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Grade 8 Hex Cap Screw, Plated

Selected J429 Grade 5 Hex Cap Screw PlatedHex Bolts and Cap Screws
J429 Grade 5 Hex Cap Screw PlatedHex Bolts and Cap Screws

SAE J429 Grade 8 hex head cap screws are common, high-strength fasteners manufactured from heat-treated medium carbon alloy steel, quenched and tempered. Grade 8 cap screws are available in diameters from 1/4" through 1 1/2" inclusive. Dimensional specifications are governed by ASME B18.2.1. Grade marking consists of 6 radial lines. Inch series fasteners meeting SAE J429 Grade 8 specifications are general use fasteners commonly used in automotive and construction related industries. These fasteners are available in yellow zinc plated finish. Zinc plating sacrifices itself, corroding before the base material, offering added corrosion resistance.

Products

Dimensional Specifications

Finished bolt and cap screw dimensions
Per ASME B18.2.1-2012

  Nominal Diameter  

 UNC UNF E F G H J LT Y
Body Diameter Width Across Flats Width Across Corners Head Height Wrench Height Thread Length Transition Length
Max Min    Basic    Max Min Max Min Basic Max Min Min Lengths up to 6" Lengths > 6" Max
1/4 0.25 20 28 0.25 0.2405    7/16 0.438 0.428 0.505 0.488    5/32 0.163 0.15 0.106 0.75 1 0.25
5/16 0.3125 18 24 0.3125 0.3065    1/2 0.5 0.489 0.577 0.557 13/64 0.211 0.195 0.14 0.875 1.125 0.275
3/8 0.375 16 24 0.375 0.369    9/16 0.562 0.551 0.65 0.628 15/64 0.243 0.226 0.16 1 1.25 0.312
7/16 0.4375 14 20 0.4375 0.4305    5/8 0.625 0.612 0.722 0.698    9/32 0.291 0.272 0.195 1.125 1.375 0.357
1/2 0.5 13 20 0.5 0.493    3/4 0.75 0.736 0.866 0.84    5/16 0.323 0.302 0.215 1.25 1.5 0.385
9/16 0.5625 12 18 0.5625 0.5545 13/16 0.812 0.798 0.938 0.91 23/64 0.371 0.348 0.25 1.375 1.625 0.417
5/8 0.625 11 18 0.625 0.617 15/16 0.938 0.922 1.083 1.051 25/64 0.403 0.378 0.269 1.5 1.75 0.455
3/4 0.75 10 16 0.75 0.741 1 1/8 1.125 1.1 1.299 1.254 15/32 0.483 0.455 0.324 1.75 2 0.5
7/8 0.875 9 14 0.875 0.866 1 5/16 1.312 1.285 1.516 1.465 35/64 0.563 0.531 0.378 2 2.25 0.556
1 1 8 14 1 0.99 1 1/2 1.5 1.469 1.732 1.675 39/64 0.627 0.591 0.416 2.25 2.5 0.625
1 1/8 1.125 7 12 1.125 1.114 1 11/16 1.688 1.631 1.949 1.859 11/16 0.718 0.658 0.461 2.5 2.75 0.714
1 1/4 1.25 7 12 1.25 1.239 1 7/8 1.875 1.812 2.165 2.066 25/32 0.813 0.749 0.53 2.75 3 0.714
1 3/8 1.375 6 12 1.375 1.363

2 1/16

 2.062 1.994 2.382 2.273 27/32 0.878 0.81 0.569 3 3.25 0.833
1 1/2 1.5 6 12 1.5 1.488 2 1/4 2.25 2.175 2.598 2.48 15/16 0.974 0.902 0.64 3.25 3.5 0.833
  1. All dimensions are in inches.
  2. Usable thread length for Hex Head Cap Screws under 6 1/4" long can be approximated by the equation THREAD LENGTH = (2 X DIAMETER) + 1/4″

Mechanical Properties

Medium Carbon Steel, Heat Treated, Quenched and Tempered Per SAE J429 2014-05
Diameter Full Size Proof Load Yield Strength Tensile Strength Elongation Reduction in Area Core Hardness
psi Min psi Min psi Min % Min % Rockwell
1/4 thru 1 1/2" 120,000 130,000 150,000 12 35 C33 to C39

Governing Standards

SAE J429 Covers the mechanical and material requirements for inch series fasteners used in automotive and related industries in diameters through 1-1/2″.
ASME B18.2.1 Covers the complete general and dimensional data for multiple types of inch series square and hex bolts and screws.
ASME B1.1 UNC & UNF Class 2A Specifies the thread form, series, class, allowance, tolerance, and designation for unified screw threads.

Grade 8 Head Marking
Grade 8 Material Marking

Chemical Properties

Per SAE J429 2014-05
Grade Material Carbon Phosphorus Sulfur Boron Tempering Temperature
% by weight % by weight % by weight % by weight Min
8 Carbon (1) Steel with additives (e.g. Boron (2) or Cr, or Mn) 0.25-0.55 0.025 max 0.025 max (5) 0.003 800F
Medium Carbon Steel 0.25-0.55 0.025 max 0.025 max (5)   800F
Alloy Steel (3,4) 0.25-0.55 0.025 max (6) 0.025 max (6)   800F
  1. 1. For steels of these types there shall be sufficient hardenability to ensure a microsructure consisting of approximately 90% martensite (refer Table 3) in the core of threaded sections of the fasteners after hardening and quenching and before tempering.
  2. 2. When boron is added the limits shall be 0.0005 % to 0.003 %.
  3. 3. Alloy steel shall contain at least one of the following elements in the minimum quantity given: chromium 0.30 %, nickel 0.30 %, molybdenum 0.20 %, vanadium 0.10 %, manganese 1.65%. Where elements are specified in combinations of two, three, four, or five and have alloy contents less than those given above, the limit value to be applied for steel class determination is 70 % of the sum of the individual limit values shown above for the two, three, four or five elements concerned.
  4. 4. For steels of these types there shall be sufficient hardenability to ensure a microsructure consisting of approximately 90% martensite (refer Table 3) in the core of threaded sections of the fasteners after hardening and quenching and before tempering.
  5. 5. For studs only, sulfur content may be 0.13% maximum.
  6. 6. Alloy steel used to make fasteners by hot forging or machining may have a maximum content by weight of 0.030% P (phosphorus) and 0.040% S (sulfur).