Page 155 - JBO-Katalog-2022

Technical Information M
MF
MJ
EG M

G
Rc, R
Pg

UNC
UNF
UN
Die nomenclature Cutting dies tolerance classes Preparation of workpiece UNJF
If no tolerances are specified The workpiece to be cut is
in the order, we supply dies for provided with a centric chamfer.
NPT
ISO metric threads to satisfy This makes it easy to cut and NPTF
chamfer class 6g tolerances (≤ M 1.4 produces centric threads. The
chip hole
tol. 6h), dies for Whitworth bolt diameter must be smaller
pipe thread to satisfy class A than the nominal diameter of
tolerances and for dies for Uni- the thread to be cut (see guide
fied National Thread to satisfy lines in tables on pages 158
class 2A tolerances. We also to 161). Cold welding in the
manufacture dies for ISO metric die thread outer diameter and
thread to satisfy 4h, 6h and 6e tearing of the threads can thus
tolerances, dies for be avoided. If the thread run-
spiral entry various undersizes (Whitworth out on the bolt is provided with
pipe thread) and dies for Unified a recess, this prevents the
D = outside diameter a = rake angle National Thread to satisfy class die from chipping on return.
(tolerance zone f8) b = chamfer angle 3A tolerances. These tolerance
E = thickness g = spiral angle
a = width of tooth zones, however, must be speci-
M
c = width of notch fied in the purchase order. Chamfer MF
b = diameter of hole for M keg.
fixing screw Standard chamfer: M taper
The following applies: The length of chamfer is
4h for ”fine” class tolerances indicated in the price tables. G
(bolt remains uncoated or is BSW
BSF
Specification thinly phosphated); DIN 477
70° (short chamfer): R, BA, Pg
Form A split Form B solid 6g for threads over 1.4 mm dia. Where threads have to be
6h for threads up to 1.4 mm dia. cut close to a shoulder, we UNC
UNF
supply dies with a reduced
UNEF
for ”medium” class toleran- chamfer length. The reduced UN, UNS
ces (bolt remains uncoated is chamfer length is approx. 1.25
phosphated or only provided pitches, which corresponds NPSM
NPT
with a thin electroplated to a counter sink angle of 70°. NPTF
protective layer) Tr, Rd
Customers cannot shorten the
chamfer by surface grinding,
6e for ”medium” class tolerances as this results in a chamfer
(thread is heavily electroplated). diameter that is too small, so
6e dies cut threads approx.
We supply our thread cutting dies in form B unless otherwise 0.03 mm smaller than 6g dies. that the die no longer cuts
specified on the order properly.
Other thread tolerances Shorter chamfer length on
on request.
request.

M
MF

G
BSW
BSF
R, Pg
MF-EL
UNC, UNF
UNEF
UN, UNS
UNJC
UNJF
Tel. +49 7432 9087 750 contact@johs-boss.de www.johs-boss.de 155 NPT
NPTF
Tr
EG