Thread Depth Specifying - Sanity Check Requested 3

[KENAT]

When specifying the depth of threaded holes I got in the habit some time back of usually specifying something like:

“… .25 MIN FULL THREAD”

or

… “.125 MIN FULL THREAD DO NOT BREAK THRU”

Unless function requires a maximum as well as minimum depth.

To my mind this meets the real functional requirement without requiring extra inspection to check the max full thread depth. I find this especially useful as when using automatic call outs our CAD system puts the thread depth to the same no. decimal places as the thread diameter, so if you have a 3 DP hole dia (as is typical) you by default end up with 3 DP depth, which on our tol block is +-.005 so is rarely warranted. To change just the depth to 1 or 2dp you have to make the dimension non associative (or have some other kluge) and even then I’d think it rare that +-.010 or +-.030 is really required.

Also if I have a hole that goes from a face and intersects with another hole (common here as we have quite a few pneumatic manifolds or similar) I’ll say something like:

…THRU TO Ø.201 HOLE

I just had a designer argue both of these with me, his main objection being that these notes take up too much room (this on an E print). When I said about putting max/min increasing inspection he countered that we don’t inspect this stuff anyway. While probably true I find it a poor argument, especially as we are moving to outsourcing to different vendors (as mentioned in previous post) where inspection may become more significant. Obviously on the holes that go thru to another hole, there isn’t usually a hole depth left to measure.

So, any thoughts on if I’m right, he’s right or there’s some better way I’m missing. Please don't get hung up on our ridiculous inspection situation, though of course it is pertinent to a point.


KENAT, probably the least qualified checker you'll ever meet...

 

[KENAT]

kbro, this is covered by ASME Y14.5M-1994 1.4e "However, in those instances where manufacturing, processing, quality assurance, or environmental information is essential to the definition of engineering requirements, it shall be specified on the drawings or in a document referenced on the drawing.”

KENAT,

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

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

 

[fcsuper]

kbro,

I agree with KENAT's statement, however I have a comment for you. Why would you specify roll vs. cut? The end result is the same. Let the vendor work it out as to which method is best. I can imagine scenarios where roll is a much, but these are extremely rare in my opinion.

In either case, do not callout the drill size. Simply call out the thread spec. If you need to mention the process, then do so (without the drill size). The final ID of the thread is already specified by the thread callout itself.

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group

 

[KENAT]

Just re-read kbro post and I agree with Fcsuper that while you may use different tap sizes based on process that probably isn't what you should specify on the drawing. You should explicitly specify 'rolled' or 'cut' if you require it.

I know there are situations where rolled are (were?) preferable to cut threads.

KENAT,

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

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