Wow, alot of misinformation here.
First off, the federal specifications for a retractable tape measure are +/- 1/32 inch for the first twelve feet, +/- 1/16 inch above that. Most companies will exceed this tolerance, but you have to call because they vary from tape to tape.
The federal spec for a long line steel tape (type you have to roll up) is +/- 0.100 inch/100 ft with a specific amount of tension applied depending on the length.
Yes the hook moves the thickness of its tab to account for inside measurements.
Comparing two tape measures by lining them up side by side is not the correct way to calibrate a tape measure. You either need an optical comparator (and alot of free time), a cmm, or a laser interferometer.
Starrett tape measures are terrible imo. Its not because they are usually out of tolerance, it is because the lock and the reel are poor designs. The locks either fail and won't hold the tape, or the reel is so tight near the end that you have to force it out. I am in no way saying their products are bad, I am just saying they should start making them domestically again.
The Lufkins and Stanley tapes are much better. The Lufkins have the best locking mechanisms and almost always exceed their own tolerances by a substantial amount. The Stanleys are the most durable, ever see the commercials with the hammer hitting their product over and over again, thats them. The coating on the Stanley tapes seem thicker, how long that prevents rust, I'm not sure.
Chinese tapes, stay far, far away. The metal is often cheap, not treated correctly and the hook is a soft metal and often bends easily. This means that years later your tape is rusted and has either shrunk/grown due to the metal not being aged enough. The hook has bent out and the rivets are coming out. What are the Chinese tapes accurate to, does China have a standards bureau to conform to?
Your not going to get much better than than 0.030 inch on a tape. Starrett, Lufkin and Stanley are all similar in accuracy, each specs their tapes differently though. If you need something more accurate, steel rules are as accurate as +/- 0.0025 inch for a Starrett (would recommend). Get a caliper for even more accuracy (+/- 0.001 inch).
Last edited by cheese9988; 03-05-2012 at 10:37 AM.