Accuracy is challenging in every field. In physics, accuracy and efficiency depend on one of the parameters known as measurement. We are familiar with using scales, compasses, measuring tapes, clocks, thermometers, and many more.
Each device is used to measure different parameters. A screw gauge is a mechanical tool used to measure the diameter, radius, or thickness of a wire or metal sheet. We have also studied vernier caliper scales and micrometer gauges in our previous sessions.
In this article, let us know about a measuring device known as a gauge and the types of gauges.
What is a Gauge?
A gauge is an important measuring device in the field of design engineering. It is a device used to provide certain dimensional information, according to a specified standard or system.
Some gauges are meant to measure the size of the object. But, most gauges are mainly used to specify if the dimensions of the measuring object are less or greater than defined standards that are within the tolerance range. Gauges can be operated electrically or mechanically.
They are generally considered as fixed-type or deviation-type instruments. Fixed-type gauges are designed to showcase if a given dimension is larger or smaller than the standard. They are usually made of soft steel, hard steel, or glass.
To prevent rust, fixed-type gauges are chrome-plated or tungsten-carbide-coated. Now, let us know more about the various types of gauges.
Types of Gauges
Gauges are used to measure different types of objects having various sizes, shapes, and thicknesses, the gap in space, the diameter of materials, or the pressure of the flow. Specific types of gauges are used to measure each parameter.
The following are the different types of gauges used in every industry:
- Plain Type Gauge
- Snap Gauges or Gap Gauges
- Ring Type Gauge
- Limit Type Gauge
- Pin Type Gauge
- Caliper Type Gauge
- Feeler Type Gauge
- Screw Pitch Gauges
- Radius or Fillet Gauge
- Taper Gauge
- Thread Gauge
- Form Gauge
1. Plain Plug Gauges.
Plain plug gauges are used for checking plain or unthreaded holes and shafts. These plain plug gauges are made of proper wear-resisting steel, and the handles are made of any suitable steel, such as light metal handles, always for heavy plain plug gauges, or suitable non-metallic handles are provided for smaller plain plug gauges.
The gauging surface of plain plug gauges is hardened to not less than 750 H.V and suitably stabilized, ground, and lapped.
The plain plug gauges are the double-ended type for sizes up to 63 mm and the single-ended types for sizes above 63 mm. The plain plug gauges are designated by ‘GO’ and ‘NOGO’ as applicable.
Types of Plain Plug Gauges in Normal Practice are
- GO and NO-GO plain plug gauges for sizes up to 10 mm.
- GO and NOGO plain plug gauges for sizes over 10 mm and up to 30 mm (Taper Inserted Type)
- GO and NO-GO plain plug gauges for sizes over 30 mm and up to 63 mm of fastener type.
- Go and NOGO plain plug gauges for sizes over 63 mm and up to 100 mm of fastener type.
- GO and NO-GO plain plug gauges for sizes over 100 mm and up to 250 mm of flat type. This is a shell form plug gauge. Each plug is relieved to reduce weight.
2. Snap Gauges or Gap Gauges.
A snap gauge consists of a plate or frame with a parallel-faced gap of the required dimension. In these gauges, the gauging anvil can be adjusted endwise to suit any particular limit dimension required.
The snap gauges are used for both cylindrical and non-cylindrical work, as compared to ring gauges, which are used only for cylindrical work.
Types of Snap Gauges
They are basically classified into two types,
- Rib-type snap gauges
- Plate snap gauges
#1. Rib Type Snap Gauges.
It is a double-ended type snap gauge that is used for checking sizes in the range of 3 mm to 100 mm, and single-ended progressive type snap gauges are suitable for the size range of 100 to 250 mm.
The gauging surface is hardened up to 720 H.V. and suitably stabilized, ground, and lapped. The other surfaces are finished smoothly.
#2. Plate Snap Gauges.
It is a double-ended type snap gauge used for sizes in the range of 2 to 100 mm, and a single-ended progressive type in the size range of 100 to 250 mm.
These plate snap gauges are usually made of wear-resistant steel of suitable quality. The gauging surfaces are suitably hardened, stabilized, ground, and lapped. Other surfaces are smooth-finished. The gauges are flat, and all sharp corners and edges are removed.
3. Ring Gauges.
A ring gauge is a precision inspection tool used to check the outer diameter of cylindrical parts, such as shafts and pins, by providing a simple, pass/fail result. It functions as a limit gauge, meaning it determines if a part’s external dimension is within a specified tolerance range without providing a specific measurement.
A complete set typically consists of two hardened steel rings: a go ring and a no-go ring. The go ring is sized to the upper limit of the part’s tolerance, while the no-go ring is sized to the lower limit.
By attempting to fit the go ring onto the part and the no-go ring onto the part, an inspector can quickly and reliably determine if the part meets the required specifications for size at the gauge plane.
This makes ring gauges invaluable for high-volume manufacturing, where they provide consistent and efficient quality control with minimal operator influence.
Types of Ring Gauges
There are three primary types of ring gauges from the functional perspective:
- Go ring gauges
- No-go ring gauges
- Master or set ring gauges
Go Ring Gauges
Go ring gauges are designed to verify the upper tolerance limit of the outer diameter of the part.
If the go ring gauge fits over the outer diameter of the part, then this indicates that the maximum allowable material condition for that part has not been exceeded, meaning that the diameter of the part falls within the upper limit of its tolerance, and therefore, the part is acceptable.
