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Commonly Used Screw Sizes in Manufacturing: Quick Reference Chart by Standard
Introduction
In the manufacturing field, screws are the unsung heroes behind the scenes. They may not stand out, but they are essential components in assembling machines and products. Without screws, everything around us—cars, home appliances, furniture—would fall apart.
The role of screws is not merely to hold parts together. By selecting the right screws and fastening them properly, you can ensure the safety and durability of a product. On the other hand, using the wrong screws or failing to tighten them adequately can lead to product failures or even accidents.
The basics of screw selection revolve around three key elements: size, standard, and material.
- Size: Choose based on the thickness of the part and the size of the screw hole.
- Standard: Select according to the usage scenario, such as metric or inch screws.
- Material: Choose from steel, stainless steel, titanium, etc., depending on the environment and required strength.
Making a comprehensive judgment based on these elements is the first step in quality control within the manufacturing process.
This article provides a comprehensive guide to commonly used screws in manufacturing settings, focusing on a quick reference chart categorized by standards. It also covers types, uses, tightening torque, materials, and strength. We hope this information deepens your understanding of screws and supports your daily operations.
1. Screw Sizes and Standards
Screw sizes and standards vary widely depending on the application. Below are quick-reference tables for representative screw standards commonly used in manufacturing.
Metric Screws (M Screws)
Metric screws, measured in millimeters, are widely used in Japan and Europe. They conform to the JIS B 0205 standard.
Quick Reference: Common Metric Screw Sizes
| Nominal Diameter (M) | Pitch (mm) | Typical Tool Size (mm) |
|---|---|---|
| M3 | 0.5 | 5.5 |
| M4 | 0.7 | 7.0 |
| M5 | 0.8 | 8.0 |
| M6 | 1.0 | 10.0 |
| M8 | 1.25 | 13.0 |
| M10 | 1.5 | 17.0 |
| M12 | 1.75 | 19.0 |
Inch Screws
Inch screws are measured in inches and mainly used in the United States and the United Kingdom. Standards include Unified threads (UNC/UNF) and Whitworth threads (BSW).
Quick Reference: Common Inch Screw Sizes
| Nominal Diameter (inch) | Pitch (threads/inch) |
|---|---|
| 1/4 | 20 (UNC) |
| 1/4 | 28 (UNF) |
| 3/8 | 16 (UNC) |
| 3/8 | 24 (UNF) |
| 1/2 | 13 (UNC) |
| 1/2 | 20 (UNF) |
Pipe Threads
Pipe threads are used for sealing fluid lines and pipes. There are two main types: taper threads (R/PT) and parallel threads (G/PF).
Quick Reference: Common Pipe Thread Sizes
| Nominal Diameter | Pitch (mm) |
|---|---|
| R1/8 | 0.907 |
| R1/4 | 1.337 |
| R3/8 | 1.337 |
| R1/2 | 1.814 |
Other Screw Standards
Besides the above, there are many other screw standards tailored to specific applications. Refer to specialized documents as needed.
2. Types and Uses of Screws
Screws come in many types depending on shape and application. This section introduces both general-purpose screws and those used for specialized manufacturing needs.
Common Screw Types
| Type | Application | Characteristics |
|---|---|---|
| Wood Screws | Joining and fixing wood | Threaded along the shank with a pointed tip. Designed to be screwed directly into wood. |
| Tapping Screws | Form threads in metal or plastic as they are driven in | No need for pre-drilled holes. Efficient fastening. |
| Bolts | Used with nuts | Provides strong fastening. Suitable for securing machine components. |
| Machine Screws | Assembly of machines or electronic devices | Small heads with various shapes available. |
Special-Purpose Screws
| Type | Application | Characteristics |
|---|---|---|
| Self-Drilling Screws | Used for fastening metal sheets | Drill-shaped tip eliminates the need for pre-drilling. |
| Coarse Thread Screws | Used for rough wood assembly or fixing gypsum boards | Coarse pitch provides strong grip in wood. |
| Others | Special-purpose screws for various needs | Refer to specialized documents as needed. |
3. Screw Tightening Torque
Tightening torque is crucial for preventing screws from loosening or breaking, thereby ensuring product safety. Applying the correct torque allows screws to perform at their full potential.
Importance of Tightening Torque
- If the torque is too low, the screw may loosen and the part may detach.
- If the torque is too high, the screw or part may be damaged.
Basic Torque Formula
Tightening torque is calculated using the following formula:
Torque (T) = Torque Coefficient (K) × Screw Diameter (d) × Axial Force (F)
- Torque Coefficient (K): A value determined by the screw material and surface treatment
- Screw Diameter (d): The nominal diameter of the screw
- Axial Force (F): The clamping force applied by the screw
Quick Reference: Recommended Torque by Screw Size
| Screw Size | Recommended Torque (N·m) |
|---|---|
| M3 | 1.0–1.5 |
| M4 | 2.5–3.5 |
| M5 | 5.0–6.0 |
| M6 | 8.0–10.0 |
| M8 | 20.0–25.0 |
| M10 | 40.0–50.0 |
*The above values are for reference only. Actual torque values may vary depending on material, condition, and operating environment.
Precautions for Torque Management
- Use a torque wrench to apply the appropriate torque.
- Calibrate the torque wrench regularly to maintain accuracy.
- Select the appropriate torque based on the material, condition, and usage environment.
- After fastening, check the torque regularly to ensure screws remain tight.
4. Screw Materials and Strength
Screw materials and strength must be selected according to environmental and load conditions.
Common Screw Materials
| Material | Characteristics | Applications |
|---|---|---|
| Steel Screws | Common and inexpensive. High strength but prone to rust. | General mechanical products, construction materials, etc. |
| Stainless Steel Screws | Excellent corrosion resistance. Resistant to rust and extreme temperatures. | Outdoor products, food machinery, medical devices, etc. |
| Titanium Screws | Lightweight with high strength. Excellent corrosion and heat resistance. | Aerospace equipment, medical devices, sporting goods, etc. |
Screw Strength Grades
Screw strength grades are defined by JIS standards. These grades are indicated by numbers stamped on the screw head.
JIS-Based Strength Grades
| Strength Grade | Tensile Strength (N/mm²) | Yield Strength or Proof Stress (N/mm²) |
|---|---|---|
| 4.8 | 400 | 320 |
| 8.8 | 800 | 640 |
| 10.9 | 1000 | 900 |
| 12.9 | 1200 | 1080 |
Higher strength grades allow the screw to withstand greater loads. Choose the appropriate grade according to the usage conditions.
Summary
Screw selection in manufacturing is a key factor that affects product quality, safety, and durability. By selecting the right screws and using them properly, you can maximize performance and minimize the risk of accidents or failures.
Conclusion
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