In article ,
Wayne Cook wrote:
On Tue, 28 Jun 2005 10:39:48 GMT, "DeepDiver"
wrote:

[ ... ]

One thing that's still not clear: in my Machinery Handbook, it shows that
the drawbar for NMTB tapers have two threaded portions at the toolholder
end: a larger threaded portion (what they call the "Large End"), followed by
a smaller threaded portion (what they call the "Small End"). Why is the
drawbar stepped in this fashion and how does it work with the NMTB taper
toolholder?


Because not all tool holders have the same size threads. I ran into
this on the Cinci #3 I ran at previous employment. The collection of
tool holders there was very old and some of them used the large thread
while others used the small one.

Exactly. I have both styles for my Nichols horizontal mill.

Also for the vertical or right-angle head, which has an
interesting drawbar, with a double-ended drawbar and a double-ended nut
on the end, so both are reversed to handle the other size NMTB thread.

To see photos of it in both modes, go to my web page on the
Nichols mill:

http://www2.d-and-d.com/NICHOLS-mill/index.html

click on the link for the vertical head, and go down to images

dsc02290.jpg

and

dsc02300.jpg

I keep being tempted to make a duplicate of that for the
full-length drawbar for the horizontal spindle. As it is, I have one
using the smaller thread which I received with the mill, and another
using the larger thread which I made of allthread.

I hope that this is some help,
DoN.
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