Re: [CAD_CAM_EDM_DRO] Milling Machine Taper question

Matthew King wrote:

> I've got a slightly off topic question for you folks, if ya don't mind.
>
> I've recently purchased a nice, old Milwaukee manual mill - it's got an NMTB
> 40 taper with .625-11 (5/8-11) drawbar thread. What other tapers can be
> used in this machine? Can a CAT 40 be used? It seems to have the appropriate
> taper and drawbar(actually pullstud) thread, although it's missing the
> "straight" area at the top of the taper. BT 40 seems to have the right
> taper, but a metric drawbar/pullstud thread.
>
> Mine is shaped something like this:
>
> | | <------ this is the "straight" part that isn't on
> a CAT40 taper, as far as I can tell...
> | |
> / \
> / \
> / \
> / \
> | |
> ---------------
>
> Can anyone help me out here? I need a decent collet holding chuck for this
> thing to make endmill changes easier and they seem to be far more readily
> available on the surplus market in CAT form rather than NMTB.

I don't think the straight part of the taper is so important on this one,
as the taper is pretty long, and should secure the tool quite well.
The short taper on the R-8, for instance, really needs the straight part
to resist side forces.

Most of the difference between the variants of the NMTB standard tapers
is in the V-flange used for auto tool changers. There may also be some
differences in the drive teeth, and the drawbar or retention stud thread.

You might be able to put in a thread adapter to make all the holders take
one particular drawbar.

One thing to consider, especially if you may go CNC at some time, is to
get a bunch of tool holders rather than collets. With the collets you can't
repeatably position tools. With tool holders, you can pre-measure the
tool length and store them in a table, then you don't have to 'touch off'
the tools all the time.

Jon