Fasteners

Mr. Lombardi

Fasteners

There are many different types of fasteners. Screws, Nuts, Bolts, etc.

Each one performs specific task best accomplished by that specific fastener.

Screws

A headed threaded fastener that is designed to be used by forming its own threads.

Bolts

A bolt is the term used for a headed fastener having external threads that meet an exacting, uniform bolt thread specification

Nuts

A nut is a type of hardware fastener with a threaded hole.

Along with a bolt, nuts are designed to capture and fasten objects together.

Cotter Pin

A metal fastener with two tines that are bent during installation, similar to a staple or rivet

Retaining Ring

A small circular steel ring, often resembling the letter "C," that is usually inserted into a slot in a pivot pin to hold the pin in a specified position.

Wing Nuts / Thumb Screws

A nut that can be tightened or removed without tools by turning it with fingers

Classification

There are 7 descriptors for every bolt. Material Diameter Pitch/Thread Head Shape Finish Class Grade

Material

Steel Stainless Steel Brass Etc.

Diameter

T – Thread Diameter R – Root Diameter (minor) S – Shank Diameter

Thread / Pitch

Measured in TPI (threads per inch)

Pitch

Thread Pitch is measured with a special gauge

Correct Pitch Gauge

Incorrect Pitch Gauge

Class

Class 1 = Loose Class 2 = Free Class 3 = Medium Class 4 = Close

Most are class 2. 3 is for precision assembly, and 4 is used for things like lathe lead screws and measuring instruments.

Head Shape

Many, many shapes and sizes

Hardware Grade

The grade tells the strength of the fastener.

Nuts and Bolts must be the SAME grade.

Grades (US)

Grade 2 – 74,000psi Grade 5 – 120,000psi Grade 8 – 150,000psi

Grade 2

Zinc plated low carbon steel. Best for general hardware use where high strength is not required.

Grade 5

Made from medium carbon steel, tempered and zinc plated. Best for automotive use and other areas where higher strength is desired.

Grade 8

Made from medium carbon alloy steel, tempered, and zinc plated. Best suited for applications where high strength and hardness is required.

Grades (Metric)

Grade 8.8 Grade 10.9

Grade8.8

Made from medium carbon steel and zinc plated. Best for general hardware use where high strength is not required. Standard metric thread pitches.

Grade 10.9

Made from alloy steel quenched, tempered, and zinc plated. Best for automotive use and other areas where high strength is needed.

Bolt Identification

Metric Bolt Identification

Common Nuts

L to R: Wing, hex, hex flange, and flanged weld (for stud welding) nuts.

More Common Nuts

L to R: Slotted, square, T, cap (or acorn), nylon locking, and castellated nuts

Washers

Four Common Types Flat Split Toothed Insulating

Common Washers

Torque To Yield Bolts (TTY)

They are tightened (torqued) until they just begin to stretch

This provides a very consistent clamping load and helps keep an even sealing pressure for the items being fastened

Torque to Yield bolts require special procedures

Tighten to the specified torque

Continue to turn the fastener just enough to cause it to begin to stretch

This will be specified in degrees of rotation

Torque Angle Gauge

Torque to Yield Graph

The End