How to Install Carriage Bolts

Written by c.l. rease
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How to Install Carriage Bolts
Carriage bolts eliminate the need for two wrenches to tighten a connection. (Monty Rakusen/Digital Vision/Getty Images)

The design of carriage bolts allows you to install the fastener without a helping hand. Below the half-round head of a carriage bolt sits a squared shoulder. When you drill a hole through material sized for the bolt, the head of the bolt will remain in place while you tighten the fastener onto the material. Using a hole too large for the bolt will result in the bolt head spinning in the material. This will not allow the carriage bolt to tighten in the material.

Skill level:
Moderately Easy

Things you need

  • Carriage bolt
  • Tape measure
  • Drill bit
  • Variable speed drill
  • Cutting fluid
  • Hammer
  • Washer
  • Nut
  • Adjustable wrench

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  1. 1

    Measure one side of a carriage bolt with a tape measure.

  2. 2

    Secure a drill bit matching the measurement of the carriage bolt into the chuck of a variable speed drill. Coat the drill bit with cutting fluid if you are drilling a hole into metal.

  3. 3

    Drill a hole through the material with the secured drill bit. Pump the trigger of the drill bit to keep it spinning at a slower RPM when drilling through harder materials.

  4. 4

    Slide the threaded end of the carriage bolt into the drilled hole. Push the head of the bolt against the surface of the material. Tap the head of the carriage bolt to seat the bolt to the material.

  5. 5

    Push a washer onto the threaded end of the carriage bolt. Thread a nut onto the end of the bolt. Spin the nut clockwise to seat it against the washer.

  6. 6

    Tighten the nut with an adjustable wrench.

Tips and warnings

  • Wear eye protection to avoid eye injuries when drilling the hole for the carriage bolt.

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