Is It a Bolt or a Screw? Fastener Slang

By Marketing October 08, 2021

It is true that, to the naked eye, there does not appear to be much difference between a bolt and a screw. They are both threaded fixings and have a head for tightening the fastener but there is more to it than that.  The first time I was asked if we had a whiz nut, I was picturing something totally different.

             Hex Cap Screw                                    Hex Bolt

   hex bolt or hex cap screw       

A hex cap screw has tighter tolerances on the body dimensions and features a chamfered end and a washer face under the bolt head. A hex cap screw is often called a finished hex bolt. Hex bolts have a flat end and lack the washer face under the head.


RBH Part Name


½ Nut

Jam Nut

A thinner pattern of nut, sometimes used as a second nut to 'jam' another nut in place preventing loosening.

½ Moon Key

Woodruff Key

Used to connect a rotating machine element to a shaft.  The key prevents relative rotation between the two parts and enables torque transmission

Allen Head Bolt

Socket Cap Screw

Refers to a hex head cap screw. This is a hex bolt with a circular washer face under the head. This does not extend past the edge of the hex as a flange bolt would.

In most cases there is no operational difference between a hex head cap screw (left) and a hex bolt (right).

Hex caps should not be confused with socket caps.

Allen Wrench

Hex Key

A hex key or Allen key is a simple tool used to drive bolts and screws with hexagonal sockets in their heads.

Automation Nut or Stover Lock Nut or Top Lock Nut

All Metal Locknut

All-metal lock nuts are often used in cases where nylon insert lock nuts may not be practical to use, such as in high heat applications.


Hex Cap Screw

Bolts with a hexagon shaped head and machine threads for use with a nut or in a tapped hole.

Butterfly Nut

Forged Wing Nut

A nut with 'wings' for easy manual assembly.

Cap Nut

Acorn Nut

A nut with a slightly pointed domed top that covers the end of a bolt. Acorn nuts are sometimes confused with cap nuts which are domed but lack a point.

Case Locking Bolts

Serrated Screw

These screws have a flange that's at least 10% larger than a standard flange for more gripping power. The flange distributes pressure where the screw meets the surface, eliminating the need for a separate washer. Serrations under the head grip the material surface for mild vibration resistance.

Castle Nut

Slotted Hex Nut

Slotted nuts have grooved heads that align with holes in the mated bolt to accept the insertion of a cotter pin, locking the nut in place. They are commonly used to ensure that shaft components in certain automotive assemblies do not separate or to maintain machine settings in manufacturing environments.

Connector Nut

Rod Coupling Nut

Coupling nuts are internally threaded fasteners that join threaded rods, pipes, and other threaded parts, sometimes parts of differing sizes.

Countersunk bolt

Flat Head

Used when a smooth surface is required. Common applications include bridge decking, walkways, and railing.


Nylon Insert Locknut

A locknut with a nylon collar that increases friction on the screw thread.


Recoil Insert

Wire inserts enable you to produce strong, permanent threads in metals and plastics and strong threads in softer metals.

Lag Bolt

Hex Lag Screw

Large wood screws with hexagon shaped head.

Plaster Washer

Fender Washer

A flat washer that was originally developed for automotive repair.  They are presently used more in applications where extra-wide bearing surface is required for installation.

Pop Rivet

Blind Rivet

A non-removable fastener

Red Brass

Silicone Bronze

A low-lead brass alloy that is generally composed of 96 percent copper with superior corrosion resistance.

Roll Pin or Split or Spring Pin

Tension Pin

Expand and create tension against the walls of holes. When inserted through two or more objects, they fix the relative positions of these objects. These stress distributing pins are used as dowels, spacers, and cotter pins along with a multitude of other applications.

Shake Proof Washer

Lock Washer

special type of washer that's designed to create tension so that the bolt doesn't loosen or otherwise come out of its installed position. Lock washers aren't flat. Lock washers work by preventing the rotational movement of the installed bolt.

Sheet Metal Screw

Tapping Screw

a self-tapping screw (or sheet metal screw), is designated as such because it contains form mating threads (thereby “tapping” the threads) in a pre-drilled hole into which they are driven.

Stove Bolt

Machine Screw

Used for binding material together by going into a tapped hole or through a hole and being held by a nut. Machine screws are meant to apply two metal work pieces together, with the use of a threaded pre-tapped hole or through a hole and held with a nut.

Stripper Bolt

Shoulder Screw

Bolt with an unthreaded shoulder that is larger diameter than the threads.

TEK Screw

Self-Drilling Screw

Tek screws are self-drilling screws that can help you tackle fastening jobs quickly. Commonly used in the electrical and roofing industries, these screws feature drill bit tips that eliminate the need to drill a separate pilot hole before inserting the screw.

Whiz Nut

Serrated Flange Nut

Flange nuts have a washer-like base to distribute pressure over a greater surface area and ensure the fastener stay tight. They are commonly used in manufacturing assembly lines where operations are speeded by using a single fastener instead of a nut and washer.

Royal Brass and Hose has been selling fasteners (nuts and bolts) since we purchased Cornette Fasteners in Maryville, TN in the late 1980s. In 2019, we purchased Hardline Industrial Fasteners in Birmingham, AL. Currently, we stock over 16,000 different fasteners.

See our separate blog for our Fastener part number system.

Need help?

Contact your Royal Brass and Hose local sales representative or call 800-669-9650 to speak with a member of our Customer Service team at any of our locations (Knoxville, TN; Marietta, GA; Orlando, FL; Charlotte, NC; Little Rock, AR; Fort Worth, TX; Benton, IL; Madisonville, KY; Princeton, WV; Birmingham, AL; Calvert City, KY)