Page 114 - Pafana

I. TOOLHOLDERS - technical information

toolholders for threading
Threading methods.
I.
Depending on the feed direction the following threading methods are listed:

a). towards the spindle b). towards the tailstocks

Machining allowance division. The thread root allowance can be divided as follows:
a). Radial approaching feed (conventional machine tools). a).

Where a “V” - shaped chip arises that is hard to control.
That method is applied in machining
hard materials (e.g. some grades of stainless steel).

b). Modified approaching feed along the side contour (CNC machine tools): b).
recommended.
It makes cutting conditions comparable with external turning (non - thread).
Good chip removal
conditions (chip curling or breaking depending on shape of insert’s top
(chip breaker) are provided.
High quality of thread surface is also guaranteed.

c).
c). Alternative approaching feed (CNC machine tools, lot production).

Lifes of both cutting edges are of comparable character.

General notes on determining values of approaching feed: - an approaching feed
value should amount at least
0,05 mm,
- it is recommended to decrease an approaching feed value in successive passes,
- in case of often damages of a cutting edge it is recommended to reduce an approaching feed (to increase
number of passes),
- in case an abrasive wear of cutting edge surface is observed a decrease of number of passes (increase of feed)
is recommended.

Usual number of passes depende on pitch thread.

P
[mm] 0,5 0,75 1,0 1,25 1,5 1,75 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0

Turn 48 32 24 20 16 14 12 10 8 7 6 5,5 5 4,5 4

Number of passes 4-6 4-7 4-8 5-9 6-10 7-12 7-12 8-14 10-16 11-18 11-18 11-19 12-20 12-20 12-20

® info.tech.
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