Here's more, probably much more than you want, mostly from Standard B5.9. First of all the spindle diameter for each nominal size: 2" = 2 5/8", 3" = 3 5/8", 4" = 4 5/8", 5" = 5 5/8", 6" = 7 1/8", 8" = 8 7/8", 11" = 11 3/4", 15" = 15 7/8" and 20" = 21 1/2". Note these dimensions are given in inches and fractions thereof. Sizes 2" - 4" have 3 cams, sizes 5" - 20" have 6 cams. I'm not sure who is responsible for this design, it may have been a collaborative effort among the U.S. lathe builders of the day. Monarch first offered the cam lock spindle nose on its machines in 1935. I think Pratt & Whitney was also an early adaptor. (Date for Monarch's offering this is from John Legge's history of that company which can be accessed through lathes.co.uk). The first version of the Standard itself is dated 1936. The next version of the Standard, dated 1948, added the 2"and 3" type D1 sizes as well as the long taper, the Type L, series (L00, L0, L1 etc.) Note that while the 3" Type D1 wasn't included in the Standard until 1948, we know the design already existed as Monarch used this on their 10EE which came out in 1939. It's also one size smaller than what the Standard specifies for this size toolroom lathe.
So Standard B5.9 gives the spindle nose size that should be used for which size of lathe. I've never seen a 2" Type D1 spindle nose, but according to the Standard, if Myford had put a cam lock spindle nose on their Super 7, this would have been the proper size.
And "Type D1" means that it is a cam lock spindle nose. There was no "Type D2". Writers of the Standard may have wanted to leave open the possibility of later variations that would call for further division in the nomenclature There are both Type A1 and A2 (and B1 and B2) spindle noses. These are similar to the Type D1 except the chuck is secured by through bolts or cap screws in to tapped holes. These are typically used on turret lathes and now, CNC lathes.
Finally the cam lock spindle nose seems to have prevailed over the long taper. I'm not aware of any lathe currently made that uses the long taper spindle nose.
David
