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PM-1228VF v3 2021-05
Copyright © 2021 Quality Machine Tools, LLC
Figure J
Final installation of scale support plate
Figure K
Indicating the scale support plate
A similar setup can be used to indicate the top surface
of the scale. The skt head saddle lock screw has been
replaced here by an M8 x 45 hex head, arrowed, acces-
sible with a standard combination wrench, inset.
were milled to size.
14. Set the exact vertical location of the scale support plate
(not the scale) by pressing down on a plate of suitable
thickness (3/8″ was used in Figure F), then tighten the
attachment screws. Why 3/8″? Because that positions the
support plate and scale well above the saddle lock nut
and gib screws.
15. Because slotted holes in the scale allow vertical adjust-
ment, the top surface of the support plate need not be
exactly parallel to the top of the cross-slide — but it will
greatly assist disassembly/reassembly if it is. Indicate it
and adjust using a setup as in Figure K.
16. Re-install the scale with M4 screws semi-tight. Re-install
the reading head with the M4 screws tight ...
but
leave the
support plate
loose enough
so it can find its own location,
up or down. Check again for front-to-back positioning.
Fine-tune the scale position if necessary.
17. Indicate the top surface of the scale as in Figure K. Ad-
just the scale up/down for an end-to-end difference of
not more than 0.010″. Indicate the side of the scale in the
same way: there should be practically no end-to-end dif-
ference if the scale support standoffs are identical — but
it is worth checking.
18. Tighten the reading head support plate screws.
19.
Install the supplied scale cover (two flat head screws).
20. Connect the reading head cable to the upper port on the
display unit. See the end of this section for parameter set-
up.
SUGGESTED PROCEDURE: LONGITUDINAL SCALE
This is a list of important points and recommendations, not a
step-by-step procedure.
In this installation the scale is stationary, attached to the bed,
and the reading head is connected to the saddle.
• Left to right placement of the scale is important. If the read-
ing head is allowed to travel beyond its designed end stop
— at either end — the scale and/or reading head will be
damaged. End stop markings are similar to those shown in
Figure G. The reading head cable should exit on the head-
stock side.
• Check the range of saddle motion before deciding where to
place the scale. At the tailstock end the saddle stops at the
point where the saddle itself (or the cross-slide DRO scale)
touches the tailstock casting: for this measurement the cast-
ing must be against its stop screw (M8 skt head screw in the
bed). At the other end the saddle is stopped by the feedshaft
clutch. For this measurement compress the clutch by rotat-
ing the outer bobbin clockwise as far as it will go (maximum
spring compression).
• Decide how the reading head will be connected to the sad-
dle. This can be done with a combination of the supplied alu-
minum angles and additional shop-made components, or a
link plate made from scratch, Figures D and M. In the exam-
ple installation, the link plate is 1/4″ aluminum, 5″ long, with
a 1/4″ thick standoff plate against the back of the saddle.
The reading head angle is 3/16″ material, slotted to match
M5 holes in the link plate, Figure P. The underside of the
angle is slotted for M4 screws (2.36” centers).
• Check that the M4 holes under the reading head are proper-
ly tapped. Run an M4 tap through them to be sure.
• The machined surface in back stands proud of the main
casting. Remove and discard the four set screws. The scale
(also the cover) needs standoffs at both ends to clear this
surface. Washers totaling about 0.2” thick were used to
standoff the scale in the example installation.
• Set the height of the scale using a block as in Figure L.
•
Drill and tap M5 for the scale ends (for precautions see the
separate lathe DRO installation note from Precision Mat-
thews).
• Install the scale temporarily. Place the cover on top of the
scale, with a little space to allow for scale adjustment. Mark
for two M5 attachment screws. Remove the scale before
drilling and tapping — cast iron dust gets everywhere.
•
Re-install the scale in its final location, indicating side and
top as Figures M and N. Spring lock washers under the M5
