FASTENERS 101™
Bolt FAQ

What are Bolts?

Bolts are fasteners engineered to be used with nuts to hold materials together.

What are bolts for wood called?

There are many varieties of bolts for wood. Carriage bolts and lag bolts are engineered for use with wood.

Where can I buy bolts?

You can shop Bolts right here.

How do bolt measurements work?

The standard bolt measurement includes the thread diameter, thread pitch, and length.

What is bolt pre-load?

Bolt-preload refers to tightening a bolt before weight or stress is added to the assembly. Bolt pre-load ensures that the bolt will not absorb all of the load, and that it will be spread evenly through the materials.

How does bolt pretension work?

Tightening a bolt against two objects before adding weight to the material allows the bolt to disperse the weight.

How do bolt extractors work?

Bolt removal tools use left hand drilling to extract in two steps. Step one, drill into the bolt head to gain create a pilot hole for the extractor. Step two, insert the extractor bit that spins the reverse direction of the threading to spin the bolt loose.

How is bolt length measured?

Bolts with flat heads are measured from the top of the head to the bottom of the thread. All other bolts are measured from the bottom of the head to the end of the thread. Bolt length is always measured from under the head to the tip except on flat head varieties where they are measured from the top of the head to the tip.

What is a bolt without a head called?

Bolts without heads are called Set Screws or Grub Screws.

What type of bolt do I need?

The type of bolt you need will depend on the items you are connecting (ex. Materials, size, diameter, environment).

What do the numbers on bolts mean?

The numbers and letters on a bolt may be the manufacturer markings and/or the grade of the material.

What is a carriage bolt?

A carriage bolt, also known as a coach bolt, is a large, strong bolt, with an unthreaded square under the head used in wood.

What three measurements determine the size of a bolt?

The diameter, thread pitch and length determine the size of a bolt

What is a lag bolt?

A lag bolt is a large, partially threaded screw, typically with a hex head, that has excellent retention in wood.

How do I use anchor bolts?

An anchor bolt must be inserted into a pre-drilled hole with a hammer and then tightened against an object. This will cause the anchor to expand and lock in place.

How do I use lag bolts?

A lag bolt is installed by drilling a hole into wood and then driving the screw in with a socket or wrench.

For more detailed information please visit our Fasteners 101 Resource Pages

Have a question but don't see the answer? Send us an email on our Contact Us page.