What if I don't specify "R" on an Elongated Hole (or Slot)? 1

[jmarkus]

Page 126 (Figure 7-34) of ASME Y14.5-2009 shows that to control the boundary of a slot (also referred to as an elongated hole), you call out the size and position tolerance in each of the directions of interest. It also shows that the radius is noted (although not dimensioned or toleranced) by "R". What happens if "R" is omitted? Does the interpretation change, even if the drawing shows a radius? Does this mean the rectangular slot can become a rectangle with sharp corners? Why isn't there a tolerance or size provided for R? Is it correct, ambiguous or redundant to specify one?

Thanks,
Jeff

 

[KENAT]

What happens if "R" is omitted?

The drawing is incomplete and hence ambiguous. An argument could be made that in this case a rectangular 'slot' with sharp corners is actually what the drawing dimensions define. So there is a potential conflict between the drawn geometry and the stated dimensions. If the machine shop picks the wrong one you get bad parts that "legally" you may not be able to reject.

Why isn't there a tolerance or size provided for R?

The size/tolerance for the 'R' in a elongated hole is defined by the width dimension & tolerance - the use of 'R' means is it is a full R derived from the width of the slot.

Take a look in section 1 where it initially talks about rounded ends. I don't have 2009 edition but in ASME Y14.5M-1994 it's section 1.8.4 & figure 1-27.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[ewh]

Same in 2009, except now fig. 1.29

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