No-go Ring Gauges
No-go ring gauges check the lower tolerance limit on the outer diameter of the part. If the no-go ring gauge does not fit over the outer diameter of the part, then this indicates that the minimum allowable material condition for the part has been satisfied, meaning that the diameter of the part exceeds the minimum or lower limit of its tolerance, and therefore, the part is acceptable.
If the go ring gauge will not fit over the part being tested, the part diameter is too large, meaning that it contains excess material and should be rejected. Similarly, if the no-go ring gauge fits over the part being tested, then too much material has been removed, and the part falls below its minimum tolerance value, and similarly should be rejected.
When ring gauges are used to directly assess the acceptability of parts, the practice is known as direct gaging.
Master Ring Gauges
Master ring gauges, also called set ring gauges, are used for the mastering of other metering instruments.
These gauges may be used to set other measuring instruments, such as bore gauges or internal micrometers, for example, by providing a measurement standard or reference standard for calibration purposes. The practice is known as indirect gaging.
4. Limit Gauges.
Limit gauging is an inspection method employing specialised rigid gauges devoid of scales designed to assess the dimensions of manufactured components. These gauges do not provide actual dimension values; instead, they serve to ascertain whether a component falls within predetermined tolerance limits.
Unlike traditional measuring instruments, limit gauges solely determine whether a part is within or outside the specified tolerance zone without quantifying dimension values or indicating the magnitude of any errors in the component.
These gauges are designed with two critical components: a “go” side and a “no-go” side. The “go” side checks if the part’s dimensions meet the lower tolerance limit, while the “no-go” side verifies if the dimensions exceed the upper tolerance limit.
These are commonly known as “go” and “no-go” gauges, meticulously crafted to match the upper and lower limit sizes of the workpiece to be measured. In this design, one end of the gauge corresponds to the maximum permissible size, while the opposite end aligns with the minimum allowable size.
There are two main types of limit gauges: double-end and progressive. A double-end gauge features the “go” member at one end and the “no-go” member at the other. The “go” member must fit within or over an acceptable workpiece, while the “no-go” member should not.
In contrast, a progressive gauge houses multiple “no-go” members adjacent to each other and assesses a workpiece with a single motion. Some gauges, known as solid gauges, are designed for specific limit ranges and remain fixed, while others are adjustable to accommodate various ranges.
5. Pin Gauges.
When the holes to be checked are larger than 75 mm, such as an automobile cylinder, it is possible to use a pin gauge as shown in the figure.
During the measurement, the gauge is located lengthwise in the cylinder bore, and the measurement is done. These types of gauges are particularly useful in the measurement of grooves or slot widths.
6. Caliper Gauges.
A caliper gauge is similar to a snap gauge, but it is used to check both the inside and outside dimensions of the product. One end of the caliper gauge checks the inside dimensions (hole diameter), while the other end measures the outside dimensions (shaft diameter).
There are various categories for caliper gauges.
- Inside caliper – The inside dimensions of an object can be measured using inside calipers.
- Outside Caliper – Outside calipers are used to measure the size of an object from the outside.
- Divider caliper – A compass, divider, and caliper are all tools with two legs that pivot together at the top and are used to measure tiny distances.
- Odd Leg Caliper – It consists of two legs, one of which is bent to measure stepped surfaces.
- Vernier Caliper – A vernier caliper is a tool that measures the distance between two points on a linear scale. It can be utilized for depth, inner, and outer dimension calculations.
- Micrometer Caliper – Micrometer calipers are used to take exact measurements. Its name suggests that it has the lowest count, which is one micron, or 0.001 mm.
7. Feeler Gauge.
It is also known as a thickness gauge. Feeler gauges are often used to measure the clearance between the components.
These gauges are excellent for the measurement of narrow slots, measuring clearance, determining small spacing, and determining the fit between mating parts.
An extensive application of the filler gauge is to adjust the spark gap between the distributor points of a vehicle. These types of gauges are made of a set of narrow strips or blades of a sheet of marked thickness on each strip.
The whole set consists of strips of various thicknesses that are assembled. The width of each strip is commonly prepared up to 12.5 mm. During the usage, the blade must neither be forced nor slide smoothly between the mating parts.
8. Screw Pitch Gauges.
The screw pitch gauge is also called a thread gauge, which looks similar to a filler gauge. Each strip or blade has several teeth, precisely shaped in standard thread form.
They are used to check the pitch of screw threads. They are available with thread angles of 55° and 60°. The screw pitch gauges are similarly available in metric and inch pitches.
9. Radius or Fillet Gauge.
These gauge types are used to check the concave and convex radii on corners or shoulders. It is also useful for layout work and inspection of components in various industries. It is used as a template when grinding cutting tools.
10. Taper Gauge.
The taper gauge measures dimensions such as gap widths and groove depths, hole diameters, and pipe inner diameters. There are two types of taper gauges: plug and ring.
Aside from metal models, such as carbon tool steel and stainless steel. There are also plastic models that are durable. These gauges include a polycarbonate or brass casing or cover that makes them easy to carry.
11. Thread Gauge.
A thread gauge is used to determine the diameter and pitch of the thread. Thread gauges are often called screw-pitch gauges.
The internal threads of brushes and nuts are measured using plug thread gauges. In order to check the external thread of bolts and screws, ring thread gauges are used.
12. Form Gauge.
Form gauges are measurement tools made especially for evaluating an object’s profile. The radius gauge is the most common type of form gauge.
It is made up of a series of blades with different convex and concave circular profiles. They are employed for measuring groove radii as well as corners.