Maybe you’re thinking “Who cares about the shaft diameter on bindery equipment, just look it up in the manual if you need the info!” We can say that as a supplier of bindery products to fit hundreds of machines with all kinds of shafts, there is often a noticeable lack of information available. At the very least there is often some measure of confusion about actual dimensions, especially if no caliper is available to take a precise measurement.
So if you find yourself ordering some accessory or kit to fit your bindery equipment, here’s a quick video tip to double check that your information is indeed correct.
The essence of the tip involves a bit of simple elementary school geometry you swore you’d never need. We’ll describe it here, and the video illustrates how simple it is. The formula is Circumference ÷ Pi = Diameter.
To easily find the circumference, take a strip of paper and wrap it around the shaft in question. Where the strip overlaps itself, make a mark. Now take the measurement from the end of the strip to the mark and you have your approximate circumference. This isn’t exact but it doesn’t have to be. We’ll see why shortly.
In this video example, we end up with about 95mm ÷ 3.142 (Pi to 3 digits) = 30.2mm. Round to the nearest whole number and we end up with a shaft diameter of 30mm. Why do we round?
In the case of folding machines and other bindery equipment, we know metric shafts are typically 15, 20, 25, 30, 35mm, etc., and standard shafts might be in inches, .875, 1.0, 1.125, 1.25”, etc. Manufacturers typically stick with customary increments in their design and use of shafts.
If our circumference measurement were perfectly accurate, of course we’d end up with a perfect result. But remember we don’t have the tools we need to start with, and with manufacturing conventions used in our industry, this approximation will get us close enough to confirm the diameter. That way we are sure to order the right components to fit our machines.
Who says we don’t need geometry!