Face Milled vs. Face Hobbed

[Bruce2]

I recently learned there are two methods of manufacturing a Ring & Pinion gear set.
Face Milled:
Use a small screwdriver and put your thumb against it to measure the depth of the gear teeth at each end. A Face Milled gear has a tooth depth that changes significantly.

Face Hobbed:
The same measuring will show the gear teeth to be a constant height from one end to the other.

I only checked a couple. A Type 1 G type 3.88 (G831) is Face Milled. A Type 1 O type 4.12 (O412) is Face Hobbed.

According to the experts, when setting the contact pattern, each type of R&P reacts differently when changing shims.

Does anyone have a Klink type R&P to test?

[Pablo2]

There's a great illustration in some book I have .. but unfortunately, I'm a long ways and a couple weeks away from all my books and notes.

[dangerous]

The Klingelnberg and Oerlikon machines both produce a "face hobbed" set.
They also have a thicker heel on the teeth and usually a better radii in the root.

The Gleason machines are much faster to manufacture a gear set,
than the others (hence why most big manufacturers use them,
but usually appear as you describe.

Most higher loaded VW applications used or at least preferred,
the choice of Klingelnberg or Oerlikon for the above reasons.

It was just a manufacturing result that gave the G831 a bigger pinion head.

Yes I have found that the shimming is different for each kind.

[fastback]

good info
since i was unfamiliar with the terms i tried youtube



http://youtu.be/7paLPW3CjEs



http://youtu.be/tNks3OdE-FE

[Bruce2]

Thanks for the info on the K type gears, Dave.

Here are how the contact patterns move relative to shim changes:

FACE MILLED (Gleason profile):


FACE HOBBED (Oerlikon and Klingelnberg) :

[Bruce2]

It was just a manufacturing result that gave the G831 a bigger pinion head.

The size of the pinion head is due to the ratio. I haven't compared side-by-side a G type and a K type 3.88 to see if the head is about the same size. I suspect it is.

If so, why does everyone say the G type is strongest?

Wouldn't the K or O be stronger?

Why is the G type 4.12 the weakest of the three then?

The only info I've heard about the strengths is a comment that Eric Ballard said to me once, "the O type 4.12 is almost as strong as a G type 3.88".

[dangerous]

The pinion head diameter on the 8.31Gleason is much larger than the 8.31 Klingelnberg.

The 'module' of the 8.31Gleason tooth size making the head larger,
was what I was referring to, in your quote by me.

I am no expert,
but I think the claim of K being stronger, evolved from the fact that some teeth are thicker,
in the area that the pattern moves to under load.
K and O teeth are more tolerant than G under abuse,
but in an equal world,(if you could keep the crown wheel in mesh!)
the stronger tooth would have the biggest module.

This does not take into account that perhaps there are different material and heat treat results.

I have found the G833 to be quite strong and never broke one, only cracked with inadequate side cover strength.
In fact, keeping the crown wheel in mesh with good cases and side covers
can make most gear forms last brilliantly in most applications

I have noted that the G series seem to wear more,
or said differently, are more difficult to get a pattern on when worn!
but that is likely more due to the higher mileage and frequency that VW used them,
so may just be a higher mileage wear as opposed to wear due to tooth shape.

Interesting topic.

I like the details you posted relating to pattern movement,
but it should specify where the pinion shim is positioned if the recommendation is universal.
Some manufacturers shim the pinion, and some the bearing.

[Bruce2]

I like the details you posted relating to pattern movement,
but it should specify where the pinion shim is positioned if the recommendation is universal.
Some manufacturers shim the pinion, and some the bearing.

Here are some better pics. I changed the text to reflect the VW shim location.

G type:
http://images.thesamba.com/vw/gallery/pix/1264555.jpg

K and O type:
http://images.thesamba.com/vw/gallery/pix/1264567.jpg