Countrsink lead-in for internal threads--is there a std?

[wgchere]

I'm looking for a standard or information regarding the countersink on an internal thread.

I have an engineer who insists on specifying a countersink on all internal threads. I have contended that it is standard machine shop practice to put a 90° csk as a lead-in (he always specifies 120°) a little larger than the major dia.

"Prove it!" he said.

I thought I had seen it in Machinery's Handbook, but I couldn't find it, and a search of several hours and many keywords turned up nothing--except this site, which I had never heard of before.

Anyone have any info/ideas?

Thanks,
WGC here.

 

[wgchere]

What chart is that, Metalart?

 

[METALART]

Give me a little time to come up with the origin of this, I use a copy of all this info that an inspector put together, great sheet, I remember him saying it took him quite some time to get all the info because it was not readily available. I could fax you a copy right now if you want. This guy is good and fussy so I new it was /is good info.

 

[tbuelna]

Take a look at MIL-S-8879 or FED-STD-H28.