tolerances 1

[imaz]

Hi everyone. I need help on tolerances. We have many disagreements between manufacturing and engineering on tolerances. Beside how large or small the tolerances should be, we don't agree oh how they are specified and mostly stacking ones. What is a stacking tolerance? Is there a very easy book or a web side we can dowload pictures that explain simple and stacking tolernaces.By the way we are a fabrication, welding and asswmbly plnat.

On another note,I love this site. Thank you guys.

MT

 

[mrainey]

The simplest example of a stacking tolerance I can think of is - say you had four holes in a straight line.

hole 2 is dimensioned (located) from hole 1 (1.000 +-.005)

hole 3 is dimensioned from hole 2 (1.000 +- .005)

hole 4 is dimensioned from hole 3 (1.000 +- .005)

How far is hole 4 from hole 1?

It could be anywhere from 2.985 to 3.015 - a tolerance of +- .015

This probably isn't what the engineer intended, and might not work.

An alternative method for this example would be to dimension all holes from hole 1

 

[imaz]

Thank you.
What about the CL of the holes.(alignement)? Assume each hole is on different part.Location of this part is also a concern as far as tolerance.
If the tolerance on each hole diameter is +/- 0.010, what will be the tolerance of the pin that need to fit through all this holes?
I have tried the net, but can't locate free downloads for tolerances, any help?


MT

 

[peter26]

IMAZ

Try

http://www.boltscience.com.

They have softwares on bolt sizing and also accept inquiries.

peter26

 

[Drazen]

You obviously face many issues regarding tolerances, locational and dimensional. Maybe it is better to pass through one complete text on basics, rather then jumping from one solution into another problem. What you mentioned in second reply can be solved by defining locational tolerance as "free" or "related" or using "maximum material condition"depending on what you really need. You can find basics in, for example, "Machinery's handbook". Or, it is termed in American literature as Geometric Dimensioning and Tolerancing. (Try it on Google!)

 

[flexibility]

Hi imaz (Mechanical)

When talking about tolerances one actually means "allowence" which means the space between ajoining parts. The allowence may be divided between the two parts (i.e. shaft and hole) usually according to the processing capability.
Stacking tolerances has to do with the method of dimensioning. stacking is a problem if a dimension is computed one or a direct one. Dimensions given from a DATUM donot have a stacking problem.

You may find and book with easy explanation in:
Principles of Process Planning - A logical approach in section 4.3.1. Published byChapman & Hall
Or in Tool and Manufacturing Engineering Handbook - section on Tolerance charting