Max & Min Dimensions

[ModulusCT]

Simple question... When is the use of MAX or MIN appropriate?

When would a dimension like .060 MAX be preferable over .060 +.000 / -.010?

Am I telling the machinist by applying a MAX dimension that don't care if the dimension is .000? 9000 ft for MIN? My guess is yes... But then why would anyone want to use these terms?

 

[fcsuper]

There is no need to call out "full r max" as this is already covered by ASME Y14.5 and the tolerance of the slot itself. There is a section in ASME Y14.5 that covers 3 methods for detailing slots. The simplest method is to use the slot center for location, and then specify width x overall length, with a 2X R pointing to one of the radii.

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group

 

[vc66]

PeterStock-

Is that so the shop can just use whatever punch they have that fits?

i.e. for a .500 wide slot the call-out could be:

R.03+.22/-0

Allowing them to punch with whatever fits?

V

 

[KENAT]

fcsuper, I'd think PeterStocks approach is trying to give more freedom in manufacure of the slot, allowing square ends with smaller corner radii.

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[ModulusCT]

"There is no need to call out "full r max" as this is already covered by ASME Y14.5 and the tolerance of the slot itself. There is a section in ASME Y14.5 that covers 3 methods for detailing slots. The simplest method is to use the slot center for location, and then specify width x overall length, with a 2X R pointing to one of the radii."

Well, I'm thinking that calling out the max size is advisable when calling out the min, as he's done, while still not wanting to have a situation where the slot radii are produced beyond 'full R' (in other words, a hole at either end that exceeds the width of the slot).

But maybe I'm over thinking things.

 

[KENAT]

ModulusCT, the width dimension of the slot and the tolerance on it limits that. Within that tolerance I suppose the slot could be slightly 'bone' shaped.

That said, looking at Peters example again I'd have to question whether the 'MAX'on the end is really needed, though I suppose it balances the 'MIN' on the 2X .03.

It's one of those where I get the intent but wonder if it's more confusing than it's worth and if showing an 'Alternate Profile' may be better.

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[ModulusCT]

Unless I'm mistaken, the bone shaped issue could be remedied more clearly by calling out a controlled radius (CR) which limits reversals and other types of geometric deviations.

Eh?

 

[PeterStock]

I believe the intent on the slot example to allow manufacturing more options in making the slot. If they have a punch that make the slot with a square shape (with rounded corners) that would be acceptable. I do agree with Kenat that an "ALTERNATE PROFILE" view would make the intent clearer. I might do that instead of the note reference if I had any doubt about it being understood.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services

http://www.infotechpr.net

 

[KENAT]

Modulus, you really are over thinking it. The dimensions (length & width) and their tolerances adequately control function for typical slot applications.

In the unlikely event you are concerned about it being bone shaped by a few thousandths then applying additional controls is appropriate.

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[ModulusCT]

Fair enough...

I use the examples in Y14.5 to define slots, I'm simply saying that if someone wanted to control the dogbone issue, a controlled radius would probably be a more simple way of doing it as opposed to a MIN/MAX callout.

 

[KENAT]

ModulusCT, the min max thing wasn't intended to cover the 'dog bone' issue. It was to address the 'alternate profile' issue' off essentially using a rectangular 'slot' with corner radii.

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[ModulusCT]

Right, and someone mentioned that specifying the MAX in that scenario was unnecessary.

Maybe I'm not familiar with the part where indicating only the MIN is OK because the MAX is already defined per the spec being that the feature is a slot.

 

[KENAT]

Normally, the full R is defined by the width of the slot, no MIN or MAX call out needed.

Peters Note is trying to give to options. An essentially rectangular cutout with Minimum corner radii of .030. Or a conventional slot with R defined by the width. Given that the max R is limited by the width of the slot, I was questioning whether it was really needed to say 'MAX' at the end.

Frankly, this confusion is enough to convince me that using the note Pete put may not be a good idea.

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[aardvarkdw]

I have very rarely used "MIN" or "MAX" on a detail print because of the confusion it can cause and more than likely I am better off specifying a tolerance anyway to ensure that the parts are made to the design intent.

I do however use "MIN" and "MAX" on assembly and interface drawings. It is often beneficial to specify a min or max distance in relation to other components when you do not require a specific tolerance or when a tolerance is defined by the features of the detail parts and it is impossible to put the parts together in a fashion that requires a specific tolerance.

An example would be two plates held together with fasteners. The plates cannot be any closer together than .000" but it may be acceptable to have a .010" gap between them. In this case a tolerance of +.010 MAX would serve just fine.

David