【转帖】correct obround definition

yang686526

correct obround definition
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?
powerhound
production supervisor
inventor 11
mastercam x2
smartcam 11.1
ssg, u.s. army
taji, iraq oif ii
depends how it's made. is it a punch in sheetmetal or machined?
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
chris,  does it matter how its made?  processes are technically not called out on drawings in most cases.  
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
matt,
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
chris,  powerhound described an external feature that would normally have to be machined (unless a sheet metal form).   
matt
cad engineer/ecn analyst
silicon valley, ca
ctopher,
   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
drawoh,
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
i'd probably go with overalls and 2x r (plus height probably in another view).
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...
  sorry for the delay in posting back. i had a death in the family and had to go out of town for the weekend.
  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
sorry to hear about that powerhound.
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. 鈥?br />
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...
kenat,
  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