Pianotech

  • 1.  Pre threading new S&S stack screws

    Registered Piano Technician
    Posted 04-24-2017 13:53
    All-

    There was a thread or a portion of one recently that covered this in some detail and for the life of me I can't find it. There were pictures and discussion of using a Bridgeport to accomplish this, Any help appreciated. I will continue this thread with methods after more research.

    Thank you!

    David

    ------------------------------
    David Brown
    Dallas TX
    214-288-9413
    ------------------------------


  • 2.  RE: Pre threading new S&S stack screws

    Posted 04-24-2017 16:12
    1eaFnXZ6R1ySqxg9tPx1_prethread2.jpg

    unTUUYhbTUCd7f4lbn56_prethread3.jpg
    This is how I do it for my S&S rail rebuilding sub-specialty work. The tool is a threading tool. The casting available most machine suppliers, this one grizzly. To the basic casting, I had the arbor customized. The "Chuck"  is a piece of turned steel inset into the off-the-shelf arbor and brazed in. There is a 3/8 x 24 thread in that brazed in piece. The "tap" is a sample of the screw you are using, soldered to the end of a 3/8x24 threaded rod.

    Take care to center the screw before soldering. To center, clamp a piece of aluminum to drill press table. Drill a hole in the clamped aluminum the major diameter of screw threads, so the screw to be soldered fits well centered in the drilled hole. Place the screw in the hole. Chuck the threaded rod in the chuck. Lower and lock the quill, bringing the threaded rod into contact with the screw. Solder paste and 40/60  acid core solder do the trick.

    If you don't have a threading rig like this, make the tap as above, and chuck it in a straight line driver drill that lets you sight vertical and gives you the leverage to control the angle of pre-thread.  Only turn the screw in 2.5 turns. Too many turns dimples the brass on the other side of the hole, and loosens the fit of the screw in the pre-threaded hole. 2.5 turns get you a true, real nice fitting screw.


    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 3.  RE: Pre threading new S&S stack screws

    Registered Piano Technician
    Posted 04-24-2017 17:15
    Very beautiful Jim. Kind of you to respond so quickly. Thank you.

    Could one set up something like this in a drill press for a one off do you think?

    Many thanks-

    David

    ------------------------------
    David Brown
    Dallas TX
    214-288-9413
    ------------------------------



  • 4.  RE: Pre threading new S&S stack screws

    Posted 04-24-2017 17:29
    The problem with a drill press is you can not use the motor to turn the tap...you only want 2.5 slow controlled turns. You can disassemble and old cheap table top one and mess with it, but the turning of the tap is the problem.

    Another way to cheat it is to make the tap using 3/8 x 16 threaded rod. Attach the tapped rod by way of a coupling nut to a longer 3/8 rod. Drill a 3/8 hole through a large dowel to serve a bearing that you can grip. put a handle of some sort on the threaded rod to turn the gizmo and do it by eye. Or....use an old fashioned brace, and eyeball it.

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------