If there's some other example you'd like to review, let me know. If you were measuring the angle of the lip on the D1 spindle, it seems you got it right. The edge of the lip is not very wide so that's probably how much the needle deflected downward or upward when you moved the DI 0.2" horizontally. Therefore the rise (or drop depending on which way you were moving) was 0.025 and run was 0.200". Arctan (0.025/0.200) = 7.125*. That by the way, is the one-side angle. The included angle (the angle from the centerline) is 14.25* which takes into account both angles.
Now, lets turn it around... What happens if you only know the one-side angle and someone tells you it's 7.125*. What would be the rise over run?
EDIT: In the original post here, I mis-wrote something. What follows has been edited/corrected as not to cause anyone confusion. -ray
With a calculator, calculate Tangent (7.125). It equals: 0.125. Now, you just find any two numbers whose quotient equals 0.125. That is A / B = 0.125. Pick a number, any number... Let's say 3. Now substitute 3 for either A or B; I'll use A.
3 / B = 0.125". or, B = 3 x 0.125 which equals: 0.375. This means that if you move in 3" in the horizontal direction, the DI needle should deflect 0.375".
The trick of course, is to pick the first number in a range corresponding to the distances you're working with.
Does that help?
Ray
So, no less confused. It seems as if some are saying I want tan and some arctan. I might need both. What I am hoping to accomplish is to learn how Ray C ran the calculations. I'm dreaming I can learn the formula and not need to use charts. I prefer to be able to scratch math out with pencil and paper. I then leave myself the process and examples in my notes. I can refer to these and remember how to figure things such as how to set up my rotary table for dividing. If I can get this process down, I can use it to do different angle set ups. I learn best through interaction and was hoping someone could lead me through this in terms vastly more simple than proper technical math terms. Explaining the proper terms so a simpleton( ie me) gets it would be great too. " the spindle DI gave me 0.025" the carriage moved 0.200". Arctan (0.025/0.200) = 7.125*." This shows the Problem as Ray layed it out.