all-thread lead screw( was Re: Linear rail & ball screw size suggestions

Hi Jay,

Doug had been the one on here that supported the 6 times longer nut
over an all-thread leadscrew.

I am building a 10 ft long bed for a drilling machine, and chose to
prototype with all-thread to prove the concept.

What I did was to take a 6 inch piece of Delrin/Nylon and tap it with
a 1/2-13 thread. I turned the OD to 3/4 for most of the body with a
1.25 shoulder. I pressed this into a pillow block bearing. (0.003"
over) This Delrin body has a 1" dia section to hold my timing gear
and 5/8 dia on each end to add a spring and thrust bearings to allow
me to keep it in the bearing if needed. For my long leadscrew, I am
turning the nut, not the screw. (another piece of advise I garnered
from this list)

Although it does not spin freely, it does spin easily. As I said, I
am still in development (just waiting for my Gecko's) but so far I
have not found any backlash. of course I have not thrown chips into
the threads yet either.

As I had mentioned before, design for the largest parts you may ever
use, I left room for a 1 inch leadscrew and anti-backlash nuts, just
for that day off in the future.

Dave

--- In CAD_CAM_EDM_DRO@y..., "J.Critchfield" <js3mc@a...> wrote:
> I'm looking for some help on sizing the linear rails for a small
gantry
> router. I have the Data-Cut plans and I will emulate much of what
is there
> but I need to size the rails and ball screws before I can continue.
The
> usable table area will be 12" x 18" and will be used to route up to
4mm
> graphite plate and G10. I have not chosen a router yet but I am
looking at
> the Roto-Zip or similar cut-out tool with 1/8" collets. My tolerence
> requirement is +- .001" or better.
>
> Thanks,
>
> Jay