Fitting Change Gears For Thread Cutting; Thread Cutting With The Turning Tool; Thread Cutting Using The Top Slide - Proxxon PD 250/E Manual

Fitting change gears for thread cutting

The PROXXON Lathe PD 250/E offers You the possibillity to cut
metric threads. You find a label on the inside of the cover of the
gearbox of the machine to get the desired gear combination. The
number of teeth is imprinted on all change gears. All required
change gears are included in delivery.
The PD 250/E is supplied with installed gear arm and the change
gear combination for the automatic feed of 0.05 mm/revolution. It
is only necessary to replace the change gears installed on the gear
arm for thread cutting.
For example, if cutting a thread with a pitch of 1.0 mm, the table
on the drive gearbox will show the following data:
W 15 - gear on the main spindle with 15 teeth. This gear is already
installed on the shaft and must not be replaced.
Z 1 15 - Z 2 20 - Intermediate gear for the toothed belt of the main
spindle with15 teeth and permanently linked gear for the leadscr-
ew with 20 teeth.
L20 - leadscrew gear with 20 teeth. Of course all operations to cut
a inch system based thread are analogous to the described exam-
ple with the metric thread! Note the different units for the thread
pitch on the labels inside the gear box cover!
1. Release the clamp screw 1 (Fig. 18) and tilt the gear arm (2)
slightly upwards to remove the toothed belt (4).
2. Remove the fastening screws (3 and 5) from the normal gears
for the automatic feed.
3. Fasten the change gear "Z1-Z2" with 15/20 teeth (Fig. 19) to
the gear arm (3) using the screw (2), pulley, reduction sleeve
and nut. Please observe: The change gear "Z1-Z2" runs freely
between pulley and sleeve.The washer prevents the toothed
belt from becoming detached from the gear"Z1".
4. Do not yet tighten the fastening screw nut (2) (off-centre
adjustment must still be possible).
Note:
5. Release the set screw (1), remove the change gear "L40" and
replace with the change gear "L20".
6. Please observe: The grain of the leadscrew change "L" must
always point to the lathe chuck. The set screw (1) must be
clamped onto the flattened part of the shaft.
7. To ensure that there is sufficient play between the change
gears, always insert a strip of newspaper between the teeth
when pushing the change gears together. The thickness of the
newspaper should correspond to the required tooth play.
8. Push the axle of the change gear "Z1-Z2" onto the arm so that
it contacts the leadscrew gear "L" and then tighten the
fastening screw nut (2).
9. Position the short toothed belt for the connection between the
gears "W" and "Z1" on the main spindles.
10. Push the gear arm (3) downwards and tighten the clamp screw (4).
A useful hint:
A perfect, good-quality thread can only be cut by using the top
slide. Advancing the thread tool is performed using the cross-slide
as described above.
However, this causes the top slide to shift by 0.025 mm to the left
and the same distance to the right.
The chip in the thread is therefore always only removed from one side.
Once the full thread depth has been reached, a final full cut is
made by advancing slightly.

Thread cutting with the turning tool

Use the lowest speed when cutting threads and proceed with
utmost caution.
The automatic feed must remain switched on until completion of
the thread. Disengaging between individual steps renders further
work impossible.
Only switch over the motor switch once the lathe chuck has come
to a complete standstill. Switching over immediately increases
wear and reduces the service life of the motor.
For the following operations, the work piece must be machined
completely and have the correct thread outer diameter.
It is advisable to work out a chamfer at the beginning of the
thread. The thread turning tool must be clamped at an angle of 90°
exactly.
1. Clamp the work piece.
2. Switch off the automatic feed and set the turning tool to the
starting position.
3. Switch on the machine 2 (Fig. 20) (clockwise rotation).
4. Advance the turning tool on the cross-slide (1) and engage
feed (3).
5. Switch off the machine when the required thread length has
been reached (2).
6. Move back the turning tool slightly with the cross-slide.
7. Move the support back to the output position. To do so, switch
over the turning direction of the main spindle.
8. Advance the turning tool and repeat the steps described above
until the required thread depth is reached.

Thread cutting using the top slide

A perfect, good-quality thread can only be cut by using the top
slide (accessories).
Advancing the thread tool is performed using the cross-slide as
described above.
Important
Note:
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