...but I don't feel like thinking.

An oval slot could be described as two circles a certain distance from one another. If the center of the slot, lenghtwise, is say, 100 mm from some feature, given the length and width of the slot, is there a simple formula to find the locations of the two circles along the same axis?

Generally a slot is not an oval but two parallel lines that typically terminate in half circles of diameters equal to the width of the slot to determine the distance between the center points.

If this is what you are looking at then you would just take the width of the slot - that is the diameter of your circle and then subtract that measurement from the overall length of the slot.

If it is truly an oval then your calculation is a bit more tricky. An oval has two arcs of equal measure on each end and two arcs of equal measure on the long side.

Are you saying that you have the length and width of the slot?

If you have the kind of slot that Ami first describes, not an oval, and you have the length and width of the slot, the center of each circle will be one-half of the width from the each end of the line.

C1 - Circle one
C2 - Circle two
A = one end of slot
B = the other end of slot
L = length of slot
W = Width
M = Middle point of slot (Middle point of line AB)
D = center C1
E = Center C2
Line AB is the length of the slot

You want the location of D and E. You find that by subtracting the radius of the circle from the length of the slot. That distance from each endpoint is the center of each circle.

W/2 = Radius of C1 = R

D = AM - R
E = BM - R

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I think that is it. I think Ami's method forgot that the center of each circle will be a distance equal to the radius away from each end.Try drawing it and labeling each point as I have given. I think you will see it then.

Are you sure DG?

Wouldn't it be:

D = (M-0.5L)+R
E = (M+0.5L)-R

If my slot dims are

L = 10
W = 6
R = 3

and M lies at 100, (in my coordinate system. Er, did I forget to mention that?)

D would be at 98 and E at 102.

Correct?

I didn't realize that you were usubg coordinates. But that really shouldn't make any difference, I think.

In plain English, the center of each circle will be on a straight line extended from one radius of one circle to a corresponding radius of the other circle. The entire radius of each circle is on that line (That is, you are not connecting a point on one radius to a point on the other). Since you gave the length of the slot (that should be equal to the length of the line I just mentioned), the center of each circle will be on that line at a distance of one half of the width of the slot away from the end point of the line. That was what I attempted to indicate by my first post. I realize that it may have been wrong or not clear.

In any case, the middle of the line being 100mm from something isn't necessary to find the center of each circle, and the diameter isn't necessary either, except for the fact that it is equal to the width of the slot. But, since you want the center of each circle, the length of the radius is the important value. Being given the length and width of the slot (and that the slot is like Ami first described, two halfcircles and two straight lines) gives you all the information needed to find the centers' location.

Thanks guys. Yeah, the slot is of the parallel sided type. I used the term 'oval' to differentiate between this slot and a rectangular type, i.e. one with no radii.