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SDETERS (Agricultural) (OP)
18 Feb 11 15:00
Looking at an Inch print using ASME Y14.5-1994 specifying an angle of .50 degrees.

Does one use a leading zero or not on this dimension?  0.5 degrees or .5 degrees

Thanks

 
Helpful Member!  lifttrucks (Mechanical)
18 Feb 11 16:00
This may or may not help you, but the 2009 standard added wording to the end section 1.5.5 stating that "Where decimal degrees less than one are specified, a zero shall precede the decimal value."

This wording was not in the 1994 standard that I am aware of.

If you look at figure 2-2 in the 94 standard, it does show a tolerance of -0.2 degrees with a leading zero.
Helpful Member!  pmarc (Mechanical)
18 Feb 11 16:02
Leading zero should be omitted.

Number of trailing zeros depends on a tolerance for this angular dimension. Generally saying - both dimension and tolerance must have the same number of digits after decimal point.
SDETERS (Agricultural) (OP)
18 Feb 11 16:02
Great that is what I was looking for.  

Thanks
pmarc (Mechanical)
18 Feb 11 16:05
There should be "should not" in the first sentence of my post.
Helpful Member!  SteveMartin (Mechanical)
18 Feb 11 16:12
As far as I can tell Y14.5-1994 is silent on this question.  I would be inclined to go without the leading zero, just for similar look to any linear dimensions less than one.  I'd say either one would be 'legal'.  If it's a common situation for your company I'd say it should go in a company standard.
Helpful Member!  MikeHalloran (Mechanical)
18 Feb 11 16:15
I'd be inclined to use a leading 0 because the decimal point is easy to miss.

 

Mike Halloran
Pembroke Pines, FL, USA

SDETERS (Agricultural) (OP)
18 Feb 11 16:36
The Angle Dimension I have looks like .35`+/-.15`

This looks really close to .35+/-.15.

So we usually look to the next standard if the Current one does not answer our questions.

Thanks again for all the feedback
pmarc (Mechanical)
18 Feb 11 16:44
According to Y14.5-2009 (paras. 1.5.5 & 2.3.3) it should be:
0deg35' +/- 0deg15'
 
CorBlimeyLimey (Mechanical)
18 Feb 11 20:19
pmarc,

Does Y14.5-2009 (paras. 1.5.5 & 2.3.3) really show the angle using mixed unit symbols? (deg and '), as opposed to 0°35' ±0°15' ?
pmarc (Mechanical)
19 Feb 11 2:17
By typing "deg" I meant degree symbol - I just did not realize that there is a possibility of putting 0 superscripted in the post. Sorry if this made any confusion.  
CorBlimeyLimey (Mechanical)
19 Feb 11 9:10
There are many TGML characters and formatting codes listed at the Process TGML link below the reply box.
http://www.tipmaster.com/includes/charentities.cfm

You can also use the standard Alt key method;
Alt 0176 = °
Alt 0177 = ±
DeanD3W (Mechanical)
19 Feb 11 10:46
The title of this thread seems to allow the question that I'm about to ask, but with the discussion being about leading zeros, just tell me to go away and stop hijacking the thread if I'm off base...

What about the fact that a directly toleranced angle is very likely ambiguous and/or not providing the control that the part's function requires?  If the considered feature is a planar surface then there is no tolerance zone for such a spec other than 4 lines drawn on a 2D cross-section of the feature that define min & max angles.  If the considered feature is cylindrical then what is the controlled feature component and what is it controlled relative to?

For drafted features all the same issues apply.  We've all seen direct tolerances applied to draft angles, but "relative to what measurable element/reference frame?" is the unanswered part of those specs.

Since this is a GD&T forum it seems appropriate to bring up the fact that the directly toleranced angle being discussed should be replaced with a basic angle from a plane or axis of a datum reference frame that is included as part of a position or profile call-out...  Yes?  No?  smile

Should I have started a new thread?
MikeHalloran (Mechanical)
19 Feb 11 20:16
GD&T is not _all_ this forum is about.
Whether to use GD&T is a separate discussion.

One other extraneous point that's a little closer to the core of the discussion is that it will almost certainly be necessary to include a synthesized view with the angle exaggerated, in order to make any sense of the direction of a small angle.

 

Mike Halloran
Pembroke Pines, FL, USA

Belanger (Automotive)
19 Feb 11 22:03
Hi Dean -- I'm not sure what you mean by the 4 lines, but there is indeed some baggage that comes with a directly toleranced angle.   One issue is that a ± angle tolerance will yield a widening zone as you go further out from the vertex.  This is not illegal, but something to be aware of (and thus, form of the surface is not controlled).   Also, how do we know which "leg" of the angle gets the tolerance?  If I see a drawing with 45º ± 1º I might measure that ±1º as being on the base leg, where another person might think of the tolerance as being on the other part of the 45º -- and there are times when it could make a difference.

