Southbend Turn-nado Gearhead Lathe w/ Dro 21" x 60" sb1046pf - Manual (Page 63)

For Machines Mfg. Since 3/11 Turn-Nado ® Gearhead Lathes
-61-
O P E R A T I O N
Thread Dial
The numbers on the thread dial are used with
the thread dial chart to show when to engage the
half nut during inch threading. The thread dial
gear must be engaged with the leadscrew for this
to work. Loosen the knurled knob on the thread
dial, pivot the dial gear toward the leadscrew
so that it properly meshes with the leadscrew
threads, then re-tighten the knob, as shown
Figure 80.
When threading, we recommend using the
slowest speed possible and avoiding deep
cuts, so you can more easily disengage the
half nut to prevent an apron crash!
Thread Dial Chart
Find the TPI (threads per inch) that you want
to cut in the left column of the thread dial chart
(see Figure 81), then reference the dial number
to the right of it. The dial numbers indicate when
to engage the half nut for a specific thread pitch.
The thread dial chart can also be found on the
front of the thread dial housing.
4,8,12,16,20,24,
28,32,36,40,44,
48,56,60,72 Any Position
In.
Non-
Numbered
Position
Numbered
Position
1,2,3,4
Position
1,3 or 2,4
Position
1 Only 2,6,10,14,
18,22,26,
30,54
3,5,7,9,
11,13,15,
19,23,27
2½,3½,4½,
7½,11½,13½
2¼,2¾,
3¼,3¾
2 7 ∕ 8
1
2 3
4
Same as
Metric
Threads
Figure 81. Thread dial chart.
Note: The thread dial is not used for metric
threading, or diametral and modular pitches.
With these, you must leave the half nut engaged
until the turning is complete.
The following examples explain how to use the
thread dial chart for inch threads.
TPI Divisible By 4
For threading a TPI that is divisible by four, use
any line on the thread dial (see Figure 82).
Figure 82. Any position on the dial for threading TPI
divisible by 4.
4,8,12,16,20,24,
28,32,36,40,44,
48,56,60,72 Any Position
TPI
Figure 80. Thread dial engaged with the leadscrew.
Dial Gear
Leadscrew
Knurled
Knob