Buttress Thread Help Measuring

[metx]

Hello all,
Could someone please help me with measuring an American Buttress 45/7
OD thread?
The thread data: 6-3/4"-3N Buttress-2ASA, RH
Major diamer 6.7267-6.7407"
Pitch Diamter 6.5934"-6.6074"
Minor Dia. 6.343"-6.4034"

I need to know what size wires and measurment over the wires for PD
I came across a formula online the find best wire size and come up with
.18049" Can this be verified also.
Thank you for any help.
Metx

 

[Gordon B. Clarke]

This is what I can come up with for your thread. The wire diameter is about the only thing that looks the same.



This is how I measure pitch diameter on Buttress threads:

http://flexible-measuring.com/images/thread_inserts/04_Buttress Thread Measurement.pdf

Home

 

[metx]

Thanks Gordon,
I don't know why the data on the print I have is different from standard size. I have a sample part and will measure PD on it with .180" wires and I guess make the new parts to match it or a little smaller.
If I had a lot of threads like this would check into FMS system. I been on their website checking them out. Nice and seems affordable way to measure with out expensive gages.
Thanks,
Keith

 

[Gordon B. Clarke]

Keith,

Any chance you can post a picture (when you're finished) of what you're making that uses that thread?

Buttress threads fascinate me. If I remember correctly it was a Texan that got me started on them

Gordon

Added: My memory is correct Buttress threads have turned out to be more used than I thought. Most are 7º/45º.

 

[mrainey]

6-3/4"-3N Buttress-2ASA, RH

I haven't seen 3N or 2ASA on a blueprint before, and can't find them in the standard or by using Google. If it was my job, I'd be on the phone to the customer. It could even have a modified thread form.

 

[Gordon B. Clarke]

6-3/4"-3N Buttress-2ASA, RH

I haven't seen 3N or 2ASA on a blueprint before, and can't find them in the standard or by using Google. If it was my job, I'd be on the phone to the customer. It could even have a modified thread form.

Probably shouldn't have but I took the 3 to be TPI (looked plausible from the diameter) and the 2A as the tolerance. It was an external thread and 2A is an external tolerance.

Buttress-2 ASA - Google Search

Seems to be an old type Buttress thread.

Screw-thread Standards for Federal Services, 1957 - United States. Interdepartmental Screw Thread Committee - Google Boger

You're right. Not wise to start before contacting the customer. Even a 7º/45º Buttress thread has profile variations. Same with Stub Acme - more than one standard. Not a problem I have as what I make measures only pitch diameter.

Re Stub Acme then ½ height Acme is the most common but there are also 1/3 and 1/4. ASME/ANSI B1.8

Mike, you must be as daft as I am to be just as interested in threads as I am

 

[mrainey]

Probably shouldn't have but I took the 3 to be TPI (looked plausible from the diameter) and the 2A as the tolerance. It was an external thread and 2A is an external tolerance.

Likely all true, but we both know better than to assume anything. The oddball diameters and designations might well be accompanied by other "special" features.