I think that's along the same lines as your comment, so yes I agree!

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

SDETERS (Agricultural) (OP)
21 Feb 11 10:59
Please see example for what is getting dimensioned.

I made the drawing more simple just to show the feature in question.  I see how a profile of surface could be used instead of of a directly dimensioned angle with a +/- dimenion.  The r2.0 is there to show the cross section go through a circular area of the part

Thanks



 
lifttrucks (Mechanical)
21 Feb 11 11:41
SDETERS,

Since you are using The Y14.5 standard, may I suggest you relocate your datum feature symbol B. The standard states that datum feature symbols identify physical features and should not be applied to center lines, planes, or axes.

The problem for manufacturing/inspection is how do they know which feature the center line/plane is referring to.

I would also consider Mike Halloran's point - how do they know which way the angle goes? Is it tapered up, or down? You may have to exaggerate the angle or clarify with a note.
SDETERS (Agricultural) (OP)
21 Feb 11 11:49
The B datum is specified somewhere else on the print.  B datum is a feature on the print.  I did not show the entire print.  I want to make sure the angle is dimensioned from the datum B plane.

The angle direction should be implied.  This part comes off a mold and for this to happen the draft can only be in one direction because the if it was the other way the tool we would crash.

Good points and also thanks for the feedback.
PeterStock (Mechanical)
21 Feb 11 13:00
If you dimensioned the angle from A instead of B it may be clearer.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
www.infotechpr.net
http://www.linkedin.com/profile/view?id=30064526&trk=tab_pro

pmarc (Mechanical)
21 Feb 11 13:07
SDETERS,

If you have access to ASME Y14.8-2009: "Castings, Forgings, and Molded Parts", section 3.6 specifies different methods of assigning draft angles. Maybe you can find something interesting for you.

'Directly toleranced angle' method is not among them mainly because of all the reasons that Dean and J-P highlighted.  
DeanD3W (Mechanical)
21 Feb 11 16:13
Sorry to be vague regarding the tolerance zone consisting of only four lines on a 2D cross section of a feature.  I pulled a slide from training material to better explain what I meant (which I think will indicate that J-P & I are agreeing on this).  Please see the attached file.

I'm sure I will rightfully hear about it if I'm incorrect with the assertions I'm making in the file smile.

Dean
www.d3w-engineering.com
Belanger (Automotive)
21 Feb 11 18:12
Hi Dean -- thanks for posting the picture.  Are you sure you want to say that splitting the tolerance to both sides of the wedge is the only possible depiction?  

I'm not disagreeing; I'm just thinking out loud...  what if someone tries to arbitrarily call one side of the wedge an implied datum and then tries to scrunch all the angular tolerance onto the other side of the wedge?

I'm not saying that's wise, because a datum can only be made from high-point contact and thus we can't know the form of that "datum" side.  But is an angle with a ±tolerance really meant to control form?

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

DeanD3W (Mechanical)
21 Feb 11 20:24
Hi Jean-Paul,
I think you could say that someone may try to scrunch all the angular tolerance to one feature & use the other as a reference surface.  I don't think they have any standard to back up what they're doing, so maybe that's the same situation as splitting the tolerance equally on both sides smile.

Since we have no standard to define a tolerance zone for directly toleranced angles I don't think form can be considered controlled this way...  I can imaging features which both have horrible form, but with best-fit lines (one for each feature) at a given cross-section having an acceptable angle between them, I think a supplier could declare the feature to be in spec.

I think it's quote odd, in a bad sort of way, that so many drawings have default tolerance blocks with +/- angle tolerances included.  These tolerances don't really mean anything, er, I mean, they may mean several things.

Dean
www.d3w-engineering.com
Belanger (Automotive)
21 Feb 11 20:44
Yes -- I agree, and think that your last paragraph sums it up!

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

DeanD3W (Mechanical)
22 Feb 11 1:29
Wow - As I look back at my last post, those typo/spelling issues seem to be getting me "quote odd" rather than "quite odd", and "imaging" instead of "imagine".  Sorry everyone :-\.  Too bad a post here can't be edited.  Good thing I'm not doing any drawings tonight...  That could be ugly smile
KENAT (Mechanical)
22 Feb 11 14:55
If you red flag the post and let management know the required change, they will sometimes edit for you.

DeanD3W, you make a valid point, but I wonder if you're over stating it a little.  

Certainly for critical stuff with angles I tend to use profile and encourage others to do so.  However, I'm hesitant to completely throw out +- dims on angles but maybe I'm pandering to the 'GD&T is too complex/costs money' crowd.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

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