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powerhound (Mechanical) (OP)
9 May 13 15:17
I need a little help here.

How would I go about ensuring that the flat on the internal D-hole is oriented to the gear tooth pattern? We are referencing an AGMA spec to dictate the geometry. I don't know the number of the spec. My assumption is that the tooth geometry--and tolerancing--is dictated by the spec and the spec probably doesn't use profile to tolerance the tooth geometry. If we were to define a tooth with basic dimensions then we could get simultaneous requirements to apply but we'd rather have the spec define it. Any ideas?

Before you guys slap me around too badly, I have no real experience with gears so have a little mercy on me.

Thanks,



John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

CheckerHater (Mechanical)
14 May 13 8:43
As a last resort you can always use verbal note.

This is what I was able to find in Genium Manual:

fsincox (Aerospace)
14 May 13 13:00
Chances are pretty good in my book that neither tooth is really a primary datum, that’s what I thought this modern stuff was supposed to be for?
Frank
powerhound (Mechanical) (OP)
14 May 13 16:20
I'm not showing a tooth as a datum, Frank. I'm trying to orient the flat in the D hole to the gear tooth pattern. Believe me, I'd love to just define the teeth with basic dimensions, use a profile control, and let simultaneous requirements do the rest but we aren't there yet.

John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

CheckerHater (Mechanical)
15 May 13 8:08
Tooth can be used as a datum, and simultaneous requirement is not the only way to control things.
fsincox (Aerospace)
15 May 13 8:42
sorry powerhound, I was refering to the Genium picture.
CH,
I agree a tooth can be used as a datum, I do not think it is generally, functionally speaking, a primary datum.
Frank
CheckerHater (Mechanical)
15 May 13 9:46
Frank,

Please see my sketch as "intentionally incomplete"
I am not setting primary datum, just giving example what the datum may be.
fsincox (Aerospace)
15 May 13 10:04
Thanks, CH,
I would tend to do just what powerhound has done, in the OP, and added CH's dim accross a tooth and use a position of the tooth at pitch line. Face(I assume) is primary, bore is secondary and flat is tertiary. I see this as a functional definition (assuming I have correctly read how it functions). Bore could be primary if face is not fumctional :)
Frank
powerhound (Mechanical) (OP)
15 May 13 11:12
CH,
I know that simultaneous requirements is not the only way to control things, it is just one easy way that I can think of. Your example is another way.

John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

Helpful Member!  CheckerHater (Mechanical)
15 May 13 11:41
I didn't mean to offend.
It is really nice to dimension everything from the same datum framework, and, as a bonus, get everything glued together by simultaneous requirement without extra effort.
But sometimes you have to make a choice to control one feature WRT other.
There was a thread on this forum about practical ways to clock gears:
http://www.eng-tips.com/viewthread.cfm?qid=111643
The posters generally agreed that it is better to cut teeth first.
So, using tooth as a datum was not exactly part of my evil plan. smile
pmarc (Mechanical)
16 May 13 15:07
Why not to specify a "width" dimension across the tooth without any value (if the tooth geometry is controlled by other specs) at a certain basic diameter (e.g. pitch diameter or any other diameter) and apply positional feature control frame at RFS wrt A|B|C preceded by "15X" prefix. Wouldn't this control orientation relationship? By rhe way, this would not fall under simultaneous requirement concept, because the flat and the teeth would not be controlled to the very same datum reference frame A|B.
fsincox (Aerospace)
16 May 13 19:05
pmarc,
I agree with pmarc, that was also my point about the proposed Genium solution, it is not really up yo date.
CheckerHater (Mechanical)
17 May 13 8:37
The good thing about Genium approach is that it is correct functionally.
When you make tooth a datum, you imply that said tooth is somehow more important than others.
pmarc (Mechanical)
17 May 13 8:45
CH -- I am having troubles to see where exactly Genium example says that a tooth is used as datum feature. Could you clarify?
CheckerHater (Mechanical)
17 May 13 9:21
I say Genium DOESN’T SAY tooth is datum feature and it’s the good thing.
fsincox (Aerospace)
17 May 13 14:02
I am saying the Genium approach is the "old way" and overly simplistic for tolerancing. A tooth, if referenced, is generally goint to be for clocking and not as a primary datum, functionally.

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