Fastener Abbreviations

18-8
Stainless Steel with 18% Chrome and 8% Nickel

2, 5 or 8
Strength grade of screw or nut

2A (3A)
Class of Thread Fit for inch screws

2B (3B)
Class of Thread fit for inch nuts

2H
Nut strength level designation (ASTM A194 Grade 2H Heavy Hex Nut)

6g
Class of thread fit for metric screws

6H
Class of thread fit for metric nuts

A325
Heavy Hex Structural Bolt (ASTM A325), similar to Grade 5

A490
Heavy Hex Structural Bolt (ASTM A490), similar to Grade 8

A574
Strength grade for Socket head cap screws (ASTM A574)

AISI
American Iron and Steel Institute, specifies chemical composition of steels

ANSI
American National Standards Institute

AS
Alloy Steel

ASME
American Society of Mechanical Engineers

ASTM
American Society for Testing and Materials

B
When followed by a number (ex B-90) hardness measured on the Rockwell B Scale or an abbreviation for Boron

Bake (Bake-Out)
Heat Treat process used in plating to prevent Hydrogen Embrittlement

Bevel
Style of washer (square with a taper) used with I beams

Belleville
Style of lock washer, also called conical spring washer

BHCS
Button Head Cap Screw

BHN
Hardness measured with a Brinell Hardness Tester

BS
British Standard

C
When followed by a number (ex C-35) hardness measured on the Rockwell C Scale or an abbreviation for Carbon

CH
Case hardened (type of heat treatment)

C/R
Cross Recess Drive (typically Phillips style) or Chamfer/Radius

Cad
Cadmium Plating

Cad/Wax
Cadmium Plating with a topcoat of Wax

COO
Country of Origin

CRES
Corrosion resistant steel (usually refer to 18-8 or 316 stainless steel)

CS (cs)
Carbon Steel or Countersunk

DAC (Dac 320)
Dacromet Coating (Registered Trademark of Coatings International)

D/C Nut
Double Chamfered Nut (distinguish from washer faced)

D/E
Double Ended Stud

DIN
German Standards Organization

Deltaseal
Magnigard coating (registered trademark of Magni Engineered Coatings)

Dorrltech
Magnigard coating (registered trademark of Magni Engineered Coatings)

Driseal
Pipe Thread (registered trademark of Parker Hannifin)

ET
External Thread

FB
Flange Bolt

F436
Hardened flat washer with dimensions per ASTM F436

FHCS
Flat Head Cap Screw

FIM
Full Indicator Measurement

Flng
Hex Flange Bolt or Nut

FW
Flat Washer

galv
Galvanized, typically refers to Hot Dip Galvanized

Gr
Grade, refers to strength level of screw or nut (ex: Grade 2, Grade 5 or Grade 8)

Hardened
A product that has been heat treated

HB
Hex bolt or Hardness reading measured on the Brinell Scale

H.T.
Heat Treated

HCS
Hex Cap Screw or High Carbon Steel

H.D.G.
Hot Dip Galvanized

Hex Bolt
Can refer to either a "bolt" or a "cap screw"

HHCS
Hex Head Cap Screw (also an abbreviation for Heavy Hex Cap Screw)

HRB
Hardness measured on the Rockwell B scale

HRC
Hardness measured on the Rockwell C scale

HWH
Hex Washer Head

ID
Identification (usually refers to manufacturer logo)

IFI
Industrial Fastener Institute

IH
Indented Head

in.
Inch

ISO
International Standards Organization

ISIR
Initial Sample Inspection Report

IT
Internal Thread

J429
SAE standard that specifies strength levels of screws

J995
SAE standard that specifies strength levels of nuts

k
Short hand for the number 1,000

Keps
Nut with a permanently attached washer

Kips
1,000 pounds

ksi
Thousand of pounds per square inch

lb (lbs)
Pounds

Lb
Body Length on screws

LCS
Low Carbon Steel

Lg
Grip Length (distance from head to full threads) on screws

LH
Left Hand Thread

L/W
Lock Washer

M
Metric or short hand for the number 1,000

Magnigard
Magni Coating (Registered Trademark of Magni Engineered Coatings)

Mfg
Manufacturer

mm
Millimeter

MS
Machine screw

MTR
Material Test Report

#3 (or #7)
Refers to head design of a plow bolt

NC
Unified National Coarse Thread

NE (NU, NTE, NTU)
Designations that define the thickness of Nylon Insert Lock Nuts

NF
Unified National Fine Thread

Nom
Nominal (reference dimension)

NPT
National Tapered Pipe Thread

p
Thread Pitch

P/B
Plow Bolt

Ph Dr
Phillips Drive (cross recess)

Pl
Plain finish

P/N
Part number

Phos (P & O)
Phosphate and Oil Coating (typically Zinc Phosphate and Oil)

Pozi Drive
Special cross recess (registered trademark of Camcar Textron)

PPAP
Production Part Approval Process

psi
Pounds per square inch

PZ
Pozi-Drive style of cross recess

R
Radius

Rb (RB or HRB)
Hardness measured on the Rockwell "B" scale

Rc (RC or HRC)
Hardness measured on the Rockwell "C" scale

RT
Rolled Threads

SAE
Society of Automotive Engineers. When used with washers it means "small OD"; when used with screws or nuts it means fine thread

Screw
Can refer to any type of externally threaded fastener but typically a sheet metal screw

Sems
Screw with a permanently attached washer

Serrated
Locking serrations on bearing face of screw or nut

SHCS
Socket Head Cap Screw

Sl
Slotted Drive

SMS
Sheet Metal Screw

Sq
Square, can refer to square head bolt or square nut

SS or S/S
Stainless Steel

St
Steel

Taptite
Special triangular thread forming screw (registered trademark of Reminc)

T.H.
Through Hardened (type of heat treatment)

TIR
Total Indicator Reading

T/S
Tapping Screw

Torx
6 Lobe Drive (Torx Drive, registered trademark of Camcar Textron)

TPI
Threads per Inch

TT (TR)
Taptite thread (registered trademark of Reminc), also called Tri-Roundular

TTH
Threaded to Head

Type 1 (23, 25)
Special thread forming or cutting tapping screws

Type AB (F, T)
Special thread forming or cutting tapping screws

UNC
Unified National Coarse Thread

UNRC
Unified National Coarse Thread with Radius Root (standard rolled thread form)

UNF
Unified National Fine Thread

UNRF
Unified National Fine Thread with Radius Root (standard rolled thread form)

UNJ
Unified National Thread with Large Radius Root (special fatigue resistant thread)

UNR
Unified National Thread with radius root

USS
United States Standard. When used with washers it is for large OD; when used with screws or nuts it means coarse thread

UTS
Ultimate Tensile Strength

WAC
Width Across Corners

WAF
Width Across Flats

W/F
Washer Faced (can refer to a Nut or Cap Screw)

Whitworth
British Thread Standard (not the same as UN threads)

Y
Yellow Chromate

YS
Yield Strength

Zn
Zinc, usually referencing zinc plating (assumed to be zinc with clear chromate)

Zn/C (ZC)
Zinc Plating with Clear Chromate topcoat

Zn Phos
Zinc Phosphate and Oil (same as Phos and Oil)

Zn/Wax
Zinc Plating with a topcoat of wax

Zn/Y (ZY)
Zinc Plating with Yellow Chromate topcoat