Drive dogs, what's their intended purpose?

[Rich Carlstedt]

Maybe this will help with some unknowns
Source
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"

Rich

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
https://www.ebay.com/itm/14431270124....c101113.m2108

last edit, clarified socket depth

[DennisCA]

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

[Rich Carlstedt]

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 "

[Rich Carlstedt]

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

Rich

[skunkworks]

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..