cross drilled hole in tube

[Mike2410]

If the current ANSI 14.5 drawing standard is applied, would a cross drilled hole that extends entirely though a hollow bar (tube) be interpreted correctly with simply a hole size speified or should the hole be specified as 2X? Does ANSI 14.5 clearly state that a break in a cross drilled hole (resulting from the tube ID) imply one location?

thanks

 

[pmarc]

On the contrary, if size dimension is the only characteristic specified for interrupted features (regardless whether with or without prefix "2X"), mutual locational relationship between the features is not controlled at all - features (in your case two holes) are considered totally independent of each other. So additional specification is needed to tie them together.

This can be done in a couple of ways:
1. Using Continuous Feature modifier <CF> following hole size dimension or a note "CONTINUOUS FEATURE". See fig. 2-8 of ASME Y14.5-2009. This is new concept in Y14.5. It makes the two holes a single entity. Rule #1 defines maximum material condition envelope that surfaces of both holes cannot violate. With this approach prefix "2X" shall not be specified.

2. Applying positional tolerance with no datum reference inside FCF associated with hole size dimension (this time with prefix "2X"). This would control offset of holes axes. See fig. 7-59 of Y14.5-2009. The positional tolerance may be applied with or without M modifier - all depends on function of the holes. If you specify "0 at MMC" positional tolerance, it would be equal to Continuous Feature modifier application described in point #1.

3. Assigning one of the holes as datum feature A and control the second with positional tolerance to it.

 

[ak762]

Does it make sense if drag dimension lines thru both holes?

 

[pmarc]

Per ASME Y14.5 the extension lines themselves do not indicate a continuous feature (see para. 2.7.5 in '09 edition), so still no relatioship would be defined.