How To Verifying a Thread gage ?

[allloutmx]

How would one verify an OD thread gage?
Im affraid my turkish lathe buddy is about to have a bad day

 

[sfriedberg]

I'd send it off to a calibration lab, or to a thread gage manufacturer, for calibration and assessment.

 

[AARONT]

What type of gage?

 

[allloutmx]

What type of gage?

adjustable ring ...class 2b thread

 

[6spindle]

Master plug gage or send it out for calibration would be the best way. If you have a known good part you could compare to get you in the ballpark or skip the gage and measure the part directly using the 3 wire method.

 

[Gordon B. Clarke]

adjustable ring ...class 2b thread

Huh? a Class 2B thread is an internal thread. You can't use a ring gauge for that. What is the thread diameter and pitch you want to use your adjustable ring gauge to check?

 

[allloutmx]

Huh? a Class 2B thread is an internal thread. You can't use a ring gauge for that. What is the thread diameter and pitch you want to use your adjustable ring gauge to check?

Correct, my mistake.. It is a 1/2-20 2A thread.

 

[Gordon B. Clarke]

Correct, my mistake.. It is a 1/2-20 2A thread.

It's a ½" UNF thread. Your max pitch diameter should be 0.4662" and min 0,4619".

Probably cheaper (and better) to measure the pitch diameter on the components or components with thread wires or similar. At least then you'll know exactly where you are.

The diameter wires (if you choose this method) you'll need are 1.27mm or as close to that as possible. The alternative is sending your ring gauge to a calibration facility and it'd probably be cheaper buying Go NoGo thread ring gauges. It is after all a standard thread. Of course if your adjustable ring gauge needs to be set to an "unusual" pitch diameter because of the component or components being surface coated after machining then that's another matter.

Asking questions is usually cheaper than making mistakes

Gordon

 

[allloutmx]

It's a ½" UNF thread. Your max pitch diameter should be 0.4662" and min 0,4619".

Probably cheaper (and better) to measure the pitch diameter on the components or components with thread wires or similar. At least then you'll know exactly where you are.

The diameter wires (if you choose this method) you'll need are 1.27mm or as close to that as possible. The alternative is sending your ring gauge to a calibration facility and it'd probably be cheaper buying Go NoGo thread ring gauges. It is after all a standard thread. Of course if your adjustable ring gauge needs to be set to an "unusual" pitch diameter because of the component or components being surface coated after machining then that's another matter.

Asking questions is usually cheaper than making mistakes

Gordon

is three wire going to be more accurate than using pitch mics?

we have already measured the parts as such... maj dia and pitch and pitch dia...thread gage wont go so I was hoping for my friends sake, it was the customers ring gage. Thats why I was wondering how I could verify the gage is right/wrong and not measuring the part itself.

 

[Gordon B. Clarke]

is three wire going to be more accurate than using pitch mics?

we have already measured the parts as such... maj dia and pitch and pitch dia...thread gage wont go so I was hoping for my friends sake, it was the customers ring gage. Thats why I was wondering how I could verify the gage is right/wrong and not measuring the part itself.

The 3 wire method is generally considered the most accurate pitch diameter (affordable) measurement method. The problem with both wire and pitch diameter mics is that they both "assume" correct flank angle. The more the flank angle is "off" (in this case 60º) the greater the discrepancy will be. If you have a shadow graph or microscope check the flank angle on your component.

I've already given you the thread pitch diameter tolerance so if you let me know what you measured the pitch diameter to be that'd help solve the "mystery"

Nominal pitch diameter for ½" UNF is 0.7175 and max pitch diameter for 2A is 0.7162 so there is an allowance of 0.0013 to make sure that they are apart even with the smallest internal thread and largest external thread.

Gordon

 

[allloutmx]

chipped insert...thread form was off..one side of the thread looked good, the other does not.
Gage, im assuming is fine, but Would still like to know, how to verify...send it out to calibration...okay..how to "they" do it?

 

[Gordon B. Clarke]

chipped insert...thread form was off..one side of the thread looked good, the other does not.
Gage, im assuming is fine, but Would still like to know, how to verify...send it out to calibration...okay..how to "they" do it?

They measure with balls the same diameter as the wires they would use if it was for external.

A set of Go NoGo thread ring gauges for your ½" thread would probably cost you from USD $200 and up. You can compare that with calibration costs.

Question: I understand the "adjustable" ring gauge is supplied by the customer. If it's adjustable they should be able to tell you what they calibrated it to.

For "state of the art" look at this http://www.youtube.com/watch?v=jjdTrlY8io4

 

[Nick Mueller]

What exactly do you verify on that gage?
Pitch diameter? Pitch? root diameter? Root radius? Outer diameter?
Depending on what you want to verify, it can go from "quite easy" to "very complicated and expensive".


Nick

 

[Gordon B. Clarke]

Are you sure nominal pitch diameter for a 1/2" UNF is .717?

LOL A page on my standard flipped over so I looked at 3/4" UNEF - 20 instead. They're both the last one given except ½" is on bottom of page 25 and 3/4" on the bottom of page 27 of ASME B1.1 It is of course 0.4675 so I'm left wondering why you didn't just write the correct nominal pitch diameter while you were at it.

At least what I had written was off by so much it was obvious it was wrong.

Still, thank you for your help