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Drive dogs, what's their intended purpose?

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  • #46
    Maybe this will help with some unknowns
    Tool Engineers Handbook - SME Book, 1943,1949,1959 Ref.
    Section 100
    Tapers,Spindle Noses, and Arbors
    Authors from Jones and Lamson Machine tool and lead author is Director of Engineering at Brown and Sharpe
    Is that enough credentials ?
    Table 1 -Self HOLDING TAPERS
    Lists Taper # .239 through # 1200 Total 23 variations including M T and B & S ( Jacobs and Jarno # in later Table)
    "means of driving and holding "
    All Listed as "Tang Drive with Shank held in by Friction"

    Side note on MT tapers..Sockets have two standards for depth for same size MT one without tang and the other for tang use ..
    ie MT # 2 is 2 1/2" long and with Tang slot adds 7/8"


    Edit- This book is larger (1,000+ pgs) than Machinery handbook and deals with machine design elements
    The same book was released by SME and ASTME

    last edit, clarified socket depth
    Last edited by Rich Carlstedt; 06-26-2022, 10:09 AM.
    Green Bay, WI


    • #47
      Do they say anything on steep tapers such as ISO 30, those are the tapers the original question was about.


      • #48
        Originally posted by DennisCA View Post
        Do they say anything on steep tapers such as ISO 30, those are the tapers the original question was about.
        Spindle Standards adopted 1943
        30 Taper- 3.500 taper per foot-( 16 deg 35 ' 39.4" )
        Diameter at socket gage line = 1 1/4 " -
        Length= 1 7/8 "
        Spindle Flange Dia= 2.7493 - 2.7488"
        Pilot Dia= .692-.685"
        Clearance Hole for drawbar= 21/32"
        Width of Drive Key= .6255 - .6352"
        Height of Drive Key= 5/16"
        Distance between Drive Keys= 1.315 - 1.285"
        Dia of B/C = 2.130 - 2.120"
        Bolt Threads - 3/8-16 UNC-2B
        Depth of Perfect Thread= 5/8"
        Full Depth of Arbor Hole in Spindle = 2 7/8"
        Minimum Spindle Protrusion - face to end of Column = 1/2 "
        Arbor Drawbar Thread size = 1/2-13 x 3/4" UNC-3A
        Arbor Thread size = 1/2-13 x 1" with 2" deep hole UNC-2B
        Arbor Drive Slot Width=.630-.640 "
        Green Bay, WI


        • #49
          What is the purpose of the "Pin"- "Set Screw" -"Key"-"Stop"on a R* 8 Spindle ?
          As I said earlier , it is not a drive key as it minimizes "freting" of the surface with repeated tool orientation
          BUT the reason Bridgeport put it in the spindle was to act as a stop for the tool holder or collet when the tool was installed/removed--SAFELY !
          Drraw-bar threads get buggered up, and so do threads in some arbors/collets with repeated use
          You start the draw-bar thread in the tool which is engaged with the key, now with the right hand you can tighten the Draw-bar while the left hand engages the brake on the spindle----Done
          Without a key/setscrew/stop/pin, you need to hold the tool with the left hand ( sharp edges ! ) while tightening the Draw-bar.

          How this helps those who never went through Bridgeport 101 back in apprenticeship school

          Green Bay, WI


          • #50
            I don't know if anyone mentioned it.... On cnc - it is also used for 'keying' the tool. Say you have a boring bar and you want to orient the spindle - move the axis over and pull it back out. (so you don't score up the finish you just machined) (or just so it goes into the tool chain correctly..