COMMON ABBREVIATIONS USED WITH FASTENERS
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 Computer Aided Design/Drafting
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 screw or nuts 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