# Bolt Pattern Rotation

1. ## Bolt Pattern Rotation

Guys, I need to create a spreadsheet that takes the X and Y coordinates of a bolt pattern, rotates the pattern by an given angle and outputs the new X, Y values. Does anyone know the formula for this task?

Thank you.  Register To Reply

2. ## Re: Bolt Pattern Rotation

You seem to assume that everybody here is familiar with a bolt pattern, what it looks like, which cells it occupies, etc. Otherwise, you would include a sample file or at least a screen shot.  Register To Reply

3. ## Re: Bolt Pattern Rotation

Here is a photo of a similar scenario.

1031_1.gif  Register To Reply

4. ## Re: Bolt Pattern Rotation

Here is the spreadsheet:

Capture2.JPG  Register To Reply

5. ## Re: Bolt Pattern Rotation

I would suggest that, before we get into the Excel programming, we start with some geometry from way back in secondary school.

1) the Unit circle (IMO, one of the very key concepts to understanding these kind of problems) http://www.intmath.com/blog/mathemat...roduction-5166
2) From the unit circle, we get to the concept of "polar coordinates".
x=r*cos(t) -- y=r*sin(t) where r is the radius and t is the angle (in radians, since Excel and almost all other programming languages do trigonometry in radians).

So, for each of your points, you can use basic algebra to get r and t for each point. It should be reasonably obvious, for this case that r is 3.0000. t for hole 1 is 0, t for hole 2 is pi/2, t for hole 3 is pi, t for hole 4 is 3pi/2. (if none of that is obvious, spend some time with the unit circle tutorial).

Displacing/rotating around the center is a simple matter of adding the desired angle (remember that counterclockwise movement is positive and clockwise movement is negative -- again, refer to the unit circle tutorial for this convention) to t, then computing the new x and y for the new points. So, if we rotate CCW through pi/4 radians (45 deg), the new t for hole 1 is x=3*cos(t1+pi/4)=3*cos(0+pi/4), y=3*sin(t1+pi/4)=3*sin(0+pi/4).

If you have any questions about Excel's implementation of the trig functions refer here: https://support.office.com/en-US/art...rs=en-US&ad=US  Register To Reply

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