月: 2023年3月

What Is a Point Tap?

A point tap, also known as a gun tap, is a specialized threading tool designed for threading through holes. It features a twisted and sharp tip.

Due to its twisted and sharp tip, point taps produce chips in a forward direction, preventing chip blockage in the hole. This makes it ideal for trouble-free continuous machining on machines, ensuring stable tapping in mass production scenarios.

However, it is important to note that point taps are not suitable for tapping when a hole has a bottom.

Uses of Point Taps

Point taps find their primary use in machining, especially for large-volume through-holes and continuous machining of mass-produced items.

One of their key advantages is their lower cutting load compared to other taps, resulting in fewer issues like tap breakage and faster processing times. As a result, point taps are preferred in situations where increased productivity and maximum output within a limited timeframe are desired for mass-produced items.

Another benefit of point taps is their resistance to becoming dirty after processing, making it easy to clean both the jig and the final product.

Principles of Point Taps

Unlike hand taps and spiral taps, the tip of a point tap features grooves that direct chips along the blade’s direction. The tap’s design allows chips to slide down these grooves smoothly.

On the other hand, because the tip’s biting portion is cut deeper, point taps cannot reach the bottom of a hole with a hole bottom, and the chips tend to block the hole due to their forward discharge. This makes point taps unsuitable for machining stop holes.

In contrast, spiral taps have spiral-shaped blade grooves that discharge chips in the opposite direction of the tap, preventing chip interference during machining.

Point taps come in two material types: high-speed tool steel (HSS) and cemented carbide. HSS is known for its toughness and resistance to breaking, while cemented carbide is wear-resistant and maintains durability even after continuous machining. Material selection should match the processed material to ensure compatibility.

What Is a Threaded Connection?

A threaded connection (threaded joint, screw joint, screwed fitting) is a type of pipe fitting.

A pipe fitting is a component used to connect, branch, and close pipes. There are four major types of pipe fittings: threaded connection, welded connection, flanged connection, and ferrule connection.

Threaded connection is one of the four types that can be connected without using special tools or equipment. As a relatively inexpensive piping joint, it is used in a wide range of fields, including power generation and chemical plants, factories, building facilities, and general households.

Applications of Threaded Connection

Figure 1. Example of screwed joint use

Threaded connection is mainly used to connect, branch, and close pipes during piping installation. In most cases, piping routes do not follow a straight line along their entire length, and there are cases in which a pipe route is curved up, down, left, or right, or a single pipe route is branched into two to four pipes, or vice versa, and then assembled. In such cases, threaded connections are required.

Threaded connections are used in many situations in factories, machinery, and homes. However, threaded connections are generally used in piping for low-pressure fluids. For fluids such as high-pressure, high-temperature steam, etc., the possibility of accidents or damage due to leakage exists, so fittings such as plug-in fittings or welded fittings should be used.

As an example, in JIS B2301 threaded malleable iron pipe connection, the maximum working pressure is specified as follows:

Fluid state	Max. working pressure
Static water at 120°C or less	2.5 MPa
Steam, air, gases, and oil up to 300°C	1.0 MPa

Principles of Threaded Connection

Threaded connection has a pipe thread machined on one or both ends of the part. The thread shape is specified by various standards, and the typical types are as follows.

Standard	Standard No.	Standard Name
ISO	228-1	Pipe threads where pressure-tight joints are not made on the threads – Part 1: Dimensions, tolerances and designation
	7.1	Pipe threads where pressure-tight joints are made on the threads – Part 1: Dimensions, tolerances and designation
ANSI / ASME	B1.20.1	Pipe threads or general -purpose inch
		NPS: American National Standard Straight Pipe Threads
		NPT: American National Standard Taper Pipe Threads

Tapered pipe threads have a thread outside diameter that decreases toward the tip for male threads and toward the depth of the hole for female threads. For parallel pipe threads, the thread outside diameter is the same over the entire length of the thread for both male and female threads.

Threaded connection prevents leakage of fluid by ensuring that the male and female threads are tightly fitted together. Generally, when used as a fitting for piping, tapered pipe threads are used in many cases because they are more tightly sealed than parallel pipe threads. Sealing tape can be wrapped around the threads or sealing material can be applied to further improve sealing. See figure 2 below for a close fit of the male and female threads.

Figure 2. Principles of taper screw

The two types of parallel pipe threads and tapered pipe threads are selected in the following combinations according to the application and required tightness.

