Precision Measuring Tools - Measuring Up

The deeper you get into racing, the more you will become aware that measuring is a very important part of the overall process. Racers measure everything-lap times, tire pressures, and so on. Basically, racers are going to measure it if it is a mechanical part or process. If you want to improve, you need to measure, and if you merely want to stay the same, you still have to measure.

From a mechanical perspective, measuring is not that difficult. You simply need to make sure that you are using the correct tool to measure. Just as you would not want to measure lap times with only the second hand of your watch, you will not measure pushrod length with a tape measure. You have to pick the correct tool for the job.

When the process involves precision measurement, the list of tools available to the weekly racer is as broad as the price range. We can use micrometers to measure the outside diameter (OD) of shafts and the thickness of shims or sheetmetal. While a micrometer can measure both of these types of parts with great success, we need to understand the level of accuracy required for such a measurement. If we are measuring the OD of a tube used in the construction of a bumper or a frame member, we could utilize a tape measure to measure the cross section of a tube and be quite comfortable with the level of accuracy. However, if you were measuring a bearing journal, a tape measure is not the tool you would use, and even a dial caliper is not appropriate for this type of measurement. You would want to use a micrometer.

The trick when approaching any measurement is to ask the right questions. For example, how critical is this measurement? The answer to that question will drive you to the type of tool you should be using to measure. The only boundary to the tools you can purchase is your budget.

If you are building engines, you need a level of accuracy that will give you exact and precise measurements. If a bearing journal has to be exactly 2 inches in diameter, you will need to use a tool that measures at least to the third decimal place. If your tool only measures to the second decimal, you will be having some real issues. Generally speaking, most quality micrometers will measure to the fourth decimal. This is commonly called measuring to tenths. In reference to tenths of thousands of an inch, or 0.0001, a human hair has a range of diameter from 0.0015 to 0.0021. So when you hear about a dimension or a clearance of 0.0025 for the main bearing to the crankshaft, you have an idea of how close those clearances really operate.

The Saturday night racer may never need to measure to a resolution of the fourth decimal place, but it does not hurt to understand how to accomplish this kind of measurement. In general terms, unless you are building engines and the related accessories (gearboxes and/or rearends), you probably won't need to purchase any ultra-precision measuring tools. For everyday racing and general maintenance, the type of measurement tooling you will require is easy to obtain and the costs are very reasonable.

From a day-to-day perspective, 99 percent of the needs of a Saturday night racer will be covered with a set of 6-inch dial calipers, a 6-inch drop mic with a magnetic base, and a simple dial indicator with some holding brackets and a magnetic base. These tools can be purchased for less than $300 and will last forever with a modicum of care.

If you start to build your own engines, you still may not be required to purchase the complement of tools designed for the engine builder. The reason is that many of the ultra-precision functions will be performed, most likely, by an outside engine machine shop, and it will handle the majority of the precision measurements. The need to double-check what you get will require some tooling on your part.

We can go down the list of tools that a Saturday night racer should consider as minimum requirements and discuss the costs involved. If you purchase brand-name measuring tools from companies such as Starrett, Brown and Sharp, Central Tool, or Mitutoyo, they all have different levels of tools within the same line with costs that can go from very expensive to very reasonable. You can also get tools from some of the import houses, such as Harbor Freight, which offer them at a much lower cost and may not offer as high of a measurement resolution. But you need to ask yourself if you need that level of resolution. If the answer is no, you can spend the difference in money on other parts of your racing program.