Jet BD-920N - Thread Cutting Operations; Metric Thread Cutting; Gear Setup for Threading; Slip Clutch Function

Thread Cutting
As indicated on the threading charts below, several
different threads can be cut using the proper combination
of gears and settings. When cutting inch threads, the
half nut and threading dial (figures 20 and 21) are used
to thread in a conventional manner The thread dial
charts specifies 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 below). 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. (Fig 22)
According to the chart. The gear pattern should be set
up 40-80-40, (a)60-127-(b)30 Depending on the gear
pattern your currently using these instructions may vary
1 Loosen hex socket cap screw (1) with a 5mm wrench
2. Unscrew hex socket cap screw (2) Remove washer's
(3) and gear (4) Also, remove the bushing that is
located behind the gear
3. Loosen square nut (7) to allow movement in the center
gear position.
4 Loosen square nut (5) and unscrew shaft.
5. Loosen set screw on the bushing, and slide the bushing
off of the shaft.
6 Remove the gears. Place the 60-tooth gear (6) facing
out on the shaft. Follow with the 40-tooth gear.
7. Replace the bushing and tighten the set screw
8 Re-install the shaft Tighten square nut (5). Make sure
that 40-tooth gear lines up with plastic gear (8).
9 Place 30-tooth gear in position (4) Place the bushing
on the shaft and tighten with washer's (3) and socket
head cap screw (2).
10. 127-tooth gear should mesh with upper and lower
Fig. 22
gears. Tighten square nut (7).
11. You should allow for a Je backlash in the gears.
They should not be so close and so tight that they do
not spin smoothly
Slip Clutch
To avoid overloading the drive, a safety slip clutch is
fitted in the 130 rpm position. Overloading the drive
(rattling noise) means the depth of cut is too deep and
should be reduced.
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