‘Depth Gauge’ Guide: Definition, Sizes, and Uses

A depth gauge is a precision measurement tool used by mechanical engineers, manufacturing engineers, and machinists, among others, to correctly measure the depth of a bored cavity, recess, hole, groove, or other similar apertures made below the surface level of a material. The material’s surface serves as the reference plane against which the device measures depth.

It should be noted that the word depth gauge can also refer to a variety of other goods. One option is to utilise a pressure monitor and display to indicate the pressure level associated with a certain depth of immersion in water. This type of device, sometimes known as a diving depth gauge, is used by scuba divers to measure the pressure associated with their dive levels. Another application of the term depth gauge is in medical applications, referred to as a surgical or orthopaedic depth gauge. This tool is typically used to determine the depth of holes bored into bones for anchoring implants or other similar surgical uses. The remainder of this article will concentrate solely on the first sort of depth gauge, namely the device used in machining metrology.

Groz 300 mm Digital Depth Gauge DDG/12

Types of Depth Gauge
There are various types of depth gauges available in the machining metrology space. The primary types are as follows:

    1. Depth gauge with an analogue dial
    2. Depth gauge that is digital
    3. Micrometres for measuring the depth
    4. Depth rulers
    5. Vernier depth gauge

Let’s get a better understanding of the different types of depth gauges:

1. Analog depth gauges: They have a mechanical dial and a needle indicator to show the depth measurement on the dial face.

2. Digital depth gauges: They are also known as electronic depth gauges. In this type, the dial and needle indicator used in dial depth gauges is substituted with a digital display that directly points at the measured depth with numbers. Because these devices use an electronic display, a power source – often a battery – is required to power them.

3. Depth gauge micrometres: They have a rachet that can be twisted to move the spindle face into the recessed opening until it comes in contact the bottom of the hole. The depth gauge micrometre’s thimble and sleeve are equivalent to those found on a standard micrometre, and reading the depth value is performed in the same method.

4. Depth rulers: These are also known as rule depth gauges. They are a simpler depth gauge type with a graded straight scale or ruler attached to a locking bolt that may be moved up and down into the recess to acquire a depth reading. Some depth ruler models allow the user to adjust the orientation of the scale relative to the plane of the base surface, allowing it to be used to measure both the depth and the angular location of the aperture. Depth rulers often have poorer resolution than other forms of depth gauges.

Yuzuki 150 mm Vernier Depth Gauge

5. Vernier depth gauge: This type employs the same vernier scale principle as a vernier calibre. The vernier scale allows the user to increase the precision of depth readings by mechanically interpolating off the scale against the main scale. Vernier scales enable exact measurements without the need for additional graduation marks on the primary scale, which eventually renders the instrument unreadable.

Next, let’s talk about the sizes/dimensions and other specs:

Dimensions and Specifications of Depth Gauge
There are several crucial parameters and features to consider when choosing a depth gauge before settling on a specific type or model. The following are typical parameters; however, some may differ based on the specific type of gauges being evaluated:

• Base length: The size of the base, which is the section of the gauge that stays above the recess and serves as the measurement’s reference plane.

• Measuring rod count: Certain versions include numerous replaceable rods, allowing the instrument to be used to measure a wider variety of recess depths. Do check that the rod selection for models with available rods that can be changed is consistent with the projected depth being measured.

• Measuring rod diameter: This indicates the size of the measuring rod, which must fit into the recess to acquire the measurement. The width and thickness of the scale are equal measurements for depth rulers and other forms of depth gauges that use a graded rule or scale.

• Maximum measurement depth: This shows the greatest depth that the depth gauge can measure. This value may vary greatly depending on the rod used in gauges with interchangeable rods.

• Resolution: It is also known as graduation. It refers to the magnitude of the incremental depth number that may be read off the gauge’s scale. The resolution will vary depending on the gauge used, with depth rulers having lower scale resolutions than digital depth gauges or depth gauge micrometres. The resolution of a digital tool is determined by the number of digits displayed and the least significant digit visible.

• Dial range: The dial range indicates the two extreme depth values presented on the dial for dial-type depth gauges. Digital depth gauges may provide a measurement range, but the range can be deduced from the number of digits in the display field.

• Measurement scale: Depth gauge measurements are typically given in inches or metric (millimetres), with some versions having both scale options.

The size of a depth gauge is typically specified as the dial range across which depth measurements are displayed or the maximum allowable depth as defined above.

Insize 300 mm Digital Depth Gauge 2141-202A

Depth Gauge Applications
The depth gauges described in this article are primarily used to make exact measurements of depth dimensions in machining and production applications.

Other than in machining metrology, depth gauges are used in medical applications as surgical instruments (surgical or orthopaedic depth gauge) and to measure the depth of divers (diving depth gauge). Lower accuracy depth gauges are also used, for example, to measure the remaining tread on vehicle tyres (tyre tread depth gauge) or to examine the depth of threads cut on threaded fasteners (thread depth gauge). Other instruments with similar names are used for specialised applications such as raker, top plate angle, and cutter length maintenance on chain saws. Finally, some water level gauges used to monitor sea level depth during various tide cycles are also known as depth gauges.

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