Showed on drawing

[lehai]

Please help to advise me as following:

On drawing showed that: Dia..159 Tap thru 10-32 UNF. What does it mean? the hole is drilled or threaded?
thanks

 

[ewh]

It seems that both the pilot diameter and the thread are being called out. This is poor practice, and should only specify the thread (10-32 UNF THRU).

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[ewh]

There can be exceptions though, such as when the size of the pilot hole is more critical to the function of the feature than would be achieved using standard sizes.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[KENAT]

Agree with ewh, is there a separate depth given for the 10-32? If the tap drill was through used as maybe a vent hole or access or something, and the thread is almost like a counter bore (really a counter drill) then it may be valid to give the tap dia (although it still shouldn't say "tap", it should just be dimmed as a counter drill) however the depth of thread should be specced.

Also the thread call out is incomplete, it doesn't give a class.

Sounds like it may be a poor drawing, can you go back to the customer/designer?

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

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

What is Engineering anyway: faq1088-1484

 

[dinjin]

That is common in house detail designation to list the
tap drill as well as the thread size. I am surprised that they did not call out the 10-32UNC-2B or 10-32UNC-3B
designation. So they are telling you to drill thru and then to tap thru after drilling.

 

[KENAT]

dinjin, guess ewh/I should have said that per ASME standards you don't normally give the tap dia - generally you spec the finished article not the process.

I've seen/heard the arguments about listing tap drill on manufacturing plans or drawings that double as them.

The fact the above question came up is perhaps a reminder of why there are industry standards.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

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

What is Engineering anyway: faq1088-1484