Parts of a Bolt

A hex bolt holding two plates together, with its washer and nut.

Parts of a Bolt

Name Date

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1 2 3 4 5 6 7 8 9
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Write the name of each numbered part.Answer key

  1. Head
  2. Bearing surface
  3. Shank
  4. Thread
  5. Clamped parts
  6. Grip length
  7. Washer
  8. Nut
  9. Thread length

Drawn for this site by script, 2026-09-27. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

Next step Next: a screw and its thread

All 9 parts on the diagram

Show the list
  1. Head The wide end of the bolt, here a hexagon for a spanner. The bolt is tightened by turning the head or the nut.
  2. Bearing surface The flat underside of the head. It presses on the parts being held.
  3. Shank The smooth, unthreaded part of the bolt just below the head.
  4. Thread The spiral ridge the nut screws onto.
  5. Clamped parts The parts the bolt holds together. They are squeezed between the head and the nut.
  6. Grip length The thickness of the parts the bolt clamps together. It runs from under the head to the other side of the joint.
  7. Washer A thin plate with a hole. It spreads the nut's load over the part below it.
  8. Nut Screwed onto the thread and tightened against the washer. This clamps the joint.
  9. Thread length How far the thread runs along the bolt, from its end. The rest is the plain shank.

How this list was compiled: Read 2026-09-27. (1) NASA Reference Publication 1228, Fastener Design Manual (Richard T. Barrett, NASA Lewis Research Center, 1990), https://ntrs.nasa.gov/citations/19900009424 : bolts, nuts and washers; head styles; the bolt shank; thread lengths; grip length; the bearing surface under the nut; clamped parts and clamping load. (2) Wikipedia, Screw, https://en.wikipedia.org/wiki/Screw : the head, larger than the body, giving a bearing surface; the shank, fully or partially threaded; nuts and washers. Bolted joint, https://en.wikipedia.org/wiki/Bolted_joint : the bolt tensioned by turning the head or the nut, the clamped parts, grip length, thread length. Washer (hardware), https://en.wikipedia.org/wiki/Washer_(hardware) : a thin plate with a hole that distributes the load of a bolt or nut. Licence: own work

The drawing: Drawn for this site by script, 2026-09-27. Own work, nothing traced. Licence: own work

How it works

These are the parts of a bolt and the joint it makes: a hex bolt holding two plates together with a washer and a nut. The plates are cut through so the bolt shows in its hole.

Read the full guide

The bolt

The head's flat underside, the bearing surface, presses on the top plate. Below it the shank is plain, and the thread runs up from the end for the thread length.

The joint

The washer spreads the nut's load, and tightening the nut, or turning the head, squeezes the clamped parts together. Their thickness is the grip length, which tells you how long a bolt the joint needs.

  • For the thread's own parts, the pitch, crest, root and diameters, see the parts of a screw.

Questions and answers

What is the difference between a bolt and a screw?

The line is blurry. A fastener with a straight shank, made to take a nut or go into a tapped hole, is usually called a bolt. One with a tapered shank that forms its own thread as it is driven in is usually a screw.

What is the grip length of a bolt?

The thickness of the parts the bolt clamps together. It decides how long a bolt you need, and how much of the plain shank sits inside the joint.

What does a washer do?

It spreads the load of the nut or the bolt's head over a wider area of the part underneath.

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