Shaft and Hole designations used in American-British-Canadian System (ABC) 2

[DrBwts]

Hi,

I was wondering if somebody could explain the meanings of the symbols used in the shaft and hole designations of American-British-Canadian System (ABC)?

So far all I have turned up are cut & paste paragraphs from Machinery's Handbook which mentions the symbols eg H7, p6 etc but nowhere can I find a description of what 'H' or 'p' etc actually mean.

Thanks

Nic

 

[KENAT]

DrBwts, they are classes of fit, maybe this link will give you a starter for 10.

http://www.cobanengineering.com/Tolerances/ANSIForceFits.asp

Posting guidelines faq731-376

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

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

 

[drawoh]

DrBwts,

Do you have a whole Machinery's Handbook? It is the bible around here. I am less interested in the tolerance classes, and very much more interested in the fit classes, explained in some detail. The tolerance classes are used to achieve these.

I keep a handout in my Machinery's Handbook that I was probably given in college, that explains the fits in somewhat more detail. I do not know where it came from.

The tolerance classes actually are an ISO standard, also explained in the Machinery's Handbook.

--
JHG

 

[DrBwts]

Thanks KENAT I'm looking for something that explains what the actual designations 'H' or 'p' or 'g' mean.

I get that H7/h6 is a nice snug clearance fit or that H11/c11 is a loose running fit but what does having a 'H' or a 'c' mean?

 

[DrBwts]

Hey drawoh

Yes I have copy, I was looking up some stardard tolerances when the thought occured 'is there some logic to the letters & numbers used?'

 

[Occupant]

Capitals "H" are used for holes. lower case "h" are used for shafts - in other words male parts. There is the concept of "unit shaft" - not frequently used - were you pair the h-tolerance field with every thing else and also "unit bore" were the "H" gets paired. The "H" and/or "h" is something like State street in Chicago, the dividing line - to the right you have letters "i" through "z" were every thing gets tighter as you go and to the left you have letters "g" through "a" were it is the other way around - it gets looser.

 

[KENAT]

The letters themselves designate tolerance classes DrBwts. As Occupant says lower case/upper class designates if it is a shaft or hole.

Posting guidelines faq731-376

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

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

 

[DrBwts]

Thanks Occupant, what about the numbers eg H7/h6?

 

[Occupant]

H(bore)/h(shaft) is known as a locational fit - where parts are closely mated without interference so that they can be easily assembled and disassembled. The numbers indicate the tolerance field, the larger numbers a generally chosen for the bores because those tolerances are more difficult to achieve in machining. E.g. H7 (and also h6) can generally be obtained by grinding, hard turning, broaching etc.

 

[c0rd0bes]

you can thank our european cousins for this , years ago I remember you had press fits, interference, running and sliding fits.. things used to be easier

 

[juergenwt]

You need to get DIN/ISO 286 part 1 and part 2.
ISBN 3-410-12677-5
A small pocketbook from:
All Dim's are metric.
Learn how the system works.
Just getting the numbers for a certain combination will help you one time only.
But you really need to understand the system.
Good explanation here:

http://www.gbi.bgk.uni-obuda.hu/oktatas/segedanyagok/muk/Engineering_Communication/2012/ea_03.pdf

Here is a start:

http://mdmetric.com/Ch6.8wGO.pdf

You can call or fax Beuth and ask for the pocket book in English on DIN/ISO 286
ISBN 3-410-12677-5
Approx. $20.00

Call or fax: Phone: +49 30 2601 2759
Fax: +49 30 2601 1263

From the US use 011 to get out, than 49 to get into Germany

 

[DrBwts]

Thanks juergenwt that was exactly what I was looking for.