Hi

I have attached a picture of a part that I hope can be seen.

the small OD on the left and right sides are dat -A-'s. I measure 3 circles with 6 points, one circle at the begining and end of the cylinder and one in the middle of the cylinder and I do this on both dat -A- cylinders on the left and right sides and then construct center points on those circles and construct a 3D line through those points and use that line as my dat -A-. My supplier takes one circle with 5 points on each cylinder then constructs a 3D line through those two circles and uses that line as dat -A-.

The ID cylinder facing the operator in this view is one of two cylinders, there is one on the opposite side and these cylidners are dat -B-. I do the same with those cylidners, I measure 3 circles on each cylinder and create a 3D line and use that line as my dat -B-.

My supplier is only measuring one of those dat -B- cylinder and using that as dat -B-.

After I contruct my 3D lines, I create a intersction point, axis origin to that point and rotate my axis to lines. In my opinion, I have just set a fairly accurate axis on my part to the datums and I can begin measuring all my features and dimensioning them.

My questions:

My philosophy and training is that as a minimum, to take circles on a cylinder in order to best represent the cylinders direction and use the circles to create a centerline, a minimum is to take two circles, one at the begining and end of each cylinder, but I prefer three and take a third in the middle of a cylidner.

But, would I be better off mesuring those circles and instead of creating a 3D line, constructing a cylinder through those circles instead?

I am i doing overkill by measuring three circles or two cirlces on each cylinder? or is my supplier who is only measuring one circle on each cylinder correct?

thanks

I have attached a picture of a part that I hope can be seen.

the small OD on the left and right sides are dat -A-'s. I measure 3 circles with 6 points, one circle at the begining and end of the cylinder and one in the middle of the cylinder and I do this on both dat -A- cylinders on the left and right sides and then construct center points on those circles and construct a 3D line through those points and use that line as my dat -A-. My supplier takes one circle with 5 points on each cylinder then constructs a 3D line through those two circles and uses that line as dat -A-.

The ID cylinder facing the operator in this view is one of two cylinders, there is one on the opposite side and these cylidners are dat -B-. I do the same with those cylidners, I measure 3 circles on each cylinder and create a 3D line and use that line as my dat -B-.

My supplier is only measuring one of those dat -B- cylinder and using that as dat -B-.

After I contruct my 3D lines, I create a intersction point, axis origin to that point and rotate my axis to lines. In my opinion, I have just set a fairly accurate axis on my part to the datums and I can begin measuring all my features and dimensioning them.

My questions:

My philosophy and training is that as a minimum, to take circles on a cylinder in order to best represent the cylinders direction and use the circles to create a centerline, a minimum is to take two circles, one at the begining and end of each cylinder, but I prefer three and take a third in the middle of a cylidner.

But, would I be better off mesuring those circles and instead of creating a 3D line, constructing a cylinder through those circles instead?

I am i doing overkill by measuring three circles or two cirlces on each cylinder? or is my supplier who is only measuring one circle on each cylinder correct?

thanks

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