Measurement

I use bore gauges for most deep hole measurements. I have measured thousands of holes across dozens of shops, and the right tool always depends on the tolerance and the hole depth. Measuring the diameter of a deep hole is not the same as checking a conventional bore. Access is limited. The bore is long and narrow. Standard calipers and bore mikes will not reach past the first 100mm. Over the years, I have settled on five main methods that cover the full range of what I encounter on the shop floor. ...

How In-Process Gauging Works In-process gauging measures the bore diameter immediately after the drill retracts, while the part is still in the machine. The gauge enters the bore at the end of each drilling cycle and takes readings at programmed depths. The two main types I work with are air gauging and contact probing. Air gauging uses a small plug with orifices that measure the gap between the plug and the bore wall. Contact probing uses a mechanical finger that touches the bore surface and sends a signal through the machine’s probe receiver. ...