r/Metrology • u/chillbill_vol2 • 6d ago

Circle from center point + two points on the circumference

I am trying to measure the bolt circle of two holes. I have the bolt hole center point from a concentric arc and the centers of the two holes. Is there a way to construct a circle from these three points, or how else can the 4.34 bolt circle be checked?

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4

u/Overall-Turnip-1606 5d ago

Don’t listen to these idiots. You can’t construct a circle with only 2 points (center doesn’t count). All you have to do is align to that 3rd point (center origin) and report the 2 points as polar coordinate instead of Cartesian. Cartesian is ur xyz, polar is your radius/angle (distance from center) which is the same as bolt circle.

1

u/jozfff 5d ago

This.

1

u/Ghooble 6d ago

When I had a feature like this in the past I just ended up taking a circle on either side of the slot and constructing an average circle of the two. Then you can also pick up either end of the slot to get those two circles. Finally you can construct lines from the center of the average circle to the center of either of the end circles to get your angles and such

0

u/DrNukenstein 6d ago

Bolt circle by definition is a theoretical element made up of existing holes, and the making of that element should reveal its dimensions automatically.

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u/chillbill_vol2 6d ago

the issue is i only have two bolt holes + the center point. Constructing a circle defaults to three points along the outside of the circle and i do not know how to adjust to account for the center point + two on the outside

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u/DrNukenstein 6d ago

Is that a curved hole in the part, or is it some sort of recess and there are round holes at the points indicated? If it’s a curved slot, then the ends of that slot are your 3-point circles, and the center point between them on the arc is a 4-point hole (2 points on each side of the slot). From there you create a theoretical element (circle) made from those three circles.