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Thread Dial
Tools Needed
Hex Wrench 5mm .............................................. 1
The numbers on the thread dial are used with the
thread dial chart to show when to engage the half
nut during inch threading. Loosen the cap screw
on the thread dial (see Figure 91), pivot the gear
teeth so they mesh with the leadscrew threads,
then retighten the cap screw.
Important: The thread dial is not used for metric
threading. For metric threading, you must leave
the half nut engaged, stop the spindle at the end
of each cut, retract the tool one full turn of the
cross slide, then run the lathe in reverse to reposi-
tion tool to the start of the threads.
Note: As a basic rule of thumb, you can always
cut any thread (other than metric or 4.75 TPI, by
starting on the number 1 of the thread dial.
Thread
Dial
Figure 91. Thread dial engaged with the
leadscrew.
When threading, we recommend using slow-
est speed possible and avoiding deep cuts,
so you are able to disengage half nut when
required and prevent an apron crash!
When the first thread cutting pass is complete,
the operator disengages the carriage from the
leadscrew using the half nut lever. The operator
returns the carriage for the next pass and re-
engages the half nut using the same thread dial
setting to resume the cut as in the previous pass.
-62-
Thread Dial Chart
Qty
The thread dial chart is located on the headstock,
as shown in Figure 92.
Find the TPI (threads per inch) that you want to cut
in the left columns (under TPI), then reference the
dial number in the right columns (under Scale).
The dial numbers indicate when to engage the
half nut for a specific thread pitch as indicated by
the thread dial chart (see Figure 93).
Cap
Screw
Thread Dial
Figure 92. Location of thread dial chart.
INDICATOR TABLE
TPI
SCALE
TPI
SCALE
4
1–8
13
1, 3
4.5
1
14
1-2-3-4
16
1–8
4.75
1
5
1, 3
18
1-2-3-4
5.5
1
19
1, 3
6
1-2-3-4
20
1–8
6.5
1
22
1-2-3-4
7
1, 3
24
1–8
8
1–8
26
1-2-3-4
9
28
1–8
1, 3
9.5
1
32
1–8
10
1-2-3-4
36
1–8
11
1, 3
38
1-2-3-4
12
1–8
40
1–8
Figure 93. Thread dial chart.
Model G0791 (Mfd. Since 9/15)
Chart
TPI
SCALE
44
1–8
48
1–8
52
1–8
56
1–8
64
1–8
72
1–8
76
1–8
80
1–8
88
1–8
96
1–8
104
1–8
112
1–8
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