Aligning two axis

[heypoopy]

I am trying to figure out what I have to use to make two cams, one on each end of a roller, to be aligned with one another. The cams have an alignment hole in the same spot. I'm confused with the datums and if I even need them.

 

[KENAT]

Do you work to ASME Y14.5, and if so what release.

Fundamentally just showing to items aligned does not imply any relationship - you have to somehow tolerance this.

The best way to do this varies with situation.

For instance if the roller is long and the cam function related to its OD then it may make sense to make its OD the datum feature.

You could then relate both 'cams' to the roller OD.

Alternatively it may make sense to relate whatever mounts to the cam alignment holes.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[CheckerHater]

It's hard to suggest anything without picture.

If you want to design a shaft the cams will be attached to, look into ASME Y14.5-2009 Fig.4-40 and Fig. 4-41.

 

[Belanger]

If you were talking about two circular pieces on each end of a shaft, the easy answer would be a position tolerance ... and this would be the one rare case where no datum references are required (they each kinda become a datum for the other).

But because you are talking about lobed cams, the best GD&T option is profile. This would control the shape, size, orientation, and location (axial only) of the two cams. Just as profile can be used to align two coplanar flat surfaces, I'm thinking that a similar scheme can be constructed here. Just do an all-around profile tolerance (no datum references) on the cams and be sure to say 2 places or something.

However, I'm interested in others' comments on my suggestion.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[pmarc]

Like Checker, I'd like to see at least a rough sketch of the case.

 

[pmarc]

J-P, I believe approach shown in fig. 4-34 in Y14.5-2009 is something what you are suggesting (just without datum feature symbol attached to profile FCF), right?

 

[MechNorth]

J-P, yup.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com