Re: Sherline Z-axis ballscrew feed.

Dan,

I agree that your idea has merit. I also agree with TimG that this is
all overkill.

Is this the new style nut with the little lever for locking? Thge one
that Joe M says to remove or fix in the "off" position?

Because that little lever is key to your solution. I made a little
piece of brass which held it in a semi-closed position, which
minimised the backlash...

Hope this helps,

Ballendo

P.S. If you've got the old, non- lockable style z axis nut: The
sherline thread is 3/8-20, a common thread. Making a decent nut seems
a whole lot less work, IMO. You may even be able to add your own
version of a "starwheel", like Sherline uses on the xand y...

Here's how: Start with a brass nut threaded for the leadscrew. Turn
its OD to fit, and mill or file grooves for the "star" shape. tap a 4-
40 or so hole in the flat back of the existing nut. Using a piece of
springy sheet, or music wire held by a 4-40 screw in this hole, bend
til it engages the grooves in your star nut, which is screwed into
position above the existing nut (like the new style locking lever).
Viola, A/b nut.




--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Statman Designs, LLC"
<titanium@c...> wrote:

> I have a question for the group of experts here.
>
> How difficult would it be to create a Z-axis for the Sherline

milling

> machines that used a zero-backlash ballscrew drive mechanism? I am

not

> suggesting that you retro-fit a ball-screw to an existing Z-axis.

The

> Z-axis simply bolts to the X-Y table and the spindle and motor

assembly

> simply bolt to the Z-axis.
>
> How difficult would it be to completely replace the Z-axis with a

ballscrew

> assembly and then re-mount the Sherline motor and spindle to the

new Z-axis?

>
> It seems that this would be quite a worth while upgrade for the

Sherline CNC

> system. The Z-axis is the weakest link in the ability to do

repeatable work

> on the Sherline. There is no backlash adjustment mechanism and the

spindle

> and motor do not weigh enough to always stay at the bottom of the

leadscrew

> pitch. This can, and has, resulted in large jumps of the Z-axis

downward as

> it settles to the bottom of the screw pitch.
>
> Daniel J. Statman, Statman Designs
> www.statmandesigns.com
> dan.statman@r...