Combination of threads		Male thread
		Tapered pipe thread (R)	Parallel pipe thread (G)
Female thread	Tapered pipe thread (Rc)	◎	×2
	Parallel pipe thread (Rp)	◎	×2
	Parallel Thread for Pipe (G)	×1	〇1

Symbol Description
◎: Can be combined with sealing tape for tight joints such as piping.
〇1: Mechanical joints can be combined by using packing or gasket together.
×x1: Combination is not possible due to the possibility of leakage caused by damage to the parallel threads or packing.
×x2: Depending on the screw manufacturing tolerance, it may not be possible to screw in, so sealing cannot be achieved, and the combination is not possible.

Types of Threaded Connections

There are several types of threaded connections depending on the application and direction.

1. Threaded Connections Standards

Standard threaded connections are specified in terms of dimensions, shape, material, and range of application in each standard. Refer to the table below for the various standards of threaded connections.

Standard	Standard No.	Standard Name
JIS	B2301	Threaded malleable cast iron pipe fittings
	B2302	Threaded connections for steel pipes
	B2303	Threaded drainpipe joints
	B2308	Stainless steel threaded connections
ISO	4144	Pipework – stainless steel fittings threaded in Accordance with ISO 7-1

Types of JIS B2301
There are many types of threaded connections, and examples of JIS B2301 are shown in the table below. Refer to figures 2 and 3 for their shapes.

Type		Uses
Elbow	90° elbow	For changing the piping route to 90° or 45°
	45° elbow
	Different diameter elbow
	Male and female elbows (street elbows)
	45° Male and female elbows (45° street elbows)
	Male elbow with different diameter (different diameter street elbow)
Tee (cheese)	Tee with the same diameter	Branching (or gathering) piping routes in three directions
	Different-diameter tee
	Three-way different-diameter tee
Cross	Same diameter cross	When branching (or assembling) piping routes in 4 directions
	Different diameter cross
Sockets	Sockets with the same diameter	When joining pipes with male threads
	Different diameter sockets
	Female male socket
Bushing		When joining female threaded connections and pipes of different diameters
Nipple	Same diameter nipple	For joining threaded connections with female threads
	Different diameter nipple
Cap		To close a pipe with male threads
Plug		To close a female threaded connection
Union	Same diameter union	When female threaded connections are joined and need to be separated
	Female male union
	Union Elbow
	Male Male union elbow

Figure 3. Types of screwed joints (1)

Figure 4. Types of screwed joints (2)

Various sizes are available for each type, and are selected according to the pipe nominal diameter. 

2. Specifications and Sizes of Threaded Connections

Product specifications and sizes of threaded connections are defined by JIS standards and are indicated as follows.

	Standard No. or Standard Name	Type	Shape	Surface condition	Joint nominal
Example 1	JIS B 2301	Type I	Male and female elbows, different diameter	black	2 x 3/4
Example 2	Threaded malleable iron pipe fitting	Type I	45° elbow	plated	1-1/2

What Is a Small Ball Bearing?

Small ball bearings, also known as miniature bearings, are compact bearings with an outer diameter of less than 9 mm or an outer diameter of 9 mm or more, and an inner diameter of less than 10 mm. They play a crucial role in reducing friction and maintaining the position of rotating shafts, thereby protecting the components that support rotation. Due to their critical function in many machines with rotating shafts, they are sometimes referred to as the “rice of industry”.

Applications of Small Ball Bearings

Small ball bearings are utilized in a wide range of products, including home appliances, office automation equipment, and hobby equipment. The demand for these bearings is growing rapidly in all industrial fields, driven by the trend towards smaller, lighter, and thinner products. They are found in everyday items such as fishing reels, mini 4WDs, computer hard disk spindle motors, and copier paper feed rollers. Additionally, they are instrumental in downsizing medical equipment and various measuring devices, with applications extending to potential meters, gyro gimbals and rotors, polygon scanner motors, encoders, high-frequency spindles, VTR cylinders, and capstans.

Principle of Small Ball Bearings

The operational principle of miniature bearings is the same as that of standard bearings. They are typically rolling bearings, which include rolling elements like small balls or cylindrical rollers. These elements roll within the bearing, reducing friction and facilitating smooth rotation.

1. Rolling Bearings

Rolling bearings reduce friction by allowing rolling elements to move within the bearing as the shaft rotates. This action helps in supporting the shaft and minimizing friction during operation.

