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QCTP holders off the saw

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  • QCTP holders off the saw

    'afternoon gang.
    I've been noticing a serious shortage of project pictures recently.. I
    gotta do all the dirty work around here?

    Nothing new but just thought I'd share some cut/welded QCTP holders.
    Making onesy twoseys on the shaper is a PITB.. don't have a dovetail
    cutter (60*).

    cold saw does a great job here, superb finish and once the angle is
    set right its pretty darn close enough for my work.

    raw stock some 1040-ish 1.5"x1.5" in the back, mild steel 3/4" x 1.5"
    in the front:

    here's the plan:

    the tails only need to be about 1/2" tall.. instead of thinning them down
    I cut away some of the body .. was going to cut some relief back there
    anyway so I was already set up:

  • #2
    The hole is for a plug weld:

    CO2 always looks like crep.

    here it is all squared up and the seat milled out

    heck it might've taken me longer to make the two height adjusters
    than it did to make 2 new holders.



    • #3
      What did you use to square them up? Surface finish looks very nice from here.


      • #4
        Just flycut on the mill.
        I can't be sure I'm square with the dovetails (ie if the tail block rotated
        a smidge while welding) -- but it seems to mount to the post fine and
        is rock solid when locked down.



        • #5
          have you made holders like this before? I would be worried about the single plug weld holding up. They aren't the easiest to get good penetration at the bottom. Even if you do, the plug weld can still twist off in that type of application.


          • #6
            Personally, I'd mill a mating slot to lock the angle vertically, as that would also take some of the torque off the weld.


            • #7

              What tool post are your holders made for? Seems like the standard around here uses those like the following image, from the CDCO web site...

              I am a bit confused by your design... doesn't seem to match what I have here...the dovetail seems reversed...

              Yours do look good! Impressive...


              • #8
                That's a holder for Sir John's QCTP design:



                • #9
                  Yes I make them and ship them to John.

                  Toolpost is an "Impero" brand. Here's a pic off the web (not mine):

                  I had the same thought about the plug weld .. I was sure to clean all
                  mating surfaces and preheated the parts a bit with a torch. In addition
                  these are for my smaller tools so I figure the load won't be as much as
                  my one-piece toolholders (which are larger, like in image above).



                  • #10
                    It may not be a bad idea to throw one together quick and sacrifice it to the vise and pipe wrench. If you can twist it off without a big ass cheater, then you should re-think the design.


                    • #11
                      Nice expedient but I think I'll continue to machine 'em from the solid.Makes sent to saw out the excess if you have a vertical saw but chomping out the dovetails ifrom solid stock sn't that ornerous a deal.
                      Last edited by Forrest Addy; 03-08-2012, 07:23 PM.


                      • #12
                        If it were me, I would, at the very least, deeply "vee" the seam between the dovetail and the block at the top and bottom (doesn't have to be milled, grinding is fine) and pile in a good hot weld there as well. That single oversized spot weld in the center just doesn't have enough support.

                        But then, you're simply trading mill time for weld time, so I suspect you're really not saving much.

                        Doc's Machine. (Probably not what you expect.)


                        • #13
                          Originally posted by bob_s
                          That's a holder for Sir John's QCTP design:

                          Just a note on this design. The drawings are dated 1994 but from memory it was in Model Engineer around 1987 so the original design was done somewhere around the 1980's, or even before ?

                          At that time the only access we had to quick change tool posts was the Dickson type as fitted to the Myford lathe, a very expensive piece of kit at the time, in fact they are cheaper 30 odd years on than they were then. We had no cheap imports and the first far eastern parts were only just coming into the country from Taiwan and quality was very suspect at the time.

                          Starting with a clean sheet of paper and knowing I only had to make one tool post but many holders I chose to use this layout as it's easier to make external dovetails than internal.

                          Mine were also made off the saw but by milling a length of material on the horizontal mill with a cutter that was vertical sided one side and 60 degree the other, the material was turned over and the other slot cut. So two passes on a decent horizontal mill got me an 18" length of pre formed holder that just required cutting and the tool slot or boring bar hole adding.

                          That particular toolpost and holders has long since gone, sold off with the Myford but the design still exists today, scaled up on my small TOS and CVA [ 10EE clone ], both posts sharing about 45 holders.

                          Would I do the same exercise today ? Probably not given the price of import holders but at the time this could not be factored in and also at that time it was still a hobby for me.

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