Re: grizzly mini mill Z axis

German

I've got mine that way on a 8689 with the dovetail way. I don't know my
login (I started with onelist long ago) so I can't see those pics.

I used the Thompson 5/8 screw from McMaster. In order to make it fit, I
removed the rack gear and widened the slot that it sat in so that the
square ballnut would have room to move. Then I milled away some of the
web at the top, middle, and bottom of the z slide to make room for the
screw.

I made a wedged top bearing bracket and motor mount out of aluminum that
would slide into the column and press agains the sides. The bearings are
a pair of trailer wheel bearings in a turned tube that is locktited into
the bracket. A center shoulder keeps the races apart. I made a separate
spindle with thread to tension the bearings, provide a shaft for the belt
pulley and a bore to slide the ball screw into.

I turned the ball screw end down to just under 1/2 in a single pass.
The heardening broke away easily. This made a rather rough turn that I
locktited into the spindle with about 0.0005 clearance. I made a small
dimple in the center of the other end You do need to be careful when you
chuck or collet on this screw because the center of the thread is not
always the center of the ridge between threads.

I pressed the screw into the spindle by chucking the spindle into a lathe
collet and pushing with the tailstock. I've crashed the screws several
times to test how well the locktite would hold. I have not been able to
break either the bearing sleeve or the ball screw loose.

Ray

>    From: "g_f_bravo_g <factor@...>" <factor@...>

> In the Files link of this group have some photograph named grizzly
> cnc4.jpg with ballscrew located in the middle of the head between
> the motor and the column.
>
> Somebody have more information about this modification or know which
> is the person who make this implementation.
>
> Thanks
>
> German