2. Plain Bearings

Unlike rolling bearings, plain bearings (such as bushes) do not contain rolling elements. They rely on materials and lubricants resistant to wear and seizure to support rotational movements. Plain bearings can support larger loads due to their line contact support mechanism, compared to the point contact in ball bearings.

Other Information about Small Ball Bearings

Material of Small Ball Bearings

Small bearings are typically made from heat-treated alloy steel, with high carbon chrome steel used for the inner and outer rings and the balls, and various materials like steel plates, stainless steel, or resin for the cage. Plastic bearings, which can operate without lubrication and are resistant to rust and chemical corrosion, offer an alternative, though they generally have a lower load capacity. Plastics used in these bearings include phenolic resin, PTFE (Teflon), PEEK, PPS, PCTFE (Daiflon), and PP. However, bearings with carbon have high environmental resistance but are not suitable for applications involving high impact, vibration, or insulation requirements due to their conductivity.

What Is a Unified Thread Standard?

A unified thread standard is an inch-based threading system with standardized basic dimensions in inches and a 60° thread angle.

While metric screws are standardized in metric units, the unified thread standard, including the witt screw, represents inch-based screws. For more information, visit inch screws on Metoree.

Uses of Unified Thread Standards

Unified thread standards are commonly used in aircraft, automobiles, and motorcycles. They are also prevalent in measuring instruments and industrial robots manufactured internationally, particularly in the United Kingdom, the United States, and Canada.

These standards are occasionally used in domestic equipment, primarily when the components are manufactured abroad.

Principles of Unified Thread Standards

The principle of the unified thread standard is similar to that of standard screws. Utilizing the screw’s slope, a heavy object can be lifted with minimal tightening torque, creating a significant fastening or axial force.

The screw remains secure due to the frictional force on the slope, which exceeds the gravitational slope component, thereby maintaining the fastening force. The thread angle of both unified and metric screws is 60°. However, the witt screw has a 55° thread angle.

Types of Unified Thread Standards

Similar to metric screws, unified thread standards come in two types: coarse (UNC) and fine (UNF). The primary difference lies in the thread pitch, with fine threads having more threads per inch than coarse threads. The denser arrangement of fine threads makes them less prone to loosening but requires more turning for tightening, making them less suited for mass production.

Other Information on Unified Thread Standards

Notation of Unified Thread Standards

Unified thread standards are denoted by labels such as UNC and UNF, as well as by fractions. Below is a guide to understanding these notations with an example.

Example: 3/8 – 20UNC x 5/8

1. 3/8: Thread Nominal (thickness)
This refers to the screw’s thickness, including the threads. In inch threads, this measurement is typically expressed as a fraction with 8 as the denominator.

2. 20: Number of Threads Per Inch
This represents the number of thread peaks within a one-inch length. For screws shorter than 1, the thread count is extrapolated to a one-inch length.

3. UNC: Thread Type (Coarse or Fine)
This indicates whether the thread is coarse (UNC) or fine (UNF).

4. 5/8: Length Below the Screw Head
Expressed in fractions of an inch, this length is measured from the base of the screw head to the end of the screw. It includes the length of the unthreaded shank. In tapered head screws, this length corresponds to the total length of the screw.

While the notation generally follows this format, there are unique terms for thread sizes. The thread designation, indicating the screw’s outer diameter, starts with the thinnest (e.g., #0, #1) and goes up to #12.

For sizes larger than #12, the diameter is represented by fractions of an inch, divided into eighths or quarters. These fractions are colloquially referred to as follows:

• 1/8: one eighth
• 1/4: two eighths (or one quarter)
• 5/8: five eighths
• 5/32: five thirty-seconds
• 5/16: five sixteenths

What Is an End Mill?

An end mill is a cutting tool used in industrial milling applications. It is known for its ability to produce minimal chips during cutting and is particularly effective in machining threads in soft materials. The strength of the threads produced is high, and the effective diameter variations are well-controlled.

End mills come in various designs, some featuring a groove to enhance the supply of cutting fluid.

Uses of End Mills

End mills are commonly used for soft materials like aluminum. While there are end mills designed for steel, they are less effective for harder materials. They are typically used in machine tools rather than by hand due to the high torque required during machining. They are particularly effective for machining stop holes where chip production is a concern.

