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Bolt, Screw, Nut and Washer Identification Chart

At one time or another, all of us (even the pros) misidentify a fastener.  Not that the guys at the hardware store don't need a chuckle every now and them.  Use this handy chart, courtesy BoltDepot.com, to get the name right the first time!

Fastener Categories






Wood Screws
Screws with a smooth shank and tapered point for use in wood.
Abbreviated WS
Machine Screws
Screws with threads for use with a nut or tapped hole.
Abbreviated MS
Thread Cutting Machine Screws
Machine screws with a thread cutting (self tapping) point.
Sheet Metal Screws
Fully threaded screws with a point for use in sheet metal.
Abbreviated SMS


Self Drilling SMS
A Sheet metal screw with a self drilling point.
Hex Bolts
Bolts with a hexagonal head with threads for use with a nut or tapped hole.
Abbreviated HHMB or HXBT
Carriage Bolts
Bolts with a smooth rounded head that has a small square section underneath.
Lag Bolts
Bolts with a wood thread
and pointed tip.
Abbreviated Lag





Flange Bolts
Flange bolts have a flange on the bottom of the head that distributes the load like a washer.
Socket Screws
Socket screws, also known as Allen head, are fastened with a hex Allen wrench.
Eye Bolts
A bolt with a circular ring on the head end. Used for attaching rope or chain.
Eye Lags
Similar to an eye bolt but with wood threads instead of machine thread.
U-Bolts
Bolts in U shape for attaching to pipe or other round surfaces. Also available with a square bend.
J-Bolts
J shaped bolts are used for tie-downs or as an open eye bolt.
Shoulder Bolts
Shoulder bolts (also known as stripper bolts) are used to create a pivot point.
Elevator Bolts
Elevator bolts are often used in conveyor systems. They have a large, flat head.
Sex Bolts
Sex bolts (a.k.a. barrel nuts or Chicago bolts) have a female thread and are used for through bolting applications where a head is desired on both sides of the joint.
Mating Screws
Mating screws have a shoulder that matches the diameter of the sex bolts they are used with.
Hanger Bolts
Hanger bolts have wood thread on one end and machine thread on the other end.
Set Screws
Machine screws with no head for screwing all the way into threaded holes.

Head Styles

Flat
A countersunk head with a flat top.
Abbreviated FH
Oval
A countersunk head with a rounded top.
Abbreviated OH or OV
Pan
A slightly rounded head with short vertical sides.
Abbreviated PN
Truss
An extra wide head with a rounded top.
Round
A domed head.
Abbreviated RH
Hex
A hexagonal Head.
Abbreviated HH or HX
Hex Washer
A hex head with built
in washer.
Slotted Hex Washer
A hex head with built in washer and a slot.
   
Socket Cap
A small cylindrical head using a socket drive.
Button
A low profile rounded head using a socket drive.
   

Drive Types

Phillips
The standard drive type for most screws.
Abbreviated PH
Frearson
Similar to Phillips. Requires a Frearson driver for installation.
Slotted
A slot in the head.
Abbreviated SL
Combination
A combination of slotted and Phillips drives.
Abbreviated Combo
Socket, Hex or Allen
A hexagonal hole for use with an Allen wrench.
One Way
Installs with a normal slotted driver but can not be removed without special tools.
Square
Also known as Robertson drive.
Abbreviated SQ or SD.
Star
Also known as Torx®. A six-pointed star pattern, specifically designed to prevent cam-out and stripped heads.

Nut Types

Hex
A six sided nut. Also referred to as a finished hex nut.
Nylon Insert Lock
A nut with a nylon insert
to prevent backing off.
Also referred to as a Nylock
Jam
A hex nut with a reduced height.
Nylon Insert Jam Lock
A nylock nut with a reduced height.
Wing
A nut with 'wings' for hand tightening.
Cap
A nut with a domed top over the end of the fastener.
Acorn
Acorn nuts are a high crown type of cap nut, used for appearance.
Flange
A nut with a built in washer like flange.
Tee
A nut designed to be driven into wood to create a threaded hole.
Square
A four sided nut.
Prevailing torque lock
A non-reversible lock nut used for high temperature applications
K-Lock or Kep
A nut with an attached free-spinning external tooth lockwasher.
2-Way Reversible Lock
A lock nut that can be installed either side up. Often used in high temperature applications.
Coupling
Coupling nuts are long nuts used to connect pieces of threaded rod or other male threaded fasteners.
Slotted
Slotted nuts are used in conjunction with a cotter pin on drilled shank fasteners to prevent loosening.
Castle
Castle nuts are similar to slotted nuts but with the slots in a rounded section above the main nut.

Washer Types

Flat
A flat washer used to
distribute load. Available in SAE, USS, and other patterns.
Fender
An oversize flat washer used to further distribute load especially on soft materials.
Finishing
A washer used to obtain a 'finished' look. Usually used with oval head screws.
Split Lock
The most common style of washer used to prevent nuts and bolts from backing out.
External Tooth Lock
A washer with external 'teeth' Used to prevent nuts and bolts from backing out.
Internal Tooth Lock
A washer with internal 'teeth' Used to prevent nuts and bolts from backing out.
Square
A square shaped washer.
Dock
Dock washers have a larger outside diameter and are thicker than standard.
   
Ogee
Thick, large diameter, cast iron washers with a curved or sculpted appearance. Typically used in dock and wood construction
Sealing
A neoprene washer bonded to a metal backing. Used to seal out air/water or dampen noise and vibration.
   

About the author: BoltDepot is an internet fastener retailer in the tradition of the old hardware store, maintaining its family-owned atmosphere and commitment to service while offering our complete catalog of fasteners online!

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