Thread: What do these terms mean??

Thanks to Woodlee for supplying these to me some time ago Aluminium Alloy 6061 - Composition, Properties, Temper and Applications of 6061 Aluminium
Aluminum Specifications Cross Reference Chart

Tolerances Manufacturing and Engineering Tolerance Charts - Engineers Edge

Thanks wheelinround the first to are very useful but i still don't quite understand the tolerance thing.

Tolerance as in +/-0.10 is where an allowable amount of measurement differentiation can be tolerated.

Tolerance indicates how much variation there can be in a part.

+/- .01 indicates if a part is dimensioned as 30.00mm you could be 29.90mm or 30.10 mm and the part would still be acceptable.

The rule of thumb is if you are given full sizes the tollerance could be any where from 1 to 3 mm or 1/32" to 1/8" of an inch.

Really if you have no real understanding of what your asking or cant find it on google dont worry what ever your doing is not that important to warrant a tolerance.

The more decimal points following the dimension the tighter or more critical the tolerance.

Originally Posted by pipeclay

Tolerance indicates how much variation there can be in a part.

+/- .01 indicates if a part is dimensioned as 30.00mm you could be 29.90mm or 30.10 mm and the part would still be acceptable

You mean 29.99 or 30.01 don't you? +/- 0.1 would apply to the figures quoted. Maybe it was a typo and you got the decimal point in the wrong place?

Nev

Tolerance generally relates to parts that must work together, and require clearance for assembly or operation. The parts may be made by separate manufacturers, or on separate production lines in the same shop, including your own shop. There are various classes of fit, or looseness. Negative clearance is called "interference fit," and may be specified to limit distortions in the parts and/or to limit built-in stress in the final assembly.

Most often, tolerances in both parts allow imperfections in random parts, but still ensure quality of assembly or operation.

When precision is more critical, parts are sorted according to their deviations from ideal, and placed in separate containers. Ball bearings and their races are an example of this. Selective assembly mates oversize components with each other to achieve the specified clearance; ditto for undersize components.

Ray's (wheelinround) first link indicates permissible variations in chemical composition of alloys. This is a form of tolerance, too.

The objective of all this is to reduce waste, without requiring perfection. "The perfect is the enemy of the good."

Cheers,
Joe

So say the bit where the metal slides trough is 19mm wide and the bit that slides is 18.90mm does that mean the tolerance would need to be +/- 0.1 so it could move 0.1mm ether way.

If the hole was 19mm and the mateing part was 18.9mm the tollerance would be +.00/-.10mm,if it was +/-.10mm it would jam as your sizes could either be 18.90mm or 19.10mm.

Originally Posted by pipeclay

If the hole was 19mm and the mateing part was 18.9mm the tollerance would be +.00/-.10mm,if it was +/-.10mm it would jam as your sizes could either be 18.90mm or 19.10mm.

So this means that it can shrink 0.1mm and not expand at all.

If you want to put something inside something else with out an interference,the inside 1 should be smaller.

You could make them size for size and probably get away with it with out to much force required.

If the parts were to be adjustable or move inside one an other you would require more clearance depending on the application and what the material is you are working with.

What exactly are you trying to do or what do you want the end result to be able to do.

Originally Posted by Bupton

Hi there,
Just wondering what the tolerances or a general tolerance E.g. +/-0.10 was .

If it is a 'General Tolerance' then that tollerance applies to all dimensions on the drawing, unless specifically stated otherwisw.

A dimension on an engineering would look like;
19.00 mm +/-0.10 (ie 19.00 mm plus or minus 0.10 mm)

19.00 is the nominal size, and +/- 0.10 is the tolerance for that dimension.

This would mean that the dimension on the finished part could measure anywhere between 18.90 and 19.10 inclusive.

You would normally dimension a hole as 19.00 dia +0.10/-0.00 (plus 0.10, and minus nothing)
So that it could be larger but not smaller than nominal.

If you wanted a shaft to slide in that hole with a minimum of 0.05 clearance, you would normally dimension the shaft as 18.95 dia +0.00/-0.10. (plus nothing and minus 0.10)
So than it can be smaller, but not larger than nominal.

Unless you want a press fit, you never make the parts size to size.
ie 19.00 dia hole, and 19.00 dia shaft.

Hope that makes sense.

Originally Posted by Bupton

Hi there,
Just wondering what the tolerances or a general tolerance E.g. +/-0.10 was and what Aluminium – 6000 series, 7000 series means what i mean by that is what does the 6000 series and 7000 series mean.
Regards Ben

The tolerances have been covered for the most part.

The Aluminium series numbers (1000 thru 8000 and maybe 9000, I can't remember ) are basically the alloy recipes of the metals. Aluminium has a number of metals added to give the properties to the finished alloy and each series has a couple of main metals plus lesser amounts of others to give it the strength or working properties desired (weldable for example). Each series will have variations within the group. 7000 series for example are generally the strongest but can't be welded. Their main alloying ingredient is Zinc and 7055 can have as much as 8% in it. Makes it almost as strong as mild steal but corrodes if not protected. So the numbers like 7075, 7040, 7050, etc., all have differing amounts of Zinc in them along with the lesser elements to suit the end use. The "T" numbers after the main number designate the heat treat condition.

Pete