specification requier for hob cutter

[ushang70]

Hi, friends i m new here
my one customer reouiered gear with following soecification


NO. Of Teeth --------15
Diametral Pitch-------6/8
P.A.---------20
Pitch Dia---------2.5 Inch.


I Need Root Diameter And ASpecification Of Hob Cutter
I Am Also Looihnkg For Standard For ABove Specified Gear

UShang

 

[diamondjim]

The 6/8 indicates basically a 6 dp
gear that is stubbed 6/8 times the
basic addendum and dedendum
full depth ratios of a 6 dp gear.

The addundum would be .125 and
the dedendum would be .15625.
Tooth thickness pi/(2X6) = .261799
The pitch is simply pi divides by 6.

For a hob cutter the the addendum is equal
to the dedendum of the gears to fully
cut the addendum of the gear. I assume
it is a 20 degree pressure angle.
This type of standard was created by the
Fellows Gear Company many years ago
and designated Fellows Stub profile.

The first number designated the basic
diametral pitch and the second value
determined how to calculate the addendum
and dedendum.
The addendum is 1.000 divided by the second
number of the ratio ie 1.000/8 = .1250
and the dededum is 1.250 divided by the second
number of the ratio ie 1.2500/8 = .15625
Often people use the standard stub hob to cut
fellows but it does result in having a deeper
dedendum rather than having two separate hobs
in stock. This stub gear system allowed
smaller numbers of pinion teeth to be used that
were not undercut. Usually 14 teeth being
the minimum number of teeth allowed without
having undercut in the root whereas in the
full depth system it was 17 teeth. These teeth
are stronger but you do loose contact ratio
and tend to be noisier than full depth teeth.

 

[ushang70]

Thanx Diamond
its really nice to c your post. After very long time i got one logical solution.

Let me go through your calculation. N i'll come back to u.


Thanx A lot


Cheers

Ushang.