ACTION 08

Fastening

Tightening two already-mated bodies to a specified preload

Why It Matters

Fastening is the final step of assembly and the one on which quality accountability rests. Examples include pre-tightening before a power tool applies final torque, driving screws in field assembly, and re-tightening bolts on racks and frames.

Dedicated nutrunners are limited to lines with fixed fastening positions. In high-mix assembly and field maintenance, where positions change from job to job, the work is done by hand and with tools, finding the preload window as the fastener turns.

Skills 4

08-ABare-Hand Fastening

The fastener must be turned by grip alone without a tool, and the required torque keeps increasing as it turns, so the grip must keep pace.

Bare-Hand Fastening — Initial state
Initial stateA fastener is started in its counterpart with no preload applied.
Bare-Hand Fastening — Final state
Final stateThe fastener is tightened by hand to the specified preload.
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08-BScrewdriver FasteningTOOL

The screwdriver must be pressed and turned while held perpendicular to the surface, and the slightest tilt of its axis lets the tip slip out of the recess and wears the fastener.

Screwdriver Fastening — Initial state
Initial stateA fastener is started in its counterpart, and a screwdriver is held in hand.
Screwdriver Fastening — Final state
Final stateThe fastener is tightened to the specified preload without damage to its drive recess.
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08-CHex Key FasteningTOOL

The turning force acts at the end of the handle, away from the axis, and tilts the tool, so it must be turned while keeping the angle at which it sits in the socket.

Hex Key Fastening — Initial state
Initial stateA fastener is started in its counterpart, and a hex key is held in hand.
Hex Key Fastening — Final state
Final stateThe fastener is tightened to the specified preload without the tool slipping out.
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08-DWrench FasteningTOOL

The tool grips only the outer faces of the fastener, so the slightest deviation in turning direction makes it slip off and damage the corners.

Wrench Fastening — Initial state
Initial stateA fastener is started in its counterpart, and a wrench is held in hand.
Wrench Fastening — Final state
Final stateThe fastener is tightened to the specified preload without damage to its corners.
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