Common Fastener Related Abbreviations



Abbreviation Definition
#3 (or #7) Refers to head design of a plow bolt
&NT With nut
18-8 Stainless Steel with 18% Chrome and 8% Nickel
2, 5 or 8 Strength grade of a 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
AN Precedes a dimensional specification for aircraft fasteners developed by the Aeronautical Standards Group.
ANSI American National Standards Institute
AS Alloy steel
ASME American Society of Mechanical Engineers
ASTM Used before a standard number developed by the American Society for Testing and Materials group.

When followed by a number (ex: B-90), indicates hardness measured on the Rockwell B Scale.

Also 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
BR Brass
BS British Standard
BSF British Standard Fine
BSW British Standard Whitworth
BT Bolt (on drawings)

When followed by a number (ex: C-35), indicates hardness measured on the Rockwell C Scale.

Also an abbreviation for Carbon.

C/R Cross recess drive (typically Phillips style), Also Chamfer/Radius
Cad Cadmium plating
CAD Computer Aided Design / Drafting
Cad/Wax Cadmium plating with a topcoat of wax
CH Case hardened (type of heat treatment)
CL Class (Metric material/Strength specification)
COO Country of Origin
CR Chrome
CRES Corrosion resistant steel (usually refer to 18-8 or 316 stainless steel)
CS (cs) Carbon or Steel, Also Countersunk
CSS Counter sunk screw (flat or oval head)
CT Course Thread
DAC (Dac 320) Dacromet coating (registered trademark of Coatings International)
D/C Nut Double chambered nut (distinguished from washer faced)
 D/E Double ended stud 
 DIN An abbreviation for Deutsches für Normung, the German standards body.  In reference to fasteners, DIN indicates fasteners that conform to a specific metric standard (will be followed by the standard number). 
 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)
External thread 
F Fully threaded
FB Flange Bolt
F436 Hardened flat washer with dimensions per ASTM F436
FH Flat head
FHCS Flat head cap screw
FIL Fillister Head
FIM Full indicator measurement
FIN Finishing (washer)
Flng Hex flange bolt or nut
FNDR Fender (washer)
 FT Fine thread or Fully threaded 
 FW Flat washer 
 G Grade 
galv  Galvanized, typically refers to Hot Dip Galvanized 
Gr Grade, refers to strength level of screw or nut (ex: Grade 2, Grade 8)
GV Galvanized
HB Hex bolt, Also hardness reading measured on the Brinell Scale
HCS Hex cap screw, also high Carbon steel
HD Head
H.D.G. Hot dip galvanized
HHCS Hex head cap screw, Also heavy hex cap screw
HHMB Hex head machine bolt
HRB Hardness measured on the Rockwell B scale
HRC Hardness measured on the Rockwell C scale
H.T. Heat treated
HWH Hex washer head
HX Hex
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
JMNT Jam Nut
K Shorthand for the number 1,000
Keps Nut with a permanently attached washer
Kips 1,000 points
ksi Thousands of pounds per square inch
LB (lb) Lag bolt, Also weight in pounds
Lb Body length on screws
LCS Low Carbon steel
LH Left hand thread
LW Lock washer
M Metric
MB Machine bolt
Mfg Manufacturer
mm Millimeter
MS Machine Screw
MSNT Machine Screw Nut
MTR Material Test Report
 NC Unified National Course 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 
 NT Nut
 OH Oval head 
OV  Oval head 
Thread pitch, Also Phillips head
P/B Plow bolt
PH Phillips head
Phil. Or Ph Dr Phillips drive
Phos (P & O) Phosphate and oil coating (typically Zinc Phosphate and Oil)
Pl Plain finish
P/N Part number
PN Pan head
Pozi Drive Special cross recess (registered trademark of Camcar Textron)
PPAP Production part approval process
psi Pounds per square inch
PT Partial thread
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
RD Round head
RH Round head, or Right hand thread
RT Rolled threads
 S Slotted
S/S  Stainless steel 

Standard American Equivalent - Uses inches as unit of measure, as opposed to metric.   

Also: SAE Pattern (washers). These washers have a smaller inside diameter than USS pattern washers.

Also: Society of Automotive Engineers

Also: When used with washers, it means "small OD."

Also: When used with screws or nuts, it means "fine thread."

SBR Silicon bronze
Square drive 
SEMS A type of pre-made screw and washer assembly 
SHCS Socket head cap screw
SKT Socket
SL Slotted
Slot. Slotted drive
SMS Sheet metal screw
Sq. Square. Can also refer to square head bolt or square nut.
SS Stainless steel or Set Screw
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
UNF Unified National Fine Thread
UNR Unified National Thread with radius root
UNRC Unified National Coarse Thread with Radius Root (standard rolled thread form)
UNRF Unified National Fine Thread with Radius Root (standard rolled thread form)

USS Pattern (washers).  These washers have a larger outside diameter than SAE pattern washers. 

Also used to indicate US course thread.

UTS Ultimate tensile strength
WAC Width across corners
WAF Width across flats
W/F Washer faced (can refer to a nut or a cap screw)
Whitworth British Thread Standard (not the same as UN threads)
WS Wood screw
Y Yellow chromate
YS Yield Strength
Zn Zinc, usually referencing zinc plating (assumed to be clear 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