Using Dial Indicators

Dial indicators are designed for used on a wide range of standard measuring devices such as bench comparators, indicator plug gages, depth-indicating gages, indicator snap gages, bore indicator gages, and thread-indicating gages.In an other words , dial indicators are precision measuring tools with a myriad of applications in the machine shop. Once you move beyond the basic machining operations you will definitely want to have one or more of these in your workshop. Here we will describe the instruments and holders.

A plunger moves in and out from the body of the indicator and rotates the measuring needle on a dial face. Dial indicators usually have either a 1" or 2" range and are calibrated in increments of .001". A smaller dial reads each revolution of the larger dial in increments of 0.100".
The outer bezel rotates and turns the numeric scale with it so that you can set the indicator to zero at any plunger position. Most D/Is have two little movable markers on the outside of the dial face that can be used as reference points. I have removed them from mine, since I rarely use them.
Here are some things you can use a dial indicator for:
�?Centering cylindrical stock in a 4-jaw chuck
�?Determining accuracy of lathe or mill alignment
�?Determining runout of lathe spindle and chucks
�?Aligning stock for milling
�?Monitoring depth of drilled holes
�?Monitoring vertical movement of milling head
�?Determining if edges of a rectangular workpiece are parallel
This is far from a complete list. Once you gain familiarity with this tool you will think of many ways to use it.
Here's a photo of a dial indicator (DI) set up to center a bolt in a 4-jaw chuck. If the bolt is off-center, the DI plunger will move in and out as the chuck rotates. When the bolt is properly centered there will be little or no movement of the plunger and the needle of the DI will move only .001 or less.