Thread Cutting; Metric Thread Cutting - Jet BD-920W Operating Instructions And Parts Manual

Thread Cutting

As indicated on the threading charts (see Figure
21), several different threads can be cut using the
proper combination of gears and settings. When
cutting inch threads, the half nut and threading dial
(Figure 19) are used to thread in a conventional
manner. The thread dial charts specifiy at which
point a thread can be entered using the threading
dial.

Metric Thread Cutting

The only difference in metric thread cutting is the
half nut must be engaged during the entire
threading process. The thread dial cannot be
utilized.
Set the machine up for the desired thread pitch
(according to the metric threading chart on the
machine, also shown in Figure 21). Start the
machine and engage the half nut. When the tool
reaches the part, it will cut the initial threading pass.
When the tool reaches the end of the cut, stop the
machine by turning the motor off and at the same
time back the tool out of the part so that it clears the
thread.
Do not disengage the half nut lever. Reverse the
motor direction to allow the cutting tool to traverse
back to the starting point. Repeat these steps until
you have obtained the desired results.
Example of Gear Set-up to Cut 10 T.P.I. (Figure
20)
1. Loosen screw (1, Figure 20).
2.
Loosen bolt (2). Remove washers (3) and gear
(6).
3.
Loosen bolt (7) to allow movement in the center
gear position.
4.
Loosen nuts (5). Remove washer (4) and gear
(8).
Re-assemble as follows:
1. Install 40-tooth gear in position (6) with
bushings, washer, and bolt.
2.
Install 32-tooth gear in position (8).
3.
The center 127-tooth gear remains in place.
4.
Adjust gear to mesh with upper and lower gear
and tighten bolt (7).
Figure 19
Figure 20
Figure 21
15