Staightness of a tapered pin.

[Madhu454]

Hi All,
have one more question on straightness.
How to control the straightness of a Tapered Shaft.

 

[dingy2]

pmarc:

I could set up straightness of the axis of a tapered feature very easily in a chuck or CMM.

Now, profile of a surface, we measure the surface for any variation from the true (theoretical) shape of the feature which would be shown in basic dimensions. It does include straightness but also roundness and size variation.

I would still use straightness.

Dave D.

http://www.qmsi.ca

 

[Belanger]

Oh boy, I see where this is going. Can you apply profile to a cone where the size of the cone is not a basic dim? That can of worms was another thread...

http://eng-tips.com/viewthread.cfm?qid=302470&page=2

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

 

[fsincox]

I think you are correct that is the way they want us to handle features that look like that, but, unfortunately this is all based on simply "it is a feature that looks like this" and not anywhere do they describe what its function is. That was supposed to be the important part of all this.
The OP is looking for straightness of the axis your answer seems to amount to "it can't be done". That is what some of us find so unsatisfying, beacause, it can be just not here.
IMHO, the simplicity of the ISO solution on is an elegant solution. If you want to check it as runout that is your business just let me specify what I wanted/needed. In the ISO standard they show it applied to the centerline of a something like a coke bottle. Does anyone here really not understand the intent when you see it?
Frank

 

[pmarc]

Dave,
I have no remarks to the set-up you proposed. What I just wanted to say is that since the method of defining straightness of median line for conical/tapered feature on a drawing is not clearly specified in Y14.5 you can have situation when one person may understand the method you proposed, while second one may not. Therefore you have to very clearly specify how to interpret 'your' straightness callout, otherwise at the end you will be probably forced to come back to the standard and face with the fact that this idea is just your private proposal of specifying one of geometrical characteristics.

J-P,
I was not thinking about combining profile of surface with directly toleranced dimensions. My point was that this situation is another one where 'classic' profile approach - with everthing basic - seems to have advantages over other tolerancing methods.

And Dave, I do not see a problem with including circularity (roundness) and size at the same time. If one wants to fully describe a conical feature, size, form orientation and/or position have to be somehow defined. Of course OP's question was about straightness only, but in reality straightness only is quite unlikely to happen, so other characterstics will have to be added anyway. Why not go with profile of surface which gives all that we need?

 

[pmarc]

Frank,

I agree that ISO method is an elegant one. But imagine what would happen if there where 3 or 4 or more coaxial features present. Would it be equally elegant?

I do not know exactly which drawing you are refering to (although I could promise I saw it somewhere), but if you take a look at Annex A of ISO 1101:2004 you will find out a clear statement that the method you are proposing is considered to be ambiguous and it should not be used any longer.

 

[Belanger]

pmarc -- I mentioned the toleranced diameter (with profile) because the idea is to control straightness (form) but not size.

I agree that profile will be an easier method, but having a basic diameter would go beyond what the OP asked.

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

 

[fsincox]

pmarc,
Thanks, I only have the earlier (1984) version.
Frank

 

[ptruitt]

Perhaps the question is the problem. Why try to control something that does not physically exist?

Peter Truitt
Minnesota