Turning Tools

Everything in this lesson is torque: force applied at a distance from a center, so it is the torque lesson with a handle on it. Which tool is right usually comes down to how well it grips and how much leverage it gives.

Wrenches

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Box end over open end is the topic's central comparison. Six points of contact spread the load around the whole head; two flats concentrate it and let the wrench slip and round the corners off. If a question offers both and the fastener is tight, the box end is correct.

An adjustable wrench is the answer to almost no question. Its movable jaw flexes under load, so it grips worse than an open end wrench of the right size. It is what you use when you do not have the right size.

A pipe wrench is for round work. Its teeth bite in and its jaw tightens as you pull. Using one on a nut destroys the nut, and that is a question.

A 12-point socket fits a six-point fastener in twice as many positions, which helps in cramped spaces, but a six-point socket grips better on a tight or rounded fastener.

Leverage

A longer handle applies more torque for the same effort, which is the torque lesson exactly: torque is force times the distance from the center.

That is also why a long handle is dangerous. It is easy to exceed what the fastener can take and snap it, which is the reason torque specifications exist.

Ratchets and drives

A ratchet turns the fastener one way and free-wheels the other, so the tool never leaves the work. Its drive size names the square that holds the socket: 1/4 inch for small work, 3/8 inch for general work, 1/2 inch for heavy work.

A breaker bar exists because a ratchet's mechanism is the weak point. The pawls inside will fail before the steel does, so the heavy first pull gets a solid bar and the ratchet does the spinning afterward.

Screwdrivers

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Phillips cam-out is deliberate and it is a question. The tapered flanks push the driver out of the recess once torque gets high, which protected assembly line work from overtightening before torque-limiting drivers existed. It also explains why a Phillips screw chews up so readily.

A screwdriver tip should match the screw in both type and size. A flat tip that is too narrow concentrates force on part of the slot and twists it out, and one that is too wide damages the work around the screw.

A screwdriver is not a pry bar or a chisel, and using it as one is both the common shop error and the common exam distractor.

Know it by sight

What you can skip

Across the 58 questions on this topic in our bank:

• Specialty wrenches - spanner, crowfoot and strap wrenches - never appear; the flare nut wrench comes up once.
• Driver standards beyond the four tip shapes. Pozidriv and spline drives never appear. Slotted, Phillips, Torx and Robertson are the set.
• Torque specifications. No question asks for a torque value. The torque questions ask what the wrench is for and why fasteners are tightened to a specification.

Where people lose points

Choosing an open end wrench for a tight fastener. A box end grips six corners.

Treating an adjustable wrench as equivalent. It is a substitute, not a peer.

Using a pipe wrench on a nut. It is for round stock.

Thinking a torque wrench simply turns fasteners. It measures tightness.

Assuming 12-point grips better than six-point. More positions, less grip.

Thinking Phillips cam-out is a defect. It was designed in.

Work one in under a minute

A wheel nut is seized. A technician has an adjustable wrench, a 12-point socket, a six-point socket, and a breaker bar. What should be used, and what should be avoided?

A six-point socket on the breaker bar.

Six-point over 12-point because the fastener is seized and about to be given a great deal of torque. Six broader contact faces are far less likely to round the corners off than twelve narrow ones.

A breaker bar over a ratchet because the ratchet's pawls are the weakest part of the assembly under a heavy first pull, and because the longer handle multiplies the effort - torque is force times distance from the center.

Avoid the adjustable wrench entirely. Its movable jaw flexes and grips only two flats, which on a seized fastener is how you turn a hexagon into a circle.

Once it is loose, the ratchet is the right tool for spinning it off, which is the division of labor the two tools exist for.

Where this leads

Every tool here is a lever applied to a rotation, which makes this the torque lesson in practical form, and the fasteners these turn are the next lesson.