Dimension of 1.5 +.3/+.1 Tolerances Interpretation

qcman

Registered Visitor
#1
Just to clarify something for me since even my customer is not sure. I have a dimension of 1.5 +.3/+.1 which I read as 1.6 minimum and 1.8 maximum. Is this a correct interpretation on my part?
 
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B

Brad Eickhoff

#2
Hi qcman,

We had a similar callout on an older print a few years back (minus-minus in our case) for NIST. When we called them regarding this dimension, their response was the same as your interpretation.

Hopes this helps, Brad
 

BradM

Staff member
Admin
#3
Just to clarify something for me since even my customer is not sure. I have a dimension of 1.5 +.3/+.1 which I read as 1.6 minimum and 1.8 maximum. Is this a correct interpretation on my part?
Hi qcman,

We had a similar callout on an older print a few years back (minus-minus in our case) for NIST. When we called them regarding this dimension, their response was the same as your interpretation.

Hopes this helps, Brad
Brad, are you sure?? I don't know, is the reason I ask. Most every tolerance I have ever seen is a value surrounding a nominal.

Basically as it is stated (which as you stated could very well be accurate), there is no minimum; but just a maximum. 1.5 means nothing. It is 1.6 to 1.8.

If as you say it's accurate, personally I see no value in it. I would think ANSI or a more appropriate reference should be established for writing tolerances, given the # of questions we have had here at the Cove on interpreting tolerances.
 

SteelMaiden

Super Moderator
Super Moderator
#4
This could be correct, but you know you can always check with the customer to make sure that all requirements are adequately defined. :2cents:
 

Tim Folkerts

Super Moderator
#5
If as you say it's accurate, personally I see no value in it. I would think ANSI or a more appropriate reference should be established for writing tolerances, given the # of questions we have had here at the Cove on interpreting tolerances.
I can think of at least one situation where such a tolerance might be used. Suppose you have a 1" pin to go into a 1" hole. The tolerances might well be 1.000 +0.002/+0.005 for the hole and 1.000 -0.002/-0.005 for the pin.



Tim
 
B

Brad Eickhoff

#6
Hi Brad,

I cannot say that the customer was correct but that was their response to us. At the time we had thought it was typo error on the print, and had made the part at what we thought was nominal. Their response was that the part was oversized due to the minus minus dimension. If I recall correctly he said that theses tolerance were not used too often in the USA, and it was a really old print. He did give me a reference to look it up at that time but we did not have the ref book to do this, so we just remade their parts to their interpretation.

So to answer your question Brad, no I am not sure, and in my 12 years of inspection I have only seen that call out twice with that same company. As mention the customer was the National Institute for Standards and Technology (NIST), yes I do believe that any company can be wrong, but they were adamant that the minus minus was not a typo. Although if anyone has a better understanding of these tolerance’s, I am all ears. Happy days to all.

Brad :D
 

BradM

Staff member
Admin
#7
I can think of at least one situation where such a tolerance might be used. Suppose you have a 1" pin to go into a 1" hole. The tolerances might well be 1.000 +0.002/+0.005 for the hole and 1.000 -0.002/-0.005 for the pin.



Tim
Let me get educated by Tim on this one. When you get a chance, can you explain this above? I don't understand it.
 
B

Britman - 2012

#8
I have in the pass seen these tolerances in this format, they're used to define fits between holes and shafts from a loose running to a force fit.

A good site for engineering issues is – "www.roymech.co.uk",

On the following page:

"www.roymech.co.uk/Useful_Tables/ISO_Tolerances/ISO_LIMITS.htm"

you will find an explanation on:

BS EN 20286-1:1993(ISO 286-1:1988 )...... ISO system of limits and fits. Bases of tolerances, deviations and fits

BS EN 20286-2: 1993(ISO 286-2:1988 ).... ISO system of limits and fits. Tables of standard tolerance grades and limit deviations for holes and shafts

This is one application for these tolerances – not sure if your customer?

Cheers
 
Last edited by a moderator:

qcman

Registered Visitor
#9
I have seen it on holes before but this is an open sided channel running the length of the part, auto related. Prints are coming from Japan and I have always interpreted it as I stated before. I have had some say it reads different so I thought I would put my mind at ease and ask you all. Must be a simple reason they do this, anyone know why?
 

Kales Veggie

People: The Vital Few
#10
Hi.

I have seen this before on drawings to define a clearance between a bore and a shaft. We produced a bearing bore diameter. The design engineering drawing specifies a bore diameter 17.000mm +0.005/+0.025. Our shop floor drawing would call out 17.015mm +/- 0.010. Our gages and master rings would be using the shop floor drawing and operators would target at the nominal dimension (=0.000 on a reference type gauge) and have a tolerance of 0.010 in each direction.
 
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