth drill and reams i would be using and then indicate that at the "cutting tip" of the stock.
              ~ What was once an Opinion, became a Fact, to be later proven Wrong ~
              http://site.thisisjusthowidoit.com
              https://www.youtube.com/user/thisisjusthowidoit

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              • #8
                Since you are trying to get the boring bar holder completely aligned with the axix of the lathe you will have to make sure it is centered (a wiggler or DTI mounted in the chuck will do that) and then you have to ensure that the bore of the holder is also paralllel both horizontally and vertically.


                I'd be tempted to use a DRI mounted in the chuck using a long reach finger. You can move the cross-slide and the holder till it's in the right position. Then move the saddle to-from the chuck to make sure the reading does not change.


                Sounds like a lot of work.

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

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                • #9
                  DTI to test linear truth. Pull out a bit more of your .625 shank, or verify plane to QC block.

                  Then sweep to be coaxial. Or make a stub with a wider face and tram it.

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                  • #10
                    Why does it have to be strait with the spindle?

                    Normally when I am boring something there is already a hole in the part. I stick the boring bar in the hole QCTP deep (lol) and make sure the BB doesn't make contact with the part anywhere, good enough for me and start turning.
                    Andy

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                    • #11
                      Lots of food for thought, thanks gentlemen.


                      Originally posted by Carm View Post
                      Or make a stub with a wider face and tram it.
                      Thanks Carm, I'm liking that idea as I've been wanting to make one for my other lathe to get the QCTP squared up faster. I think I'll make 2, one with a 3/4" shank to fit my best collet and another sized to slide into the b/b block with the sleeve removed. Should be easy to get the 2 faces lined up and then tweak with the ind. Much shorter fiddle-fest!

                      (Crap, off to the salt mines, I hate working saturdays!)
                      Milton

                      "Accuracy is the sum total of your compensating mistakes."

                      "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

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                      • #12
                        Originally posted by vpt View Post
                        Why does it have to be strait with the spindle?
                        That collet set-up makes for very handy drilling, often better than the T/S.
                        Mebbe I should say "always".

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                        • #13
                          I use a dead center in the spindle or the tailstock to center any cutters in the lathe. It has to be a sharp pointed dead center to work and you need a magnifying glass to be accurate.
                          It's only ink and paper

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                          • #14
                            Well, I finally got around to doing something with the QCTP alignment issue. I turned up 2 7075 aluminum discs with steel shafts to fit a collet in the spindle and the boring bar holder. The discs were a tight fit on the shafts and I finish turned them once pressed together. It worked real well and a little juggling with a feeler gauge and a parallel had it in very good alignment drilling spot on.

                            Once it was aligned properly, I locked the adjustment down on the toolholder and added it’s location to Mach3’s tool table. Now I can call it up at any time and drill or ream away knowing it’s in good alignment.





                            Last edited by DICKEYBIRD; 03-24-2013, 09:05 PM.
                            Milton

                            "Accuracy is the sum total of your compensating mistakes."

                            "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

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                            • #15
                              Milton,
                              Is the toolpost pegged to the cross slide for repeatability ?
                              .

                              Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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