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View Full Version : Simple Fun With a Four Fold Rule



Jim Koepke
02-08-2011, 7:25 AM
Having trouble sleeping, so I thought I would share this.

I have been using my wooden four fold rulers more of late. The hinges actually seem to be useful as natural dividing points.

While in the shop making a stool for my wife the stock for the legs was being worked. It was to be cut into four pieces. For the first cut in half, I usually measure and divide the length and make a mark in the middle. This time it was also measured and marked from the other end. Finally the cut line was drawn between the two lines. This takes care of those pesky sixteenths and thirty second measurements.

When there were two pieces, an idea came to me. The two pieces were lined up side by side and flushed up at the ends. Then with a four fold yard stick the center was marked by laying the four fold on the pieces and letting the end hang over the stock an equal amount at either end. A pencil mark was made at the center hinge across both pieces. Then one piece was flipped end for end and my knife line was scribed between the pencil lines. They were less than 1/8" between them and it was just marked by eye.

In this case, all four legs turned out to be less than 1/32" difference between them. What is really strange is this is better than any of my results with careful measuring and I couldn't tell you how long these legs are other than they are maybe longer than 16" and less than 17".

In my experience the more the measurements are thought about, the more likely a mistake is going to occur.

jtk

Jonathan McCullough
02-08-2011, 8:13 AM
If it's what I think you've done, it is an old draughtsman's trick of the trade. I was shown how to divide the space between two parallel lines into as many equal pieces as necessary by finding a multiple number and laying the ruler diagonally across the two lines, then marking off the multiples. If your parallel lines are square with respect to your drafting machine you could just mark them off, but if they weren't you could just do what you did and flip the ruler over to mark off the multiples in a diagonal going in the other direction, then lining up the dots with the ruler and drawing your line(s). Pretty cool trick.

Jim Koepke
02-08-2011, 8:25 AM
That is a cool trick that I have used in the past.

This one was just having each end of the ruler hang over the end of the stock by an equal amount. Then the center hinge was at the center of the stock.

This ruler is marked in 1/8" increments, so lining it up was faster than trying to make accurate calculations and then measurements.

jtk

Jim Koepke
02-10-2011, 5:20 PM
Here is a picture to make this clearer:

182165

The center is at the hinge.

jtk