Dave,
A micrometer is a very useful tool to use in aircraft sheet metal construction. For maximum hole quality, you can quickly measure the diameter of any fastener and armed with that information, drill the hole to optimum size. A micrometer and drill index chart practically go hand in hand. Example: Most blind fasteners are not as strong as solid rivets and can benefit from optimum hole quality. Many builders simply drill a #30 hole for use with blind fasteners. If you used a micrometer to measure the diameter of many of the blind fasteners Van's ships with its kits, you will quickly discover many types measure out at .125 so by referring to a drill index chart will see a 1/8" drill bit is the better choice and will produce a snugger, tighter fit in sheet metal.
You can use a micrometer to measure the diameter of individual bolts and can then confidently drill and ream its hole knowing it will be the correct size. If you are really a stickler for precison, you can measure that hole you just drilled with a ball gauge and the micrometer will tell you for sure if it is the correct size or not.
With a micrometer, you can quickly determine the thickness of any skin or sheet metal part or stack up of sheet metal parts. This can be helpful when fabricating a shim or doing a repair. I'd wager most people would have difficulty eyeballing the difference between .025 and .032 sheet or .032 and 040 aluminum sheet. Why guess? Use a micrometer.
You have a drill bit or reamer in your hand but the identifying marks on it are obscured or worn away and you don't know for sure what size it is.....use a micrometer!
Somebody walks into your shop with a well used screw or bolt in hand and asks "What size is this?" With a micrometer, you can quickly determine the answer in seconds.
I recommend you purchase and routinely use a digital 1" micrometer. You will not be dissapointed and its utility and ease of use will go a long way towards helping you build even higher quality into your project.
