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Max & Min Dimensions

Max & Min Dimensions

Max & Min Dimensions

(OP)
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?

RE: Max & Min Dimensions

We use these terms a lot.  For Example of threads and a tap drill.  We specify A max depth for the tap drill and a min full thread depth for threads.  This way we can control the thread depth but leave it up to the machinist on how deep to run the tap drill with in our max limit.

RE: Max & Min Dimensions

ModulusCT,

   I have used the MAX dimension when I draw something that looks like an aluminium angle.  I specify a radius of 12mmMAX.  The minimum acceptable radius is zero, as you noted above.  This allows the fabricator to use stock aluminium angle, if he has any lying around.

               JHG

RE: Max & Min Dimensions

I also use the terms frequently, when specifying a fillet radius for example.  If stress is not an issue, I see no reason to tie the machinist to a tolerance unnecessarily.

"Good to know you got shoes to wear when you find the floor." - Robert Hunter
 

RE: Max & Min Dimensions

I do not like to use MAX and MIN dimensions. Used like Sdeters states for threaded holes is good, but otherwise I prefer to explicity give an acceptable range. If the dimension is .060 MAX, then 0 needs to be acceptable. If the dimension is .060 MIN then 99999.999 needs to be acceptable, if the part will allow it. The min dimension for the full thread in Sdeters example was limited by the depth of the tap drill. If that dimension was not given, then it must be acceptable to drill and tap thru the entire part.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
www.infotechpr.net

RE: Max & Min Dimensions

(OP)
OK -

So use carefully... And probably sparingly, in only a handful of situations. I like the thread depth use and the min radius sounds like a handy application for me.

Thanks.

RE: Max & Min Dimensions

Agreed, use sparingly.  I also agree with Peter's point that extremes must be acceptable to use the terms.  There are situations where extremes are allowable.

"Good to know you got shoes to wear when you find the floor." - Robert Hunter
 

RE: Max & Min Dimensions

If you measure from an edge to a center of a hole, then indicate "max", the machinist could give you half of a hole on the edge.

Chris
SolidWorks 09, CATIA V5
ctopher's home
SolidWorks Legion

RE: Max & Min Dimensions

And watch what you use for a nominal. If a vendor takes you model and runs with it that R.060 MAX fillet could easily come in .070 or so and cause an interference. Yes it is not to the print, but you would have needed to inspect that feature to find it.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
www.infotechpr.net

RE: Max & Min Dimensions

If in doubt regarding the use of the terms, you could always indicate allowables in your tolerance, i.e. "R.06 +.00/-.06" is essentially the same as "R.06 MAX"

"Good to know you got shoes to wear when you find the floor." - Robert Hunter
 

RE: Max & Min Dimensions

We used a min/max value on a radius for glass headlight molds around the lugs that orient the lamp into your car. We didn't have it at first, just had the finish shop do a blend with no spec called out. On one batch of molds the finish guys over worked the radius and the glass was failing inspection because the radius was too large and wouldn't let the lamp seat properly. Modified the drawing with a min/max radius and the problem was solved.

 

"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli

RE: Max & Min Dimensions

We also have use it in a tapered core in a die casting or any process that one needs to have draft.  You call out the top of the core a Max Diameter and at a gauge dimension depth, call out a min diameter.  So we let the manufacturing process Die casting help in determining the min max.  So one can have a straight walled die casting or a one with draft with in the limits of the max call out at the top of the core.   

RE: Max & Min Dimensions

looslib,

  You bring up a major point of contention I've had with a customer I used to have to deal with. With the original print there was no specification on the radius yet you were getting good parts, then one day you got parts that didn't work yet they were manufactured using the same print. Wasn't there a huge uproar that originally blamed the manufacturer for the error since the print had "worked" in the past? The customer I dealt with had used certain vendors for years and when they went through a big cost savings crusade, they had things re-quoted and began to use different vendors. The result was a lot of bad parts made to print. The prints were not very good and the previous vendors had worked their way through the issues over the years and had figured out what the customer had wanted. The first knee jerk reaction was that the new vendors were morons because the prints were yielding good parts before the switch and it took an act of Congress to get them to see that the prints were the problem, not the vendors. The biggest issue was the misuse or non-use of GD&T.

Anyway, I don't mean to hijack the thread, I just wanted to know if the manufacturer originally got the blame for the non-functional parts.

Powerhound, GDTP T-0419
Production Manager
Inventor 2010
Mastercam X3
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

RE: Max & Min Dimensions

I use a lot of max radii on turned part inside corners.  The tool can never produce a sharp corner but even if it could, zero would be OK (no stress issues).  Too much radius from a broken down tool can be a problem.  Just using a max dimension makes it easier to inspect.  Typically I will model at half the max value.

I use a lot of max values for draft angles too.  I don't care if the mold maker uses zero draft if they can get the part out of the mold.  Usually, the mold maker will use very nearly all the draft I give them.

You definitely have to think through the consequences of all your dimensioning choices.

RE: Max & Min Dimensions

(OP)
Thanks everyone... Some valuable info in this thread.

RE: Max & Min Dimensions

Powerhound,
It was all internal to the parent corporation. I worked in the mold shop where we machined the molds for the glass plants to form the product.
We did a lot of fine finish polishing on the molds by hand and these blend radii where part of the hand process.
Once we understood the problem and had inspected the molds, a simple drawing change and instructions to polish guys and the issue was resolved.
 

"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli

RE: Max & Min Dimensions

Assuming you work to ASME Y14.5M-1994 look at section 2.5 "SINGLE LIMITS".

It defines the meaning of Max & Min and gives examples of when to use them.

The issue above where MBD gets involved is significant and has come up in other MBD related threads.

I think max/min has been discussed before too.

As to why to use them, it's to maximize the likelihood of "good parts" while ensuring function.
 

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RE: Max & Min Dimensions

We use min and max here and there on our detail prints. I mainly use them on pockets and cut outs. I place the biggest radius permissible and then put max. reasoning for this is, now the machinist can use what ever size of end mill, or what ever, to make the feature.

Solid Edge V20

RE: Max & Min Dimensions

On some slots here I have seen the end radius called out like this:

4X R.030 MIN TO 2X FULL R MAX

I was confused at first but I figured it out and plan to use it where appropriate in the future. One more exception to my dislike of MIN and MAX.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
www.infotechpr.net

RE: Max & Min Dimensions

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

RE: Max & Min Dimensions

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

RE: Max & Min Dimensions

(OP)
"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.

RE: Max & Min Dimensions

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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RE: Max & Min Dimensions

(OP)
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?

RE: Max & Min Dimensions

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
www.infotechpr.net

RE: Max & Min Dimensions

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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RE: Max & Min Dimensions

(OP)
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.

RE: Max & Min Dimensions

(OP)
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.

RE: Max & Min Dimensions

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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RE: Max & Min Dimensions

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

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