Gear Cutting Tools

The effect of cutter deviations and cutter clamping
errors on the gear (for single-start hobs with 20° pressure angle and relief rake angle of approx. 10°)
The quality of a hobbed gear is the
product of the interaction of various
components and production
conditions.
The deviations from the intended
geometry of the hob and the
clamping errors of the cutter on
the hobbing machine play an important
part in this.
In hobbing, a distinction is made
between the deviations on the enveloping
helix of the cutter and the
deviations on the cutting faces of
the cutter.
The deviations of single-start hobs
affect the quality of the gear mainly
in the form of profile deviations.
It is here important to know in
which order of magnitude the deviations
on the hob and clamping errors
of the cutter affect gear quality.
Hobs
Nature of the
deviation
Designation and symbols of the
deviation acc. to VDI 2606
Item no. & symbol of the
deviation acc. to DIN 3968 (-
Sept. 1960)
Representation of the deviation
Deviations on the
enveloping helix
of the hob
Total base pitch deviation F pe within an
engagement area
No. 17
F e
Path of contact
Tip
Root
Cutter lead height deviation in the
direction of start F HF between any
cutting edges in one convolution
No. 15
F HF
Profile formation zone
p z
Radial runout f ra on the tooth tip
No. 6
f rk
1 cutter turn
Tooth thickness deviation f s on the
basic reference cylinder
No. 13
f s
f s
No. 12
Form deviation F fS of the cutting edge
F fS
Active profile height
Tip
Root
Deviations
on the cutting
faces of the hob
Form- and position-deviation F fN
of the cutting faces
No. 7
F fN
active profile height
Tip
Root
Cumulative pitch deviation F pN
of the gashes (cutting faces)
No. 10
F tN
1Hob revolution
Gash lead deviation f HN over 100 mm
cutter length
No. 11
f HN
Profile zone generating
100
Clamping errors
of the hob on the
hobbing machine
Radial runout f rP on the two indicator
hubs
No. 4
f rP
1 Hob revolution
Axial runout f rx on the clamping faces
No. 5
f ps
1 Hob revolution
132