The old adage "Measure twice, cut once" exists for a reason. It's hard to put material back after it's gone.
A dial indicator is a simple measuring device that has a plunger that is linked to a dial indicator - when the plunger moves, the dial tell you how far. The accuracy of a typical unit from someplace like Harbor Freight is around .01 inch, aka, down to a hundredth of an inch. You will almost always want to get a magnetic base and adjustable arm assembly to make it easy to mount the dial indicator and set up tests in seconds. It is typically mounted so that the plunger pushes against a part that moves and as the part moves, the dial tells you how far it has moved. Some common uses are to find the run-out of a part such as a brake disc or a machined shaft, measuring end-play in the crankshaft of an engine, or finding TDC as part of degreeing a camshaft. The possibilities are endless, and once you've used one, it's a "why didn't I buy this sooner" situation. At around $40-$50 for a complete setup with a magnetic base - you have no excuse not to own one.
A simple hand-held measuring tool that is used to quickly find the size of a part, it's like a ruler with arms on it and a way to lock the arms in place to see of things are the same size or not. Typically accurate to .1 inch, aka, down to tenths of an inch. Known by various names, comes in various forms, but the basics are the same. Some versions are available with a direct digital readout. Inexpensive and very handy for quick measurements of inside and outside diameters of shafts, lengths of parts, and other details. Not very precise when compared to a micrometer, but accurate enough for many tasks, especially when turning simple parts on a lathe or trying to find out basic information about a part.
A calibrated measuring device used to accurately check sizes down to the thousands of an inch level, aka, .001 inch. Looks like a large C-clamp with a threaded and calibrated screw on one side. Directly measures outside diameters of parts such as crankshaft journals and lengths. When combined with a set of expanding bore gauges, it can also be used to tell the inside diameter of a part such a piston bore. Typically comes in a set where each individual micrometer measures a 1" span. This is the type of tool that is stored away in a secure case until needed - good units are expensive and worth it if you need to do this sort of measuring.
Machinist Starter Kit
A kit that usually includes a protractor, a machinist's square, dial calipers, and some other basic tools. A nice way to get started for very little money. I still use the square and dial calipers from the original starter kit I bought from Harbor Freight.
A simple device to tell you the angle of something. One of my favorite ones is a simple weighted dial (the indicator always points straight up) with a magnetic base. Can be directly attached to driveline parts (such as the transmission output or pinion yoke) to find the angles of each part relative to vertical, and is thus useful for checking the driveshaft angles after doing any major driveline work to be sure all is well.
Page last updated 01/02/2009 01:51:39 PM