Feature quantity and centerline dimensioning

[astumpf]

Hey all,

I'm looking for a tip or a direction. The die cast parts I'm working on have some complex geometry and significant draft. We are using centerlines to help dimension features in relation to each other. I've rarely used centerline dimensioning (don't even think it's ASME Y14.5 approved). The benefit though to this is that we only have to dimension one of the features on the left or right side of the part due to symmetry. My question lies in this. We normally call out hole quantities in our drawings. Do I still need to do this when using center lines? I'm redlining a drawing now and removing quantity call outs for other features (angles, thicknesses, lengths, etc.) due to the centerline, but keeping quantity callouts for holes. Is this valid? Thanks for your help!

Aaron

 

[ctopher]

Qty for holes is helpful.
Try to think like a machinist, what info is needed to make the part?
All features need to be clear.
Also, make sure the CL is clear to indicate if it's the CL of a feature or CL of the part.
The CL symbol is not used anymore, although a lot of people still do.

Chris, CSWP
SolidWorks '16
ctophers home
SolidWorks Legion

 

[KENAT]

Give us a sketch to show what you mean by center line dimensioning - I've seen/heard the term used to mean different things.

Just showing features on a common centerline doesn't imply any alignment tolerance per ASME Y24.5M-1994 section 2.7.3.

However, if you are using Position or surface profile tolerances etc. with Feature Control frames giving the tolerance for each feature then that addresses this problem - so long as the centerlines either represents a datum or is dimensioned from one via basic dimensions. Note the centerline itself is not a datum, but it can represent a centerplane of a datum feature which can be a datum.

Likewise if you are dimensioning to features from centerline, the centerline itself needs locating. Using 'GD&T' as mentioned if the centerline represents a datum or is located from a datum by basic dims, and you have basic dims locating your features from the datum with FCF for the features, this can work.

If you mean you're using hole patterns with centerlines between holes rther than extending dimension leaders then no you don't need to add the number of instances to the locating dimension see ASME Y14.5M-1994 figure 5-4 for example.

However, you do need to put the number of holes on the size information of the hole.

Posting guidelines faq731-376

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

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

 

[drawoh]

astumpF,

If your fabricators and inspectors need to know the quantity, you should specify the quantity. Centrelines have nothing to do with this.

--
JHG

 

[astumpf]

Thanks all. Much appreciated. We will be ensure proper geometric referencing. Thanks for the help.