Re: Sherline Auto Tool Changer

Terry,

Most fully automatic changers use a similar technique.

Tools are held in vee-shaped non locking single taper holders. There
is a retention knob at the top of the holder, which is the small end
of the vee shape. Fingers inside the spindle are designed to capture
this knob and pull it upward (often using belleville washers for
the "drawing in" force). The interior of the spindle is shaped so
that thes fingers lock in a failsafe way (as long as the retention
knob doesn't break of where it screws into the holder... Yes, it
happens).

To change tools, hydraulic or air pressure is used to compress the
belleville washers, which drops the fingers a bit, which allows them
to come out of the failsafe recess, which lets them release the
retention knob, which allows the holder to drop out (into a
waiting "transfer arm", or into the lazy susan itself.

Hope this makes sense,

Ballendo

P.S. Do a search of "CAT 40 holder", to see one of these holders


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "James Owens"
<wotisname@l...> wrote:

> Hi Peter,
>
> This is the bit I'm asking about. I'm a where how manual change

millers hold

> the tooling/holder in place. I have a Bridgeport type machine. The

question

> is how do auto-changers, when they are fully automatic, hold the

tooling in

> the spindle. I can change a tool in a few seconds but I have to be

there to

> do it. So if it is necessary for me to tighten a draw-bar why use an
> auto-changer when the tooling held in a lazy-susan would do?
>
> > The sherline tool holder simply screws into the spindle on a high
> > precision thread & shoulder. There's a 3mm hole in the tool holder
> > which allows you to locate in the holder to unscrew it. Sherline
> > claim that as the thread and location hole for the cutter shank

are

> > created without removing the piece from the machine, that the
> > accuracy is very high !
> >
> > I know that full size CNCs use a draw bar to pull the tool holder

up

> > against the taper and locate it onto a dog, but I am trying to

think

> > of a way of using the existing available stuff.
> >
> > Another way would be to make an adaptor to fit the Spindle and

then

> > make special tool holders to fit the adaptor.
>
> Regards,
>
> Terry