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5.
Chasers
5.1. Tasks
Figure 4: Chaser first cuts long, middle, short
You should choose the chasers according to the size of the chasers (compatible to the
chaser holder), the designated lead, the material and the valid
5.2. Design of the chasers
Size of chasers
The chasers are manufactured in various sizes (width and length).
Two sizes of threads are installed in the cutting head ZR 26-I:
•
size of chaser S02 (14.5 x 6.5 X 32)
For cylindrical threads and short conical threads
•
size of chaser S09 ( 22 x 7 x 32 )
Mainly for conical threads
Please refer to the holder table in the annex for the required size of the chasers.
Chaser profile
The chaser profile consists as mentioned before of parallel grooves which correspond
to the profile of the thread to be cut.
Example:
Metric profile with lead angle of 60° according to DIN 13, or Whitworth profile ac-
cording to ISO 228 resp. to B.S. 84 with lead angle of 55°.
Chaser first cut
The chasers are manufactured with various first cuts in order to meet the different
operating conditions. This first cut is not being altered and lasts for the whole service
performance of the chaser.
First cut extra short:
For workpieces without oversize with a thread against the collar and very short thread
run out
Thread run out approximately 1, 5 x lead
Only suitable for free- cutting workpieces
The actual chipping tool is the chasers.
They are fitted with a plain thread profile
which means threads with various diameters
and the same lead can be cut with just one set
of holders.
For instance M6, M8x1 and M12 x1 in which
according to the different lead angles and
diameters various types of holders have to be
installed.
Thread- and holder tables:
see page 19 to 20
thread run out.
Operating Manual ZR 26-I
Chasers
9
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