Bolt Circle as a Datum in FCF

[[Su...]]

How do I set up a (3 hole) Bolt Circle as the secondary datum? The FCF is True Positon of a hole dia.@MMC to a plane and bolt circle @MMC. TIA

[[Ri...]]

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You will need to create the Bolt Circle first.

If you measured the individual bolt holes as circles, just drop in a blank Circle from Features - Circle. Then open the Circe, drop down in the middle where it says Options, select Recall (do not select Recall Feature Points), and select all three of your individual Circles. This will create a Theoretical Circle that goes through the center of each of your individual Circles.

If you measured the individual bolt holes as cylinders, I would suggest intersecting them with the face that they meet with first, then the steps are the same as above.

Good luck.

Thanks.

[[To...]]

Without seeing the drawing, I'm guessing there is a position for the 3 holes, which then referred to as a datum feature. This would require create a Best Fit Bore Pattern Position. Can you post a screenshot of the callout from the drawing or create a quick sketch if you can't post any part specific pictures?

[[Su...]]

Quick sketch attached. Thanks so much for the set-up help guys! This is a base plate and the bolt circle holes attach to rubber grommets. I'm struggling with the FCF. Also,I don't understand why the TP would go to Datum-B- instead of Datum -C-? If someone experienced could explain it to me, TY!

Example.png

[[Ri...]]

Yes - this is what Tom said. Datum B is the Best Fit Bore Pattern of the three holes.

Once you perform the Best Fit, you will have access to use that alignment created for other Position/Profile characteristics.

[[Su...]]

So the best fit alignment is what I need to do and this will cover MMC also? I need to check the best fit alignment out. Thanks!!

[[To...]]

Your sketch is NOT what I was envisioning. I was expecting to see the 3 holes to be positioned to A only, which the Best Fit Bore Pattern would be used for to establish datum B. I don't see what C does for you.

Do they only want 1 hole for datum B??? This is not good GD&T, imo.

[[To...]]

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After you select the 3 cylinders/circles, you'll set the Best Fit to "With MMC/LMC of References". Tick Rotation and Translation setting.
This will allow you to select MMC on the secondary datum (B)

Then, if there any other positions that refer to A and B, you'll choose the Best Fit Bore Pattern alignment instead of selecting A and B.

This could a bit more complicated that I am making it sound only because I cannot see the entire drawing.

[[Su...]]

Sorry, rough sketch. Richard and Tom, thanks for your time. It took a few to figure it out but I finally got it. 🙂 You guys turned Monday#2 into a Tuesday!!

I just wanted to show Datum-C-(Bolt Circle) was separate from Datum-B-(3 bolt holes).