NOTE: These instructions accompany both the CNC
lathe already fitted with the locking system and the
retrofit kit for installing the lock on an existing lathe. If
you have a lathe already fitted with the system, only the
first part of the instructions regarding purpose and use
will be applicable.
The purpose of the leadscrew backlash lock
CNC machining operations require precise leadscrew
movement to producing a good part. The normal backlash
of .003" to .005" can be unacceptable in these situations and
a way was needed to reduce backlash to the .001" to .002"
range. This solution was developed for the Z-axis on the mill,
but it has been adapted here to work on the lathe as well.
Because I designed this lever to lock the column leadscrew
a couple of years ago, I never thought of it as an option that
could be used to control backlash; however, early one
morning I finally realized how to use this lock could be used
in this way, and we had a prototype working the next day and
were into production within a week. I’m also pleased to
report that the anti-backlash system can be added to every
Sherline lathe ever built!
By locking this lever against the saddle nut, it keeps the
leadscrew from turning once the headstock is positioned at
the proper height for the operation. This new lever positioning
system will allow you to position the locking lever in a
partially locked position, removing as much backlash as you
desire, and then it can be locked in that position. As wear
occurs, the position of the locking lever can be adjusted.
Using the Z-axis lock on a CNC lathe
The locking arm is clamped in the lock plate for shipping.
Loosen the SHCS that holds it and remove the plastic arm.
Insert the pin in the end of the plastic lever into the hole in
the end of the brass Z-axis locking lever from the bottom
side. Align the locking arm with the slot in the lock plate and
slip it in. Move the brass locking lever to provide the desired
amount of backlash. Tighten the thumbscrew to hold the
plastic arm in position. Do not overtighten the thumbscrew.
There is not a lot of force trying to move the arm. The arm
serves only to hold the locking lever in position once you
have adjusted it.
The brass locking lever is adjusted by hand as shown in
Figure 1, and then the positioning arm is locked in place.
Don't adjust the locking lever by moving the plastic arm
CNC Lathe Leadscrew Backlash Lock
P/N 4417Z/4417ZM
SHERLINE
PRODUCTS
INCORPORATED 1974
9/3/08
SHERLINE PRODUCTS INC.
ˆ
3235 Executive Ridge
ˆ
Vista
ˆ
California 92081-8527
ˆ
FAX: (760) 727-7857
Toll Free Order Line: (800) 541-0735
ˆ
International, Local or Tech. Assistance: (760) 727- 5857
ˆ
Internet: www.sherline.com
directly. You will have much better feel for the amount of
pressure needed by adjusting the locking lever itself, and the
plastic pin that engages the hole in the locking lever is not
designed to exert a lot of pushing/pulling force.
Installing a new saddle nut and locking lever on a CNC
mill not currently fitted with a locking lever
Sherline lathes have never been fitted with locking levers on
the leadscrew. This system was developed specifically for
use on CNC machines. The new retrofit installation kit
includes a new locking lever and a new saddle nut without
a spring loaded ball to hold it in the unlocked position. The
positive locking arm allows partial locking of the lever to
reduce backlash to a minimum. The small detent in the
locking lever that was formerly used to engage a spring-
loaded ball has been retained to indicate the side of the
locking lever that should be facing the saddle nut. (If the
locking lever should fail to lock against the saddle nut within
the available arc in the back of the mill column, check to see
if the lever has been installed backwards.) Install the new
saddle nut and lever as follows:
1. Remove the headstock and tailstock from the lathe.
LOCK PLATE
BODY
P/N 44171
ADJUSTING ARM
P/N 40173
FIGURE 1—Components of the lever locking system as
they are now installed on new Sherline CNC lathes.
10-32 x 7/8" SHCS
P/N 40740
BRASS LOCKING
LEVER P/N 44172/
44173
BRASS SADDLE NUT P/N 40174/41174
10-32 x 3/8"
SHCS
P/N 40510
