Common Knowledge of Screw Applications

Common Knowledge of Screw Applications

Selection of Screws

Based on the Usage Environment

• Humid Environments: In damp places such as outdoors and bathrooms, to prevent screws from rusting and corroding, stainless - steel screws or those treated with anti - rust processes like galvanizing or nickel - plating should be selected.
• High - Temperature Environments: In high - temperature areas like near engines or furnaces, heat - resistant alloy steel screws are required to ensure they can maintain their mechanical properties under high temperatures.
• Strongly Corrosive Environments: In environments with acid or alkali corrosion, such as chemical workshops, titanium alloy screws with good corrosion - resistance properties should be used.

Based on the Connected Materials

• Wood: For wooden materials, self - tapping screws are a good choice. Their threads can easily cut into the wood without the need for pre - drilling, and they can provide good fastening force.
• Metal: When connecting metal parts, the appropriate screws should be selected according to the hardness and thickness of the metal. For softer metals like aluminum alloy, ordinary machine screws can be used. For harder steels, stronger screws are needed, and pre - drilling and tapping may be required.
• Plastic: Since plastic is relatively soft, screws specifically designed for plastic, such as plastic self - tapping screws, should be used. Their thread design can prevent the plastic from cracking.

Based on the Required Connection Strength

• General Connections: For applications with low requirements for connection strength, such as furniture assembly or fixing the casings of common electrical appliances, ordinary - specification screws can be selected.
• High - Strength Connections: In fields with extremely high requirements for connection strength, such as mechanical manufacturing and bridge construction, high - strength bolts like grade 8.8 and 10.9 are needed. These bolts have undergone special heat - treatment processes and have high tensile strength and yield strength.

Based on the Installation Space

• Narrow Spaces: When the installation space is limited, screws with smaller heads, such as countersunk head screws or socket head cap screws, should be chosen. Countersunk head screws sit flush with the surface after installation, not taking up extra space. Socket head cap screws can be operated with smaller tools, which is suitable for tightening in narrow spaces.
• Open Spaces: In situations where the space is relatively spacious, screws with ordinary heads can be selected for more convenient installation operations.

Installation of Screws

Tool Selection

• Screwdrivers: For Phillips - head and slotted screws, a suitable screwdriver should be selected according to the size of the screw slot to ensure a perfect fit, avoiding damage to the screw slot during the tightening process.
• Wrenches: For hexagon - head screws and nuts, wrenches of the corresponding specifications are needed for tightening. Common types of wrenches include open - end wrenches, box wrenches, and socket wrenches, and the appropriate type should be chosen according to the actual situation.
• Power Tools: In large - scale production or when rapid installation is required, power tools such as electric screwdrivers and electric wrenches can improve installation efficiency. However, when using power tools, attention should be paid to controlling the torque to avoid over - tightening or under - tightening.

Installation Steps

• Clean the Installation Area: Before installing the screw, ensure that the surface of the connected materials is clean, flat, and free of oil, debris, etc., as these may affect the fastening effect of the screw.
• Position and Drill Holes (if necessary): For screws that require pre - drilling, a suitable drill bit should be used to drill holes according to the screw specifications and the nature of the connected materials. The diameter of the drilled hole should match the screw diameter, and the depth should be appropriate.
• Insert and Tighten the Screw: Insert the screw into the hole and slowly tighten it with a tool. During the tightening process, keep the screw perpendicular to the connected materials to avoid poor fastening caused by the screw being tilted. For some important connection parts, the screw should be tightened according to the specified torque value, and a torque wrench can be used to control the torque.

Removal of Screws

Tool Preparation

Removal Methods

• Normal Removal: Use the same tools as for installation and rotate the screw in the opposite direction to unscrew it. During the removal process, pay attention to using moderate force to avoid damaging the screw or the connected materials.
• Handling Rusted or Stuck Screws: If the screw is rusted or stuck, first spray a rust remover or lubricant on the screw and wait for some time to allow it to penetrate into the threads, then try to remove the screw again. If it still cannot be removed, the heating method can be used to expand the screw, which may sometimes help to unscrew it smoothly. However, pay attention to controlling the temperature during heating to avoid damaging the surrounding materials.

Maintenance and Care of Screws

• Regular Inspection: Regularly inspect the parts connected by screws to check for any signs of looseness, rust, or damage. If problems are found, they should be addressed promptly.
• Anti - Rust Treatment: For screws prone to rusting, anti - rust oil can be applied regularly or other anti - rust treatments can be carried out to extend the service life of the screws.
• Avoid Overuse: When using screws, avoid exceeding their load - bearing capacity to prevent the screws from deforming or being damaged. Also, do not frequently disassemble and install the screws to avoid wearing the threads.