Jet BDB-919 Operating Instructions And Parts Manual

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169.7 Thread CuttingAs indicated on the threading charts (see sect.15.0), several different threads can be cut using theproper combination of gears and settings. Whencutting inch threads, the half nut and threading dial(Figure 19) are used to thread in a conventionalmanner. The thread dial charts specify at whichpoint a thread can be entered using the threadingdial.9.8 Metric Thread CuttingThe only difference in metric thread cutting is thehalf nut must be engaged during the entirethreading process. The thread dial cannot be used.Set the machine up for the desired thread pitch(according to the metric threading chart on themachine, also shown in sect. 15.0). Start themachine and engage the half nut. When the toolreaches the part, it will cut the initial threading pass.When the tool reaches the end of the cut, stop themachine by turning the motor off and at the sametime back the tool out of the part so that it clears thethread.Do not disengage the half nut lever. Reverse themotor direction to allow the cutting tool to traverseback to the starting point. Repeat these steps untilyou have obtained the desired results.Example of Gear Set-up to Cut 10 T.P.I. (Figure20)1. Loosen bolt (1, Figure 20).2. Loosen bolt (2). Remove washers (3) and gear(4).3. Loosen bolt (5) to allow movement in the centergear position.4. Loosen nuts (6). Remove washer (7) and gear(8).Re-assemble as follows:1. Install 40-tooth gear in position (4) withwashers 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 gearand tighten bolt (1).Figure 19Figure 20