I was writing the below while dgericke was writing the above. My comments were WRT vtcnc's post. I'm not sure which of the three models dgericke's box is.
OK. That is the earliest one, for the 3/8" bed 12". Same as what came with the 101.27430 and 440.
One basic difference betweenall 12" and all 10" is that all of the 12" have a tumbler-style reversing mechanism and all 10" have a reversing gear box. So the 12" GB doesn't include a tumbler nor a means to attach it. The additional inch of height on the 12" separates what is called the Stud Gear on the 10" from the spindle and it's 32T gear. You could probably physically mount a 12" tumbler onto a 10" but the 32T/16T compound would already be meshed with the spindle gear. So that if you lifted or lowered the tumbler arm and were able to mesh the smaller FWD or REV gear with the spindle gear, the spindle would be locked.
As the QCGB occupies the same general space as the FWD-REV gearbox on the change gear 10", you can't keep it on the machine. That's most likely why the home built gear box that was recently the subject of a thread was entirely to the left of the headstock.
Another basic difference between the 10" and the 12" is that the main mounting bolts and tapped holes for whatever is there in front of the headstock are horizontal on the 12" and vertical on the 10".
On the part number subject, most 12" parts that are equivalent to similar 10" parts but which are somehow different begin with the letter "L" followed by a single digit and then a hyphen. On some of the exploded view drawings, the horizontal bar at the base of the letter "L" is very short and the character is easily mistaken for a numeral "1". I don't know who to blame other than the Draftsman who drew it. On earlier drawings where the digit may be a 2, 3, 4, or 5, this doesn't seem to be an issue. But it would be easy to read L6-1001 as 16-1001 if you didn't already know better.
Thanks again .
