Reflect on the Importance of Precision Measuring Tools

When building an AR-15 Rifle it is important your barrel is at least 16 inches in length to meet the requirement. This is when using a tape measurer or ruler may be used for the measurement. However, something that long you would not use calipers or micrometers for because these tools are meant to be used on things much smaller. For example, when drifting sights on and off of a handgun you will need to be sure the new sight sits center on the slide to ensure an accurate shot after install. A caliper can be used to measure the difference from both sides using its depth rod and you would split the difference until the sight reads the same measurement on both sides. Using the SDI Gunsmithing Tools Lab book issued during the course it says that the “dial indicator is used to measure ‘travel’ or play”. They are referring to the tools ability to measure both high and low spots on an item or more specifically when they say play this may refer to the amount of give or movement a machine will read while using this tool to check your mills and or lathes. Another use for the dial indicator is measuring “runout” or the wobble of an item. If using your lathe to machine threads on a barrel it would be important you know the barrels "runout" at the muzzle you plan to thread.