Re: toolpost

On Fri, 30 May 2008 10:20:37 +1000, Jordan
<jwprincic@xxxxxxxxxxxxxxx> wrote:


If one successful pair is on the front vee the result is
pretty good and it doesn't matter very much which of the two rear
vee surfaces gives the metal to metal contact needed for the side
location. This good result is because almost all the up and down
twist rigidity is provide by the two closely spaced surfaces of
the front vee - i.e.nearest the cutting forces.


Jim

Your theory assumes that the pair of vees on either one side or the
other are likely to be doing most of the holding. Wouldn't it be more
likely that either the inner or outer vee faces are making contact?
Otherwise there'd be no face contact anywhere, as one side would
interfere with the other, unless all four faces are perfect.

Jordan


Inner and outer pairs of vee face contact is possible
but, unless the errors are large, much less likely.

For this to happen the error in vee position must be so
large that, however hard the pull down force of the locking
lever, the holder cannot rotate slightly about a vertical axis to
complete the contact with the third face. The widely spaced
surfaces of inner or outer vee pairs do not act as narrow guides
and so provide little restraint to this rotation about a vertical
axis.

I think the Dixon toolpost was designed as a long life
wear resistant production tool. Precisely made twin hardened vees
that wear into full contact make a lot of sense in this context.

For less demanding applications a vee and flat
location system is much more tolerant of manufacturing errors.

Jim

.