What are Gauge Blocks Used for?

Gauge blocks or slip gauges or Jo-blocks are used for calibration, inspection, and verification. They function as standards. According to its grade level, they can be a reference or working standard. Therefore, you could find gauge blocks in the area of the workshop and calibration lab.

The role of gauge blocks is highly vital in various industries especially manufacturing. Manufacturing industries generate high-precision parts. Gauge block is a standard in dimensional quality control. Machinists and woodworkers that work with precision measuring instruments and gauges take advantage of this block gauge to make sure their products accurately meet the tolerance.

Measuring instruments such as micrometer, caliper, and dial indicator are objects to calibrate using this gauge. In this case, you could use the lower grade level of gauge block to use as the working standard on the shop floor. Another tool that works with gauge block is the sine bar. A gauge block is also used to calibrate other lower-grade gauge blocks.

The square gauge blocks are considered more stable. In the event of the gauge block material’s growth or shrinkage occurs at the atomic level, the orientation applies to all of the sides. The amount of change is the same because of the same area. Therefore, you can use it to work with cutting tool positioning, a roller for taper measurement, and a depth gauge. Further, the height gauge (vernier or dial or digital models) makes use of a gauge block for height reference.

When using a gauge block, you should take care of the ambient temperature in your room/workshop. Keep using them at a temperature of 20°C will benefit you get an accurate result.

Gauge Blocks for Outside & Depth Micrometer

A set of gauge blocks for micrometer commonly come with an optical flat as well. The optical flat is very critical to assess the flatness of the flat anvil. The ball anvil micrometer surely doesn’t need this optical flat.

Another type of micrometer that uses gauge blocks for some verification is the depth micrometer. The inside micrometer, in this case, can’t use gauge block to perform any verification. You can use the square block for depth micrometer.

Gauge Block Stacks for Caliper

Wringing gauge block technic can be used to extend its length to achieve a certain desired length. You could do this, especially when facing to calibrate the caliper. Since the caliper’s measuring range is longer, mastering this wringing process is critical. There are four methods to do it.

Wringing the gauge blocks to calibrate a vernier caliper
Wringing the gauge blocks to calibrate a vernier caliper

As you know that calibrating a caliper, either vernier, dial, or digital, is not enough with gauge block. Since they measure internal diameter as well, you need some ring gauges. However, a caliper checker will accomplish those two jobs (calibrating the internal and external jaws)

Gauge Blocks for Dial Indicator

To verify the dial indicator and dial test indicator in the workshop, you could use some gauge blocks. In this case, you need a surface plate or flat base to work with.

Gauge Blocks for Height Gauge

By using the plain jaw and block base, several gauge blocks can be wrung to join and become a precision height reference for the height gauge. You can put in the additional rod to the center hole and apply a screw to keep them stable.

To Work with Sine Bar for Angle Measurement

Sine bar benefits machinists to measure the angle with high precision. The gauge blocks help adjust the angle by adjusting the height of the bar. The three points shape a triangle. By using the trigonometry formula, you will get the angle value. Watch it in the following video.

To Calibrate Other Lower-Grade Gauge Blocks

A gauge block (the master one) is used to calibrate the other lower grade gauge blocks as well. While calibrating the other gauge blocks, there will be using a comparator such as CMM (Coordinate Measuring Machines).

Another way to perform is interferometry. A gauge block can be calibrated using the interferometry technique (interferometer).


It’s not weird that you will find gauge in the workshop (machine and wood shop) and calibration lab. If you plan to buy one set for your workshop, make sure you have understood that they come in several grade levels.

A gauge block can be purchased either as a set or individual. If you have many micrometers or other measuring instruments with different measuring ranges, then the set is recommended to purchase. Some individual gauge blocks are okay to calibrate a single 1-inch micrometer for hobbyists.

So, you have the idea now how important the gauge block is. In many areas in which precision dimensional measurement is required, a gauge block is a vital instrument. Make sure that it must be calibrated regularly. For a more serious job, make sure you calibrate your blocks to the ISO17025 calibration lab. That lab will calculate the uncertainty value of your gauge blocks as well.