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carcru
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Multiple Tolerance Ranges for Parts?

09/14/2009 2:07 PM

Is it possible or customary to specify various tolerances ranges for a single part? For example, if the overall tolerance for the entire part is +/-0.01", but there is a hole which cannot deviate beyond +/-0.005", is this achievable?
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RVZ717
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#1

Re: Various tolerance specs for a single part?

09/14/2009 2:22 PM

Absolutely.. Multiple Tolerances can be on a single part, It all about how its put on the drawing... You can have a general Tolerance for the whole part which all tolerances (any that are not called out) must fall within, however you can have any other tolerances on the part you wish, as long as each "special" tolerance is called out. All Tolerances not called out specifically must fall within the "Default" Tolerance.

Somewhere on the drawing, you should find a note which dictates this to some extent.

For more information you might try looking up some GD&T (Geometric Dimensioning and tolerancing) information on google. ASME have made a book of standards regarding all of this information. I currently have the Y14.5-2009 standard.. But I think they just released the new version.

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lyn
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#2
In reply to #1

Re: Various tolerance specs for a single part?

09/14/2009 2:29 PM

Yep! Agreed.
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Q
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#6
In reply to #1

Re: Various tolerance specs for a single part?

09/15/2009 11:11 AM

ASME Y14.5-2009 is the latest.

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markar
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#3

Re: Multiple Tolerance Ranges?

09/14/2009 3:48 PM

When you see UOS (unless otherwise specified) it's "go hunting time".

Read a print like a contract - because it is. Research any call out that you don't understand and if your stumped then have the customer explain it using an example.

It's cheaper to eat pride now than bad parts later.

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Haajee
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#4

Re: Multiple Tolerance Ranges for Parts?

09/15/2009 3:14 AM

Regards.

In << overall tolerance for the entire part is +/-0.01" >>

<< a hole which cannot deviate beyond +/-0.005 >> has 2 tol be specied:

1. The position of the HOLE &

2. the size.

1st cannot be & the 2nd should be
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Dutchy
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#5

Re: Multiple Tolerance Ranges for Parts?

09/15/2009 3:39 AM

Is this the position of the hole or the diameter (assumed). If it is the diameter then you can achieve this with the right machining methods but if it is a positional tolerance then it depends on where the dimension reference is. If the tolerance on the dimension reference affects the positional tolerance of the hole then you have a problem: choose a different reference.

Dutchy

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Anonymous Poster
#7

Re: Multiple Tolerance Ranges for Parts?

10/29/2009 10:23 AM

is it the hole size or the feature size, both are acheavable, what is the difficult in this????
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CATIA_GURU
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#8

Re: Multiple Tolerance Ranges for Parts?

06/11/2010 3:43 PM

The replies have been correct.

Consider that the overall length of a part may deviate significantly, but that the distance between the datum feature and the hole is much more critical.

A good example would be a situation where you have a machined bolt pattern on a wing skin for an aircraft. Per thermal expansion, a 500 inch long wing skin will expand .00655 inches per degree fahrenheit. So if you start with a 500 in long wing skin at 70 deg in the morning, when the shop reaches 80 deg in the afternoon, the skin is 500.0655 inches long.

But at a specific location on the wing, a bolt hole pattern has a +/- tolerance of .001 between holes. Why is this possible? Because the expansion between the holes is very small comparatively.

Another example is that the overall part dimensions aren't critical because the part has room to fit against other parts though a specific feature in the middle of the part must be aligned so adjacent parts will fit in that area as well.

I hope this helps!
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Anonymous Poster (1); CATIA_GURU (1); Dutchy (1); Haajee (1); lyn (1); markar (1); Q (1); RVZ717 (1)

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