Placing Holes On a Pitch Circle Diameter (PCD) 7

Harold Hall


General notes

Where a large number of rows are concerned the formula in row one can be cut and pasted into subsequent rows making the process very fast even if say two hundred rows are required. In this case add one line at a time to make say ten lines and then cut and past the ten lines adding ten at a time.


The formula uses the cell references, ie, D11 in the above formula relates to the angle between holes.


2*PI in the above is necessary as the spread sheet works in radians rather than degrees.


A major advantage over using a calculator is that a printout of the results can be made that can be taken to the workshop for use.


An interesting example

Elsewhere on the site I show a barrel shaped conrod being made for which I used a spread sheet to calculate the coordinates along its length. Subsequently, I was making a dining table for which I chose to make the sides and ends very slightly curved. My usual method for cabinet making is to use a suitable length of string with a pencil to mark out the curve to be worked to.


Attempting the idea I soon found out that the string needed to be very long and calculating this it worked out to about 20metres, the only place large enough to do this was in the road outside, obviously not practical. I then remembered the spread sheet that I had developed for the con rod.


With the program open I entered just the number of stages and the depth of the curve and immediately the values were displayed. I then took this to the workshop and made a template, just for one edge. However, I decided that the result was not sufficiently curved and returned to the spread sheet again entered the number of stages and a greater depth to the curve and again the results were immediate. Obviously, the process saved a considerable amount of individual calculations which resulted in a few hours saving in time. The result therefore shows that a sheet that was set up for something about 100mm long also found use with one around 2M long.


Spread Sheets are definitely worth attempting!


Workshop Processes