Various manufacturers provide end mills for machining materials like iron, low carbon steel, low carbon alloy steel, and stainless steel.

Principles of End Mills

End mills work by forming threads through plastic deformation, making the size of the pre-hole crucial for the final thread shape. High-precision control of the pre-hole is essential. For instance, while a M10 x 1.5 thread machined with a spiral or point tap might require a Φ8.5 pre-hole, an end mill would require around Φ9.2.

Using a precise carbide drill is key to achieving high-precision pre-holes. For small-diameter holes with strict dimensional control, high-precision drills are recommended.

For achieving stable, high-precision drilling, using end mills for contouring or boring after pre-drilling with a drill is effective.

It is important to note that end mills are specific to either through-hole or stop-hole drilling and are not interchangeable. Rigid tapping, as opposed to using a tapping collet, is necessary due to the high torque required, ensuring stable thread depth.

What Is an Air Gripper?

An air gripper is a mechanical device used to hold the inner surface of a workpiece. It operates by expanding a hollow, cylindrical piece of rubber into a doughnut shape when air is injected into it, creating friction to hold the item. Similarly, a gripper that holds the outer surface of a workpiece using this principle is also referred to as an air gripper.

With a broad range of applicable inner diameters (e.g., φ16~21), a single air gripper can handle multiple types of workpieces. Materials used include chloroprene rubber, with silicone as an option for high-heat resistance applications or in the food industry.

Uses of Air Grippers

Air grippers are utilized in the transportation of objects like glass bottles, PET bottles, cans, and printer drums, which can only be handled from the inside. They are also employed in air leak testing for automotive components such as fuel tanks and mufflers, as well as in pumps.

These grippers are advantageous in handling and transporting rolled products like saran wrap, thanks to their ability to grip workpieces of varying diameters with a single size. They are widely used in the end-effectors of industrial and cooperative robots, particularly for gripping the insides of objects.

The silicone variant is chemically stable, exhibiting low temperature dependence and excellent resistance to extreme temperatures. It’s commonly used in the transportation of sensitive materials such as food and garments.

Principles of Air Grippers

Air grippers can grip and release workpieces weighing up to 70 times their own weight. This is achieved by rapidly and reliably injecting and exhausting air, without damaging the workpiece’s surface.

The concentric expansion of the rubber component accommodates workpieces of various diameters using a single size. This versatility reduces the time spent on changing chucks.

However, care is necessary as the rubber can crack or leak over time due to wear or exposure to harsh conditions. Regular checks are needed to avoid damage from sharp objects, UV deterioration, or environmental mismatches.

When dealing with workpieces with low friction coefficients, surfaces covered in substances like oil or water, or shapes prone to slipping, a sufficient safety factor is crucial due to the reliance on friction for holding. The clamping force can be adjusted for fragile parts using an air regulator.

What Is a Dust Monitor?

A dust monitor, also known as a dust analyzer, is a device used to measure particulate matter in gases. These devices, commonly referred to as dust meters, are employed in monitoring air quality in various environments, including workplaces and building management systems.

Another related device is the particle counter, which measures particulate matter in gases in environments requiring higher cleanliness levels, such as pharmaceutical and medical device manufacturing clean rooms, and in isolators used for quality control.

Uses of Dust Monitors

Dust monitors are typically used in areas with a noticeable presence of airborne particles, contrasting with particle counters designed for cleaner environments. They are ideal for general indoor or outdoor spaces where cleanliness levels are not strictly controlled, as well as in more particle-dense settings like factories.

These monitors are also crucial in measuring fine particulate matter like PM2.5 in the air. However, measuring oil mists and similar substances can be challenging due to potential contamination inside the equipment and varying responses to different types of mists.

Principles of Dust Monitors

Dust monitors utilize various measurement methods, with light scattering and piezobalance (piezoelectric balance) being the most prominent. The light scattering method, which involves measuring scattered light when it interacts with particles in a gas, is a commonly used technique in dust measurement. The amount of scattered light correlates with dust concentration, providing a basis for estimation.

However, the light scattering method assumes uniformity in particle properties. While this allows for consistent measurements when the assumption holds true, mixed particle properties necessitate verification of the measurement’s validity each time.

Conversely, the piezobalance method determines dust concentration by measuring the mass of particles collected on a balance. This method’s advantage lies in its independence from particle properties. The drawback is the need for regular cleaning due to the balance’s limited particle collection capacity.