Correct obround definition
Correct obround definition
(OP)
Heelo all,
I have a question regarding how to define an obround. The ASME standard shows how to define a slot by using a slot width and a "2X R" to define the ends but would this also apply to a "male" feature? We have this exact situation where an OD is dimensioned with the fully radiused ends and the "2X R" is used to control the end radii.
Any input is appreciated?
I have a question regarding how to define an obround. The ASME standard shows how to define a slot by using a slot width and a "2X R" to define the ends but would this also apply to a "male" feature? We have this exact situation where an OD is dimensioned with the fully radiused ends and the "2X R" is used to control the end radii.
Any input is appreciated?
Powerhound
Production Supervisor
Inventor 11
Mastercam X2
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II





RE: Correct obround definition
For machined, I think I may use width, length, height and "R FULL".
Can you show a pic?
Chris
SolidWorks 07 3.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 04-21-07)
RE: Correct obround definition
powerhound,
I would just dim the final required size. In the case of the OD ob, I would likely dim the overall length (max radius), and the two radii as 2X R(number).
Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group
RE: Correct obround definition
If it's punched or pressed or ?, I would dim as you mention.
If machined, the machinist will need height and full radii dim.
Just the final size, not the process.
Chris
SolidWorks 07 3.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 04-21-07)
RE: Correct obround definition
Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group
RE: Correct obround definition
I do not think that "R FULL" is used anymore. I am pretty certain that it does not occur in the ASME standard.
The standard shows several ways to dimension and tolerance this shape. For internal and external forms, I usually dimension to the outside of the radii. This makes it easy to do a quick and dirty inspection with calipers.
I suspect the 2 X R notation is used to eliminate redundancy. If the slot is 6mm wide, the radii must be 3mm. On a hand drawing on a drafting board, someone might update the 6mm, and miss the radii. This is a valid issue for internal and external forms.
JHG
RE: Correct obround definition
You're correct.
I need to blow the dust off my ASME books. I have not looked at them in two years.
Chris
SolidWorks 07 3.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 04-21-07)
RE: Correct obround definition
Like some others from the point of view of dimensioning scheme for the shape I don't see what difference it really makes if it's male or female feature.
KENAT, probably the least qualified checker you'll ever meet...
RE: Correct obround definition
Thanks for the comments. I suspect that the ends of an OD should be dimensioned the same as a slot (ID) but the standard doesn't specifically address it that way so it provides a loophole for argument. I was trying to get either opinions or even a direct reference as to how this should be handled because it makes a difference in whether or not the parts we have are good or not. Actually it doesn't make a difference because the parts are already dispositioned as rejects but I'm trying to determine whether or not my argument was valid. From what I've read here my argument was valid. My contention was that the "2X R" callout was valid and their (QC) contention was that it was not.
Thanks again for the input.
Powerhound
Production Supervisor
Inventor 11
Mastercam X2
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
RE: Correct obround definition
Sorry to restart an oldish thread but I was looking for something in ASME Y14.5M-1994 the other day and found:
1.8.4 Rounded Ends. Overall dimensions are used for features having rounded ends. For fully rounded ends, the radii are indicated but not dimensioned. See fig. 1-27. …
1-27 Shows an obround dimensioned by total width, total length and 2X R.
It makes no distinction between female or male features.
KENAT, probably the least qualified checker you'll ever meet...
RE: Correct obround definition
It's funny, I just found that paragraph last week too. It was while I was studying for my upcoming test. Thanks for posting in case I hadn't found it yet.
Powerhound
Production Supervisor
Inventor 11
Mastercam X2
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II