radius

You need to supply more information. In particular, what is the shape you are dealing with and the degree of accuracy and precision. There are many ways to estimate the radius of a curve, and many different type of tools to obtain differing degrees of accuracy and precision. Some methods include measuring two tangents to a curve and the angle betwen the tangents, measuring the distance from an outside perpendicular to the apex of two tangents to the ends of the curves and the angle, measuring the distance of two perpendiculars inside the cuve between the curve and the point where they intercept.

if its small piece use radius gages;

if it is really camber or deviation from straightness that you are after, on a bar or rod you would place the material on two rolling supports, determine TIR, total indicator readout, and then solve for the pythagorean theorem for the two right triangles from th indicator and to each roller.

Hr = length from "center" to therollers

h equals one half the tir (ie from theoreticalcstraight to the maximum TIR condition)(tir=2H)

r-h equals the long side of the triangle

c= 1/2 the distance between the two supports.(L/2)

r-h=sqrroot of r^2 minus c^2 (pythagorean theorem)

milo

Good Answer.

It's the same technique used to determine the radius of a curved piece of railway line using a tape measure and a piece of string.

• Take three points equidistant along the curve.
• Strike a chord between the two outer points.
• Measure the distance between the centre of the chord and the apex of the curve. Call this the versine.
• Versine = Radius x (1-cosine(half-angle)). Now while absolutely correct, the formula isn't very useful in this form, so with a bit of algebra it becomes:
• Versine = Radius² ÷ (8 x chord length) as a very close approximation.

This is a method of two inside perpendiculars. It works well in situations where you have the room to measure from the inside of the curve. There are other methods using the tangents on the outside of the curve also. You can also measure the distance between the midpoint of the inside stringline and the curve, and calculate the radius of curvature.

Thank you all.

It is a small piece 30" long x 12" and I needed to copy the 'depth of the curve.

This will work for me.

Thank you again.

Smitty