Basic Assembly Work

Using Tools Incorrectly Usually Hurts Yourself

Most injuries on the assembly line come not from large equipment, but from spanners and hammers. A spanner slips and tears the palm of your hand on the bracket's edge, or when you force a pipe in and apply force, the bolt suddenly breaks, causing you to fall back due to the recoil.

Tools are not tools that make things move, but tools that precisely transmit a set amount of force. The moment you force them, the tool, the part, and even you yourself get damaged.

Spanner/Wrench — "Pulling" Is the Principle

Four Rules to Follow

1. Do not push, pull instead. If you push and the bolt suddenly loosens, your hand will hit the structure in front of you. Pulling makes you move backward, which is much safer.
2. Do not extend with a pipe. The torque doubles, causing the bolt to break or the tool to crack. If you lack power, use a longer size tool or an impact wrench instead.
3. Use the 6-sided box wrench first. 12-sided wrenches have greater angular freedom but narrow contact surfaces, making it easy to deform the angle. The more stubborn the bolt, the more you should use the 6-sided one.
4. Hold the wrench so that the force goes toward the fixed jaw. If you hold it the other way, the adjustable jaw will open and slip.

Hidden Pitfalls of Slightly Different Sizes

[Size Generation Differences]
M10 bolt head width:  16mm (ISO)  /  17mm (Old DIN)
M12 bolt head width:  18mm (ISO)  /  19mm (Old DIN)

[Inch and Metric Mix]
13mm spanner → fits 1/2 inch (12.7mm) bolt with 0.3mm looseness
                      After several uses, the angle becomes rounded

> In workplaces where imported equipment, old equipment, and overseas supplier parts are mixed, metric and inch, ISO and DIN coexist on the same line. If it feels loose, don't force it; find the correct tool instead. A bolt with a deformed angle can take several hours to remove.

Hex Wrench and Socket

• The rounded (ball-point) side is only for reducing the angle. Due to the small contact surface, using it for final tightening will deform the hex hole. Always use the straight side for the final tightening.
• Impact sockets are black (chromoly), and hand sockets are polished chrome (chromvanadium). If you use a polished socket with an impact wrench, it will break and send fragments flying. You can distinguish them just by color.
• If the socket does not fully fit into the bolt, applying force will deform the angle. Push it in and shake it once to check.

Driver — If the Size Doesn't Match, the Screw Dies

Inserting a PH driver into a PZ screw makes the contact point-like, which can damage the screw head. If you see a line on the screw head, it's a PZ screw.

• Apply about 70% pressing force and 30% rotating force. If you don't press enough, cam-out will occur.
• Do not use the driver as a lever or puller. If the shaft bends, it will never go straight again.
• When using an electric driver, set the clutch count definitely before starting. Using it at maximum can break plastic parts.

Hammer — The Simplest and Most Dangerous Tool

Three Things Leading to Accidents

1. Loose handle wedge → The head flies off during striking. Before use, hold the head and shake it to check.
2. Mushrooming of the striking face → The edge is compressed and expanded. This becomes fragments that fly into your eyes. Replace or reshape the hammer or mallet immediately.
3. Do not strike hammers against each other — Both are hard and will definitely break.

Gloves with oil on them are slippery. Safety goggles are essential for striking work.

Pliers

Long nose, nippers, and vise grips are tools for gripping and cutting, not for tightening. Tightening a nut with pliers will deform the angle, making it hard for the next person to loosen. When doing electrical work, only use those with insulated handles (with voltage rating).

Common Mistakes by Newcomers and Their Consequences

Tool Inspection Before Starting Work

• Does the hammer head not wobble (wedge condition)
• Has the striking face or end of the mallet not mushroomed out
• Is the tip of the driver blade not worn or deformed
• Is the internal corner of the socket not rounded from wear
• Is the insulation of the insulated tool not peeled off
• Is the tool in the correct position (3 Standards: Genuine, Quantity, Position)

> If tools are left anywhere on the assembly line, the next person can't find them, and the line stops. This is why we use shadow boards (tool silhouette displays). It makes missing spots clearly visible and prevents accidents where tools are left inside the product during assembly.