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/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