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Geometric Tolerance question

Phenom
Phenom

Probably not the right place to ask this, but there are so many brilliant people on here -

I have a stepped cylindrical part and want to apply a perpendicular tolerance relative to a plate that it is welded to.

If I attach the geometric tolerance symbol to just one section of the cylinder, does that imply the remaining sections are included ?

Or should I attach it to the axis centreline of the cylindrical part - which makes more sense to me but I'm not sure it is correct.

Every example I can find shows only a plain cylinder, with the symbol attached to the cylindrical surface.

HP Z420 16GB RAM
Quadro K4000
SE2019 MP5 on Windows 10 Pro 64.
12 REPLIES 12

Re: Geometric Tolerance question

Gears Esteemed Contributor Gears Esteemed Contributor
Gears Esteemed Contributor

I would expect it to need to be attached to each feature , so if stepped, each cylcindrical step would need it's on FCF.



Ken
Production: SE 2019 MP5, Testing: SE 2020
http://Grundey.blogspot.com

Betreff: Geometric Tolerance question

Gears Esteemed Contributor Gears Esteemed Contributor
Gears Esteemed Contributor

Hi @beachcomber

 

 

without having a draft or picture it isn't that easy to give the right answer, but IMHO and depending on the length of those cylindars, I would like to say that either You take the longest cylinder as datum or You put all (or some) of them into a common datum base A-B

 

The only wrong method AFAIK is to use the center axis itself.

This is something what isn't defined any more (this was possible before 1998 or 2002)

 

 

 

 

regards
Wolfgang
Highlighted

Re: Geometric Tolerance question

Gears Esteemed Contributor Gears Esteemed Contributor
Gears Esteemed Contributor

I tend to agree with @KennyG. Since a centerline is virtual it's not really appropriate since you're trying to control the cylindrical faces. I suppose it might be legal to apply it to one face and attach a note saying it applies to all cylindrical features.

Just my .02

Bruce Shand
SE2019 MP5 - Insight - Win10 - K4200

Betreff: Geometric Tolerance question

Gears Esteemed Contributor Gears Esteemed Contributor
Gears Esteemed Contributor

HI @beachcomber

 

 

sorry, it seems as I have confused the situation.

 

You want to have the plate plane as datum and the cylindars as target?

 

Then You have either to put a geometrical tolerance to each of those cylindars, or - what I suppose as to be better - give them a common zone, that all of them have to be in one and the same tolerance area.

 

regards
Wolfgang

Betreff: Geometric Tolerance question

Phenom
Phenom

Thanks for all your input - you have pretty much confirmed what I thought. I was sure that in the past you could apply the tolerance to the axis - as @hawcad indicated.

The image below shows the assembly in question.

The problem for me is that the important bit is the end indicated - this is where a mating part locates.

It is only a short length of the part (dimensions only shown for your reference) and I have been given the tolerance value of 0.4mm. The 19 & 56 long sections do not really matter.

I think the 0.4 is a bit loose for the short length, but as time is tight on this job its going to be a case of JFDI here.

2016423.jpg

 

HP Z420 16GB RAM
Quadro K4000
SE2019 MP5 on Windows 10 Pro 64.

Betreff: Geometric Tolerance question

Gears Esteemed Contributor Gears Esteemed Contributor
Gears Esteemed Contributor

Not sure if it applies here for you but a projected tolerance zone can help to keep a short feature's effective nominal tolerance tighter.

Bruce Shand
SE2019 MP5 - Insight - Win10 - K4200

Betreff: Geometric Tolerance question

Phenom
Phenom

@bshand - just looking on the 'net and I don't think the projected tolerance zone can be appled here.

It seems to be applicable to holes into which a stud is inserted. We don't use GT all that often, other than positioning of multiple holes, so I'm a bit behind the times on the subject and hadn't even heard of this.

It could, I think, be applied to the hole in the plate to maintain that perpendicular to the datum face.

HP Z420 16GB RAM
Quadro K4000
SE2019 MP5 on Windows 10 Pro 64.

Betreff: Geometric Tolerance question

Gears Esteemed Contributor Gears Esteemed Contributor
Gears Esteemed Contributor

It can be applied to male features as well. Example, a dowel pin. Or even a stud.

It's a theoretical zone so agnostic regarding feature type.

(I think. I was wrong once.)

You have a possible point about using it for holes only. Though I can't find any prohibitions about using it for male features I can't find any examples of that use online.

Bruce Shand
SE2019 MP5 - Insight - Win10 - K4200

Betreff: Geometric Tolerance question

Gears Esteemed Contributor Gears Esteemed Contributor
Gears Esteemed Contributor

Hi @beachcomber

 

 

 

is it possible to indicate the mating cylinder faces on that image?

 

Will the mating part fit on the back only, the front only or on both cylindars ?

 

If both then You should use a common tolerance zone for that indicating the two partly cylindars to clarify it clearly for every manufacturer.

regards
Wolfgang