Thread engagement length decides whether a bolt fails predictably in tension or the threads strip out. Here is how to size it for steel, aluminum, and other soft materials, with a worked example.
Torque sets bolt preload through friction. Learn the T = K D F equation, how to choose the nut factor K, and a worked example on a Grade 8 bolt.
Metric Hex Bolt Head Dimensions When working with metric fasteners, the wrench size (width across flats) follows a different pattern than US bolts. Here’s the quick reference: Bolt Size Width Across Flats (mm) Width Across Corners (mm) Head Height (mm) M5 8 9.24 3.5 M6 10 11.55 4.0 M8 13 15.01 5.3 M10 16 (or … Read more
Matching Nut Grades to Bolt Grades Using the wrong nut with a high-strength bolt is a surprisingly common mistake — and it’s dangerous. A Grade 5 nut on a Grade 8 bolt will strip the nut threads before the bolt reaches its rated clamp load. Always match (or exceed) the nut grade to the bolt … Read more
How to Identify a Hex Bolt’s Grade Every hex bolt has markings on its head that tell you its material grade and mechanical properties. Those radial lines, numbers, and letters aren’t decorative — they’re a specification. Knowing how to read them means you can verify the right bolt is in the right application without pulling … Read more
Standard Flat Washer Sizes Flat washers distribute load under a bolt head or nut, protect the surface from damage, and span oversized or slotted holes. The two common types in the US are: Type A (Narrow) — general purpose, standard series Type B (Wide) — larger OD for better load distribution on soft materials Dimensions … Read more
Standard Hex Nut Sizes These are the basic dimensions for standard hex nuts per ASME B18.2.2. The “width across flats” is what you need for wrench/socket sizing. Nominal Size Threads/in (UNC) Width Across Flats (in) Width Across Corners (in) Height (in) 1/4″ 20 7/16 0.505 7/32 5/16″ 18 1/2 0.577 17/64 3/8″ 16 9/16 0.650 … Read more
Standard Hex Cap Screw Dimensions Hex cap screws (also called hex cap bolts or hex head bolts) are the workhorse fastener of mechanical assembly. This table covers dimensions per ASME B18.2.1 — the data you need for designing bolt holes, counterbores, clearances, and grip lengths. Key Dimensions Explained Width across flats (F) — your wrench/socket … Read more
Metric Tap & Clearance Drill Sizes This table covers standard coarse pitch metric threads (the default — if a drawing says “M10” without specifying pitch, it means M10×1.5 coarse). For each thread size, you get the tap drill (for cutting internal threads) and clearance drill (for a bolt to pass through freely). Thread Pitch (mm) … Read more
UNF Thread Specifications UNF (Unified National Fine) threads per ASME B1.1. Fine threads have a larger minor diameter than coarse threads of the same nominal size, which means higher tensile strength and better performance in thin-walled parts. Size TPI Major Ø (in) Pitch Ø (in) Minor Ø (in) Tensile Stress Area (in²) #0-80 80 0.0600 … Read more