1.00"-20 thread ring pitch diameters

rockfish · Jan 28, 2010

Can anyone tell me what the Go/Lo pitch diameters for Class 2 and Class 3 (1.00"-20) thread rings are ???

Thanks,

Frank

www.randolphmach.com

hdrider63 · Jan 28, 2010

Hi Frank,

On a 1"-20 UNEF thread the max pitch diameter is .9661 and min. is .9616 for class 2 threads. For a class 3 thread it is max .9675 and min. .9641 diameters. Minor thread diameters for a class 2 is.9391 and for class 3 it is .9405 ....

Jeff

rockfish · Jan 28, 2010

I have a set of rings that are .9675/.9578

I need to check a class 2 thread, so it looks like these aren't going to work.

Forrest Addy · Jan 28, 2010

What standard are you held to? Are you required to ue calibrated functon gage? Are your gages in calibration? Is the No-Go adjustable so it can be tweaked?

Can you use the 0.9578 PD No-Go as a fitting gage where you determine fit by checking radial clearance with a dial indicaor? You can validate the dide play method with a cross-check over thread wires for the first few parts then move on to the ring gage check alone.

SND · Jan 28, 2010

Just 3 wire it?

hesstool · Jan 28, 2010

SND said:
Just 3 wire it?

x2. Simple solution.

rockfish · Jan 29, 2010

I have a full set of thread mics to check the thread. No need for wires (but I have them too).

I've addressed this issue before in other posts without ever hearing a satisfactory answer.
I have, many times, checked a thread thoroughly with thread mics and found it to be perfect, only to find that the thread rings won't go on. In order for the rings to go on, generally you have to run your thread down to low limit or slightly under low limit.

Most of my military customers insist on the parts fitting the thread rings. They don't care what they mic, as long as the Go/No Go rings work correctly.

Frank

www.randolphmach.com

Forrest Addy · Jan 29, 2010

rockfish said:
I have a full set of thread mics to check the thread. No need for wires (but I have them too).

I've addressed this issue before in other posts without ever hearing a satisfactory answer.
I have, many times, checked a thread thoroughly with thread mics and found it to be perfect, only to find that the thread rings won't go on. In order for the rings to go on, generally you have to run your thread down to low limit or slightly under low limit.

Most of my military customers insist on the parts fitting the thread rings. They don't care what they mic, as long as the Go/No Go rings work correctly.

Frank

www.randolphmach.com

Which is the whole point of functonal gaging. The sum of the many threading errors possible in single point tooling screw threads often result in wide discrepancies between size over wires and pass/fail with fnctonal gages. Tri-lobing in work held in three jaw chucks for example. Tool pull-in on the first thread. Drunken lead. It's a minefield.

Screw threads have to be made to almost gage precision for the size over wires to agree with the size inferred by full form enveloping of functional gages.

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1.00"-20 thread ring pitch diameters

rockfish

Titanium

hdrider63

Aluminum

rockfish

Titanium

Forrest Addy

Diamond

SND

Diamond

hesstool

Stainless

rockfish

Titanium

Forrest Addy

Diamond

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