Adding tolerances to sketches

[Anonymous]

I have two interlocking machine parts and what to give the manufacture a tollerance between the parts.  I created two sketches, one for each part, however there are zero tolerance between the two, essentially sketched to a "perfect" fit.  Is there an easy way to add a 1/16in tollenace into the sketch?

I know I can go back and re input the dimension minus (1/16), but im looking to see if there was an automatic way to add an global 1/16 in tollerance between parts.

Thanks

Chris. 

[HughesTooling]

No there's no way to do that. Are you going to use the 3d model to machine the finished part or supply a 2d drawing with the limits and fits, actually even if you are working directly from the model you should supply a 2d drawing so there are no arguments later.

Can you attach a screen grab of what the joint between the parts look like, I might have a suggestion on an easy way to model it.

Mark

[TrippyLighting]

Are you talking about the sketch that uis used, for example to extrude 3D geometry from, or are you talking about the technical drawing used as the specification to manufacture parts ?

In Fusion 360 You can specify tolerances on the drawing, but not at the sketch level.

That could be useful, however,  for tolerance stackup analysis.

[josh.sapp]

I don't know if it will work for you but you can try this.

 I calculate everything in LMC, least material condition, and sketch everything in MMC, maximum material condition. Then when I make an assembly of the parts I can look at "Stack-Up"and interference.

There are standard "Fits and Tolerances" for mating parts. Most you tend to commit to memory after using so much. These can be found various places. In example: Machinist Handbook, Internet.

[Anonymous]

I don't see why you want to sketch with tolerance. I work with design and the tolerance is only useful in technical drawings.

It's better if you model your part with perfect fit because you can do future analysis. 

But if the two parts are modeled to not touch each other, than this is not tolerance, I would call clearance and I would insert it in the sketch.

[TrippyLighting]

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@Anonymous.BA wrote:

... and the tolerance is only useful in technical drawings.

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In other CAD software adding the tolerances can be done directly in the sketch and it can be very useful for tolerance stack-up analysis. You can even get third party software interfacing with these CAD softwares for that.

Also in other CAD packages there is the ability to directly use the dimensioning from the sketch in the technical drawing including the tolerances, with full assosiativity. In either place, in the sketch to the technical drawing can the dimensions and tolerances be changed and update in the other. I've used this many times and with a little forethought when sketching it's really quite a timesaver when creating the drawing.

[Anonymous]

Yes yes, I realize now that it can save a lot of time