FASTENERS

Fasteners Described by several factors:

Material Head style Type Diameter Length Thread count

FASTENERS

Material Describes what the fastener is made from Some common examples:

Stainless steel Steel Brass Special coatings may also be added, such as zinc, in

order to prevent corrosion or enhance appearance

FASTENERS

Head style Describes the type of head on the fastener Selected depending upon the purpose of the

fastener Common head styles:• Flat• Oval• Pan• Truss• Round• Hex

FASTENERS

Type Designates the purpose of the fastener Some common types:• Wood screw• Machine screw• Sheet metal screw• Self drilling or self tapping• Hex bolt• Carriage bolt• Lag bolt• Set screw

FASTENERS

Diameter is expressed in inches with the exception of small screws

Expressed as a size number preceded by the # sign (i.e. #12)

Differing size numbers correspond with fractional measurements

A complete chart can be found in most handy reference guides

FASTENERS

Sample chart:

FASTENERS

Size Number Decimal Nearest Fractional

Measurement

#0 .060 1/16

#5 .125 1/8

#10 .190 3/16

#12 .216 7/32

Diameter is normally measured as shank diameter except in the case of tapered screws, such as wood screws, where the root is measured instead

Length is normally expressed in inches and is measured from where the material surface is assumed to be (the end of the fastener)

If the fastener head sits above the surface, the measurement is measured directly under the head of the fastener

FASTENERS

If the fastener is designed to be countersunk, the measurement is made from the point on the head where the surface of the material is

Thread count• Expressed as Threads Per Inch (TPI)• Simply means the number of threads per inch

measured along the length of the fastener• Used only with American fasteners• Only applies to machine threads• In general, smaller fasteners have finer threads,

therefore the thread count will be higher

FASTENERS

The relationship between a fastener size (diameter) and the number of threads per inch is standardized in a series

Two most common United States thread series: UNC (or NC) – Unified Course Thread (commonly

called course) UNF (or NF)– Unified Fine Thread (commonly called

fine) A complete table for these series can be found in

most handy reference guides

FASTENERS

Sample table:

FASTENERS

Fastener Size UNC (tpi) UNF (tpi)

#1 64 72

#10 24 32

¼” 20 28

3/8” 14 20

½” 12 20

¾” 10 16

1” 8 14

Bolt grade One final factor that should be considered when

dealing with bolts is grade Bolt grade is designated by numbers on the bolt

head The following are common grades of bolts:• Grade 2

SteelMost commonLeast expensive» Have no head markings

FASTENERS

Grade 5Case hardened steel (outside only is hardened)Not as strong as a fully hardened boltDesignated by three evenly spaced radial lines on the

head Grade 8

Fully hardened steelVery hard but somewhat brittleMore likely to snap off rather than bend under extreme

loadDesignated by 6 evenly spaced radial lines

FASTENERS

Alloy steelHigh strength steel alloyHeat treatedTypically not plated resulting in a dull black finishExtremely strong, but very brittle

It is important to have all physical factors (especially thread count) or the fastener will not fit properly

This also applies to any corresponding nut

FASTENERS

Metric fastenersDescribed similarly to American fasteners (material,

head style, type)Use thread pitch rather than thread count

Thread pitch Distance between threads Expressed in millimeters (measured along the length

of the fastener) Example: a thread pitch of 1.5 means that the

distance between one thread and the next is 1.5mm

FASTENERS

Different thread pitch designations similar to American fasteners: Standard Fine Extra or super fine

Nuts and washers Fasteners have numerous accessories to

accompany them and it is just as important to replace these items at the same time

FASTENERS

The following are common nuts and their uses:• Hex nut• Nylon insert lock nut

Has a nylon insert to prevent backing offAlso referred to as a Nylock

• Jam nutHex nut with reduced height

• Wing nutHas wings for hand tightening

• Cap or Acorn nutHas a domed top over the end of the fastener

FASTENERS

Flange nutA nut with a built in washer

Kep nutA nut with a built in external tooth lock washerUsed to speed up assembly

Square nutPrevailing torque lock nut

Non-reversableUsed for high-temperature applications

FASTENERS

The following are common washer types and their uses:• Flat

Used to distribute load• Fender

Oversized flat washerBetter distributes load especially on soft materials

• FinishingUsed for a finished appearanceUsed with oval head screws

• Split lockMost common styleUsed to prevent nuts and bolts from backing out

FASTENERS

External tooth lockUsed to prevent nuts and bolts from backing out

Internal tooth washerIdentical to above except teeth are inside

FASTENERS

FASTENERS

FASTENERS

FASTENERS

FASTENERS