How Precise Can You Be With Ordinary Tools?

I recently prepared a ScopeRoller order for a customer in Spain.  The sleeve part of the product I make by cutting sections off a 2" O.D. aluminum tube using a chop saw.  I use a stop to hold the tube in position for cutting each piece, and because one end is a 30 degree angle, and the other is a right angle, I do a slice at the 30 degree angle, then move the blade to the 90 degree angle to cut the next section.  (You may recall from geometry class a theorem appropriate to proving that these will end up consistent from one section to the next.)

Before putting this order together, I decided to measure how precisely each of these sleeves matched in length.  Unless the sleeves are more than a tenth of an inch difference, few customers would ever notice.  The design means that even rather larger differences would make no functional difference.  To my pleasure, the three sleeves that I had lying on the workbench were within 0.010" in length!