Re: [CAD_CAM_EDM_DRO] Seeking Advice on Making a Rotary 4th Axis

Peter D. wrote:

>I `m planning on making a rotary 4th axis for my CNC mill and have a
>few questions: I already have the servo and drive so that isn't in
>question. I was trying to decide if I should start with a rotary table
>or perhaps an indexing head or super spacer. I know that the ratio of
>the turn handle on a rotary table provides more accuracy and torque
>being in the 40:1 range as apposed to the 25:1 ratio of an indexing
>head. But what I am most concerned with is the back lash and the
>holding ability. I'd like to use a 6 or 8 inch table so I can mount a
>good sized chuck to it. I was wondering what people here have done
>like this? And if any one has any links that they might think useful,
>I'd appreciate that too.
>
>

Rotary tables usually don't have a through hole or provisions to easily
mount
a chuck. Indexing heads are designed for this purpose. Many cheaper rotary
tables don't have anything like a spindle bearing, so the table has to
be locked to
the unit to keep it in place or it will wobble both axially as well as
some rotational
slop. Indexing heads usually have opposed bearings like a lathe spindle
so they
at least eliminate axial play.

Jon