Report Gear and tooth thickness

[[Fr...]]

Hello all,

I have a doubt about a topic.
We are measuring an internal gear with module 0,72, using a diameter probe 0.8mm.
I have a report (attached) where MDK is ok, Rooth Diameter is ok..ecc;
The only value out of tolerance is tooth thickness.

What could be the reason? 😕

Thank you in advance for help.

report1.pngreport2.pngreport3.png

[[Ma...]]

It looks like you measured space width, not tooth thickness. Is there a chance you entered the tooth thickness tolerances for space width? This would explain your result.

I can correlate the tooth thickness, space width, dimension between rolls etc. for you if you provide number of teeth, pressure angle and helix angle in addition to the normal module you already provided.

[[Fr...]]

Thank you for the answer.
Yes it's my fault, we are measuring space width and using max effective space tolerances Ev.

The internal gear has these characteristics:
z=32 m=0,72 Pressure angle= 30° helix angle = 0° x= -0,1472

[[Ma...]]

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I calculate that 20.981 and 21.058 between 1.4 mm balls correlates with 1.2535 and 1.294 normal circular space width. Also, correlates with 0.968 and 1.0085 normal circular tooth thickness. "Effective" tooth size specifications should not generally be used for spline size measurements on a CMM.

[[Fr...]]

So you think there is an error in the Max effective space tolerances?

Why max effective space should not be used for measurement?

[[Ma...]]

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To tell you the truth, I didn't even know that "effective space width" was an option in Gear Pro. This value is usually used to manufacture the Go gage as it includes allowances for all the other deviations, pitch, helix and profile that would influence the fit. Seems like a tall task to perform with the limited information available from the CMM but I have no experience with this to.

[[Ky...]]

Hello all,

First a response to Mark. Yes GEAR PRO now supports minimum and maximum effective tooth thickness. This functionality was added in either GEAR PRO 2019 or 2020, I'm afraid I can't remember which one right off the top of my head I'm afraid. To calculate it, you need to add an item to the measurement run specifications called "Gauge Evaluation", in the same place you put the lead, profile or pitch. It takes the data from all of those measurements (at least the ones you did) to calculate it.

Second, to Franco, how was the addendum given in the print? Was it as a dimension over pins or did they just give you the addendum coefficient by itself? I have seen situations where whoever makes the print gives a value for the dimension over pins that doesn't work with the tooth spacing they give before.

Best regards,
Kyle Johnson
Applications Engineer
ZEISS Industrial Quality Solutions

[[Ma...]]

Thanks for the information Kevin. I read up on this in the manual. It looks like fairly extensive measurements are required for reliability for this evaluation. For example, multiple profile measurements on every tooth along with helix measurements on every tooth and pitch measurements. This seems like it would be quite time consuming for a CMM with a tactile sensor. Maybe significantly faster with laser based measurement? Either way it seems like a nice option for small batch production.

[[Fr...]]

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Thank you for the answer.

They give me addendum coefficient=0,45.

In any case could you explain me better the difference between "max effective space" and "space width"?

[[Ed...]]

Here you can find good explanation:
https://gearsolutions.com/features/actu ... ooth-size/