Whatever the reason, it’s important to realize when you need a precision measurement. In these cases, a steel rule or a tape measure simply won’t cut it. Using one of these when you need a caliper would be like using an adjustable wrench instead of a torque wrench and hoping you’re torqued to spec. In general, a steel rule will be precise to roughly 1/16″ (.060″). While the laser markings on the ruler itself are higher precision, the human eye is really the weak link in this equation. A tape measure is even less accurate due to the fact that it is not rigid and must also be interpreted by the human eye.
Conversely, a digital caliper is significantly more precise and does not rely on human interpretation to assess the measurement. A digital caliper is generally precise to .001″ or better (if you need even higher precision you will need to find a good micrometer). So long as you use it properly, a digital caliper will provide a readout of the measurement you take and you won’t need to trust your eyes.
When using a caliper, there are a few steps you should be aware of to ensure accuracy. First, you’ll want to make sure the jaws are clean and free from any debris such as oil film or dirt. The presence of either of these can skew your results by a few thousandths of an inch. Additionally, when you store your caliper, you’ll want to make sure you store it with the jaws not touching, as this can introduce minor stresses into the system and increase wear on some of the measurement components which can throw your tool out of calibration.
The Best Digital Caliper
Calibrated precision measurement equipment is one place where you most certainly get what you pay for and as such it pays not to cheap out. The digital caliper we always recommend and have used for years is the Mitutoyo AOS Absolute Scale Digital Caliper. Mitutoyo is a company that has a longstanding history of making extremely high quality precision measurement tools and other calibrated equipment that is found in machine shops, assembly lines, and R&D labs across the world.
When it comes to their AOS Absolute Scale Digital Caliper, the 6″ version is long enough for most automotive tasks and should be perfect unless you have a very specific project that requires an 8″ caliper (which you can see by clicking here). The Mitutoyo AOS measures in .0005″ increments, and shows your measurement on the LCD screen. With the click of a button, you can easily switch between metric and SAE units, as well as zero out (tare) the caliper. The AOS (which stands for advanced onsite sensor) is enclosed in a dirt, oil, and water resistant housing that makes this tool extremely long lasting.
As far as measurement capabilities, there are two sets of jaws. The first set of jaws lets you measure outside dimensions (such as the outer diameter of a hose) and the second set is designed to let you measure inside dimensions (such as the inside diameter of a hose). There is also a probe on the end that makes it easy to measure depth. The caliper comes with a nice molded case to protect the tool when not in use and is battery powered with a replaceable battery.
Overall, Mitutoyo makes on the of the best digital calipers around (but we’ll give Starrett an honorable mention too since they also make awesome digital calipers) and we think you’ll be extremely happy with your decision to get one. As far as where to buy, we suggest Amazon as their price seems to be one of the lowest around. While the Mitutoyo is our favorite and the one we have used for years, there are other quality calipers out there as well so if this one doesn’t quite fit your needs, feel free to have a look at other calipers available by clicking here. Happy wrenching!