Depth Micrometers: Everything You Need to Know

Depth micrometers are standard tools used to measure the Depth of slots, keyways, grooves, and other locations. They provide very accurate measurements.

People often use depth micrometers to take very accurate measurements. Measurements in inches can be taken down to .001″ or .0001″, while millimeter measurements can be down to .01mm or .001mm.

How To Use a Depth Micrometer

To use your micrometer:

  1. Ensure the measuring tool and the area you want to measure are both clean. The thimble for a micrometer should turn quickly.
  2. Put the tool over the hole on the part.
  3. Spin the micrometer thimble until the rod reaches the hole’s bottom.
  4. If your tool has a ratchet or a friction stop, use it.
  5. When a rod is changed to measure a different size, the depth mic should be checked to ensure it is still accurate. Between the micrometer and the depth rod, where they meet, it’s easy for something to get dirty.

How To Read a Depth Micrometer

A digital depth micrometer is easier to use than an analog one, especially if you will not use it often. However, digital depth micrometers can be pretty expensive. If you need to use an analog one, continue reading.

Depth micrometers are standard tools that measure small distances. There are two types of depth micrometers– one reads in increments of .001 inches, and the other reads in increments of .0001 inches. Both types work similarly- there will be graduations on the sleeve of the depth micrometer, similar to markings on a ruler.

The graduations marked every fourth interval are numbered 0, 1, 2, and so on. These figures represent.100 “a hundred-thousandth of an inch. The graduation marked six corresponds to a measurement of 1.600″ if you use a depth micrometer with a 1-2” rod. Each gradation between the digits is.025 “or 25 thousandths of an inch.

Depth micrometers measure the distance from the bottom of an object to the top of the thing. If we used a depth micrometer with a 4–5-inch rod and took a reading at the third graduation after the.200-inch mark, we would get 4.275 inches. If the 0 on the thimble lines up with the 3rd gradation after.200 on the reading line, this is our measurement.

If the number 10 was lined up with the reading line, and we could still see the third graduation after the.200′′ mark, then our measurement would be 4.285′′. For micrometers that can measure up to.0001′′, we turned the micrometer without turning the spindle to see which numbers on the sleeve and thimble lined up. If the number on the thimble lines up with the number 7 on the sleeve, the new reading is 4.2857′′.

The formula for Depth Micrometer Readings

The size of the micrometer rod is the base depth plus (.100″ times the most significant visible number) plus (.025″ times the graduations visible after the largest number) plus (.001″ times the reading from thimble) plus (.0001″ times the reading from sleeve for .0001″ micrometers).

Example for a depth micrometer with a 1-2″ rod

1.000″ + (.100″ x 4) + (.025″ x 2) + (.001″ x 3) + (.0001″ x 8) =

1.000″+ .400″ + .050″ + .003″ + .0008″ = 1.4538″

When To Use a Depth Micrometer

Depth micrometers are very accurate, but they have one downside. Depth micrometers are most commonly found in 1″ measuring range increments. It means that multiple-sized rods are needed to be able to cover the measurer’s measurement needs. Because of this, depth micrometers are commonly sold in sets.

If you want a set of micrometers, a 0-3′′ group should work for most purposes. If you need a micrometer set that is longer than 3″, then you should get a 0-12″ set.

What Makes a Good Depth Micrometer

Depth micrometers need two things to work well: precision and accuracy. You can adjust most depth micrometers to make up for small inaccuracies, but nothing can fix a tool that isn’t precise.

A suitable quality depth micrometer will turn smoothly without any drag. It is a sign of a good tool. If your depth micrometer ever feels like it is rubbing internally, disassemble the micrometer. Clean it as the manufacturer directs to eliminate any dirt causing the problem.

Where To Buy Depth Micrometers

Depth micrometers can be bought from some online stores. If you want to know more about depth micrometers and which is best for your needs, please read our reviews section.

Are Cheaper Depth Micrometers As Good as Expensive Ones?

Some cheaper depth micrometers are made in China. They have gotten better than they used to be, but they are not as good as those from Starrett or Mitutoyo.

Depth micrometers are a type of tool that you will only need to buy once. In most cases, searching for a used depth micrometer on Craigslist, Facebook marketplace, or eBay is better.

How To Calibrate a 0–1″ Depth Micrometer

  1. Verify that the micrometer is clean.
  2. Visually examine the micrometer for any condition that could cause errors in the calibration.
  3. If you need to adjust the tool, be careful and clean it so that no damage is done to the internal threads.
  4. Spin the thimble until the depth rod is inside the tool.
  5. Extend the depth rod to the zero position by spinning the thimble on the tool. If you have a ratchet or friction stop, use it to keep the depth rod in place.
  6. Repeat the procedure by putting the depth micrometer on gage blocks and hanging the tool while allowing the depth rod to extend down to the surface plate.
  7. Check the accuracy of the micrometer at different locations on the tool. Use gage blocks that have been calibrated themselves to do this. Test the micrometer to varying positions on the thimble, not just at increments of .025″, to ensure the scale on the thimble is accurate.
  8. At this stage, any necessary adjustments may be made. The method of adjustment for each depth micrometer is different. If required, consult the manufacturer’s instructions to learn how to adjust your depth micrometer properly. If changes are needed, the calibration process should be restarted; otherwise,
  9. Calibration results are usually recorded in a register or database so the measurement history can be traced.

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Frequently Asked Questions About Depth Micrometers

Is Depth Gauge a Part of Micrometer?

Engineers use the depth gauge micrometer, a precise measuring tool, to figure out how profound something is. When you turn the rachet, the face of the spindle moves 0.5mm closer to the bottom of the blind hole. The picture below shows how to use the depth gauge.

What Is Unusual About a Depth Micrometer?

Depth micrometers are tools used to measure the Depth of small holes and bores. They are very sensitive, so they need to be handled with care. Engineers and mechanics use these devices to get precise measurements. Reading depth micrometers is a delicate process that must be done correctly to get accurate results.

What Is a Depth Micrometer Used For?

Depth micrometers measure the Depth of holes, slots, shoulders, and other projections. They work by using a high-precision ratchet thimble to measure on a vernier scale. Different measuring rods with varying depth ranges can be used with these micrometers.

What Are Advantages of Depth Micrometer?

Depth Gauge has an accuracy of 0.01 mm, which is suitable for linear measurements. It is also more accurate than vernier calipers. If you want to make observations easier, choose a Digital Depth Micrometer. Both types of Depth Micrometers have the same level of accuracy.

How Do You Read Depth Micrometers?

When reading a depth micrometer or inside a caliper-type micrometer, the number shown on the major scale is the first number hidden by the thimble. In this example, 0.4 inches is the first number hidden by the thimble. The thimble scale aligns with the index line at 0.020 inches.