A Note to Newbies
When taking a measurement, close the jaws only lightly, with consistent pressure from one reading to the next to obtain accuracy. Try experimenting by pressing a bit harder and you'll see that it's possible to change the reading. This isnít the material moving but the calipers are actually flexing. So donít press too hard. With practice you should get the feel of what is proper. Practice for a while on a gage block or some other solid object until you get repeated readings.
For general measuring use the flat area of the jaws whenever possible. The ends of the jaws are beveled to get down into slots and grooves however using this beveled area more than necessary will wear the jaws down quickly. As they wear your accuracy will decrease proportionately. You can see any wear by putting the jaws together and holding them up against the light.
Youíve heard the saying ďuse the right tool for the right jobĒ, well this is true for calipers too. The most common calipers have a measuring range from zero to six inches. These are the most useful because they can be handled easily. But know that it is difficult to take readings near the end of the range of these calipers without compromising accuracy. There are larger 8-inch and 12-inch (and even longer) available that might be more suitable. But donít think to be clever and own just one larger caliper to cover all the basis because youíll discover that the longer the caliper the more awkward they are in making small measurements. And speaking of using the right tool, use a caliper for what it is intended for. Itís not a screwdriver or a pry bar!
Brand new dial calipers may exhibit some roughness in movement. What you are probably feeling are the gear teeth traveling along the rack. This is normal but after some time, with use, they will smooth out somewhat. Wipe the beam before each use if you are working in a dirty environment to minimize getting dirt and chips into the rack teeth. Donít oil them because that would only act as an adherent for dirt particles. Use air to blow away chips and grinding dust.
After a measurement itís best to keep a caliper, or any other precision instrument for that matter, in the case that it came in. Laying it around the work area without any protection just increases the chance of something bad happening to it. Stay organized.