The Ultimate Guide To Micro Screw Thread Size Gages

A micro screw thread size gauge is a tool used to identify the size and pitch of screw threads, helping users distinguish between various screw sizes and types. These gauges are designed with small fasteners in mind and are useful for working with both metric and standard fastener sizes. They are often made of solid steel with zinc plating, making them durable and resistant to rust and corrosion. The gauges feature markings that are easy to read and won't peel off, ensuring long-lasting accuracy.

Thread gauges for nuts, bolts and screws

Thread gauges are used to identify the size and thread pitch of nuts, bolts, and screws. They come in a variety of materials, including plastic and metal, and can measure both external and internal threads.

Plastic gauges are a more inexpensive option for measuring external thread. They are solid and usually come in US and Metric measurements. For example, a US plastic gauge includes sizes #0 to 3/4" (coarse and fine), while a Metric gauge would include sizes 1.6mm to 16mm.

Metal gauges tend to be more premium and can measure both external and internal threads. They often come with detachable magnetic plates for convenient sizing.

Thread gauges come in a variety of sizes, with some being designed specifically for small fasteners. For example, a small metric gauge can measure sizes M1.2-0.25 to M3.5-0.35.

In addition to size, thread gauges can also measure the diameter and length of nuts, bolts, and screws. For instance, the Stainlesstown Nut Bolt Thread Gauge measures fractional bolts from size #4 to 1" up to 7" long and metric bolts and screws from 3mm to 22mm.

Thread gauges are a handy tool for anyone who regularly uses bolts, screws, or nuts, providing a simple way to measure and identify these fasteners.

Identifying thread pitch, tap size and drill bit size

Thread gauges are used to identify the size and pitch of nuts, bolts, and screws. They are available in different measurement systems, including fractional, metric, wire gauge number, and letter.

Fractional sizes are measured in inches, while metric sizes are measured in millimetres. The wire gauge and letter systems refer to tool diameters that increase as the wire gauge decreases from #107 to #1 and then continues from A to Z.

The thread pitch is the distance between threads and is measured in millimetres. The thread pitch can be determined by screwing a fastener into the slot of a thread gauge.

The tap size chart provides a list of standard tap sizes, specifying the diameter and thread spacing for fractional, metric, and screw sizes. The tap size chart also includes the recommended tap drill size for each standard tap size. This size drill bit should be used for drilling the initial hole that will then be tapped.

The drill size chart lists standard drill bit sizes in various measurement systems, including metric and English units. Metric drill bit sizes are indicated by the diameter of the bit in standard metric lengths, while letter drill bit sizes are indicated by letters, from size A (smallest) to Z (largest).

Coarse and fine threads

When selecting the right screw thread size gauge, it is important to understand the difference between coarse and fine threads. While there is no universal "better" option between the two, their unique characteristics make them suitable for different applications.

Coarse threads refer to fasteners with a low number of threads per distance along the fastener. They are thicker and more durable than fine-threaded hardware. Coarse-threaded fasteners can be installed more quickly and offer clearance for thread plating. They are also less likely to gall and strip, especially if the bolt is made of a soft material. Coarse threads are suitable for brittle applications such as plywood, OSB, and thin gauge metal.

On the other hand, fine threads have a larger number of threads per distance along the fastener. Fine thread fasteners have better strength characteristics due to their larger minor diameter values. They provide more connection points, which aid in pull-out performance. Fine threads are ideal for thick gauge metal applications and thicker, more robust metals. They offer superior resistance to vibration due to their smaller thread helix angles.

To measure the thread size, you can use a screw thread gauge, which helps identify the thread pitch, tap size, and drill bit size. For inch measurements, the thread size is specified by the diameter and threads per inch (TPI). For metric screws, the diameter is given in millimetres (e.g., M6 for 6 mm), and the thread size is specified by the pitch, which is the distance between threads in millimetres.

Standard and metric thread sizes

Screw thread size is an important consideration when selecting the right screw for a secure connection. The size refers to the dimensions of the threads on a screw, which determine how it fits into a threaded hole. There are several different systems of measurement used for screw thread sizes, including the Unified Thread Standard (UTS) and the metric system.

Unified Thread Standard (UTS)

The UTS, also known as Imperial, is used in the United States. Thread sizes in inches are specified by diameter and threads per inch (TPI). For example, a screw size of 10-24 indicates a thread diameter of 0.190" and 24 threads per inch. When the diameter is smaller than 1/4", the value is indicated by a number, such as #1 or No.1. Threads are measured by counting the number of thread peaks along a one-inch length.

Metric System

The metric system is used in most other countries and is growing in popularity in the U.S. Metric thread sizes are specified by diameter and pitch, which is the distance between threads. For example, an M6x1 screw has a diameter of 6 mm and a pitch of 1 mm. To measure the thread pitch, use a caliper to measure the distance between two adjacent threads at their peaks.

Choosing the Right Thread Size

When choosing the right thread size, it is important to consider the specific application and the type of fit required. For metric threads, if the pitch is unknown, it is recommended to choose coarse threads as they are the industry standard. Additionally, when selecting a screw for a threaded hole, ensure that the screw diameter matches the diameter of the hole for a secure and stable connection.

Storage and transportation

Micro screw thread size gauges are an essential tool for any precision engineering or manufacturing workshop. Due to their small size, they can be easily stored and transported, making them convenient for professionals and hobbyists alike. Here are some detailed guidelines for ensuring the optimal storage and transportation of these gauges:

Storage Solutions:

• Plastic Storage Boxes: Dedicated plastic storage boxes, such as the TwistPack, QuadroPack, or UniBox, are ideal for keeping your micro screw thread size gauges organised and protected. These boxes are designed to securely hold the gauges and can be labelled for easy identification.
• Colour-Coded Storage: Consider investing in a colour-coded storage system, especially if you work with a variety of fasteners. Colour-coding helps separate and organise different types of gauges, making it quicker to locate the specific micro screw thread size gauge you need.
• Looped Wire Lanyards: Micro screw thread size gauges with looped wire lanyards offer a convenient storage option. They can be clipped onto a belt, hung from a rack, or stored almost anywhere in your workspace, making them easily accessible.
• Storage During Use: When using a micro screw thread size gauge, it is important to ensure that it is not placed on a dirty surface or exposed to debris. Always keep a clean workspace and consider using a magnetic parts tray to hold the gauge when not in use, reducing the risk of loss or damage.

Transportation:

• Portable Cases: Some gauges come with carrying cases, which are ideal for transporting them. These cases protect the gauges from damage and keep them organised during travel.
• Protection from Elements: Micro screw thread size gauges should be protected from excessive heat, humidity, moisture, and corrosive chemicals. When transporting them, ensure they are stored in a dry, temperature-controlled environment to maintain their accuracy and longevity.
• Calibration and Maintenance: Regularly inspect and calibrate your gauges to ensure accuracy. Proper maintenance, such as cleaning and lubricating the gauges, is crucial to extend their lifespan and improve performance. Always clean and recoat gauges with a rust preventative solution or dip them in an easy-to-peel, oil-based wax coating after use.

Frequently asked questions