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Diameter Over Pins measurement


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Hello. Normally when we are measuring our sector no-go plug gauges, we are able to get diameter over pins easily with the type that is shown on the right of the picture. Our CMM guy is having issues getting the DOP measurement from the type on the left, and I was wondering if you have any insight as to what might be the cause, and what would have to be done differently between the two measurements.

DOP.jpg

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I'll be happy to share some advice too.

As Keith mentioned, if you can share more info it will help, also this post is more suited for Gear Pro I would say.

At any rate, I have lot of expereince certifying simlar spline gages, Go and No Go plugs.

Regarding the one on the right, typically the outside flanks of the teeth are "relieved".
I have seen gages similar to the one on the left, perhaps it is for a major diameter fit spline,

Could it be the outermost flanks are releived on each side of the gage? If so, there is not way to get an accurate MOW size.
Getting a tooth thickness in Gear Pro may be your best option, but since ithe outer flanks are probably relieved, it could lead to set up issues when it find the tooth, therefore will not find proper CL of the 'good' flank, and possibly not measure the CTT centered, etc.

I suggest getting a slightly larger ball than the MOW specifies, slef-center in each gap on one side and bisect to find the CL of one tooth, from there, (assuming your X+Y 0/0 are coming from a precision ground feature) you can program a nominal point in the tooth at about the pitch radius on the flank (try to probe in normal direction to flank). Do this on both sides to get a chordal tooth thickness. Apply arcTan formula to get Circular Tooth thickness on PD.

You can also ask the manufacturer how they check it...

Good luck.
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Chris,
Thank you for the response. I will talk with him today and see if he wants to respond to this or just have me do it. The plug we are trying to measure is a "Min Actual Setting Master Plug" for setting a variable ring gauge. The calibrated feature is Circular Tooth Thickness, but with all of our plugs we always check DOP as well. We are kind of in an unfortunate situation because the person who ordered all of these plug gauges and understood what they were for is no longer with the company, so when it comes to Composite Go plugs and Sector No-Go plugs, its kind of a no-brainer but we also have a slew of variables as well and sometimes have to dive a little deeper to understand what they are for.

I will get with our CMM guy and see if he can join this conversation. Thank you again.
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We are doing the A measurement. The measurement is 30.7041 +\- 0.0025. With Gearpro, we cant even get data on the left plug type. We took it and ran it on our Marsurf PCV and even there we got 30.539 which is really weird. We ensured we had the correct pin size (1.8mm). We even tried the manual DOP measurement with pins and a mic and that got us closer but still came up short at 30.697-30.701. Our CMM guy said he is going to try and scan the flanks to see if maybe that will provide enough data to get some numbers
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For me, using the Tangent function is usually more repeatable than Circle in contour fit (Circle in countour sometimes fails to generate data for me); but my preference is to order styli that match the prescribed pin diameters, and this method has never given me issues. I believe ITP Styli had 1.8 as a standard selection (or at least in stock at the time that I ordered them)
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  • 1 year later...
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I wanted to revisit this topic as I found something out. It looks like for this, we dont need the DOP. We need the Circular Tooth Thickness since that is what this setting master is made for. The only downside is that it only has one tooth on each side. Our CMM guy is saying that maybe its not giving him enough data because it is not measuring correctly. Are there any recommendations to achieving this circular tooth thickness?
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Jason,

I've done this hundreds of time in Gear Pro on same sector plug spline gages.

It is possible to get an accurate reading.

My way of doing it is very long to explain - have you had rotary table training and/or gear pro training?
I'd suggest start there - they will even likely help you measure this at your facility.

I may be able to help program and with instructions for a charge - it's worth it - PM Me. Thank you.

Good Luck
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