bolt head types

7/31/2019 Bolt Head Types

http://slidepdf.com/reader/full/bolt-head-types 1/5

F-101 Screwdriver Tips and Fastener Sizes ARTISAN Hand Tools, Inc. Sheet 1

Document Number: F-101Description: Screwdriver Tips and Fastener Sizes

What is a Fastener?

A screw or bolt is a shaft with a helical groove or thread formed on its surface and hasprovisions at one end for turning. A screw or bolt consists of a cylindrical shaft, which inmany cases tapers to a point at one end, and with a helical ridge or thread formed on it,and a head at the other end which can be rotated by some means. Its main uses are tohold two or more objects together.

The thread is essentially an inclined plane wrapped around the shaft. The thread mateswith a complementary helix in the material. The material may be manufactured with themating helix using a tap, or the screw may create it when first driven in (a self-tappingscrew or wood screw). The head is specially shaped to allow a screwdriver or wrench torotate the screw, driving it in or removing it. The head is of larger diameter than the body of the screw and has no thread so that the screw cannot be driven deeper than the length of the shaft, and to provide compression.

Screws can normally be removed and reinserted without reducing their effectiveness. Theyhave greater holding power than nails and permit disassembly and reuse.

The vast majority of screws are tightened by clockwise rotation; this is commonly termed asa Right-hand thread. Screws with left-hand threads are used in exceptional cases, whenthe screw is subject to anticlockwise forces that might undo a right-hand thread. Left-handscrews are used on rotating items such as the left-hand grinding wheel on a bench grinder or the left hand pedal on a bicycle (both looking towards the equipment) or hub nuts on theleft side of some automobiles.

Fastener Types

Fasteners or screws come in a variety styles, head types and drive options. There is agreat variety of fasteners available and used throughout all industries and continents. WoodScrews, Sheet Metal Screws, Self-Drilling Screws, Drywall Screws, Machine Screws,Socket Head Cap Screws, Hex Head Screws and Set Screws to name a few. Almost all areavailable in a variety of head styles. Flat Head, Oval Head, Round Head, Truss Head,Binding, Fillister, Pan Head and Button Head just start the list. Some of them are available

Revision No.: -Revision Date: 08-11-10

Sheets: 5




in Standard or Security configurations, also known as Tamper-Proof or Tamper-Resistant.Most are available in fraction, number and metric sizes and all require some tool to installor remove them.

Head Styles

Flat Oval Round Truss Binding Pan Button

Fillister Socket Head Cap Low Head Cap Set (No Head) Hex

Many screw drives, including Phillips, Torx and Hexagonal, are also manufactured in aSecurity, (tamper-resistant or tamper-proof), form. These typically have a pin protruding inthe center of the screw head, requiring a special tool for installation and removal. In somevariants the pin is placed slightly off-center, requiring a correspondingly shaped bit.

The slotted screw also comes in a tamper-resistant one-way design with sloped or rampededges. The screw can be installed by using a standard Slotted driver, but the slopes or ramps require the use of a special tool for removal that prevents the driver from slipping outin the reverse direction.

What is the Difference between a Screw and Bolt?

A universally accepted distinction between a screw and a bolt does not exist.

In common usage the term screw refers to smaller (less than 1/4 inch) threaded fasteners,especially threaded fasteners with tapered shafts used in un-threaded substrates and theterm bolt refers to larger threaded fasteners that are designed to be used with nuts or intapped holes. The term machine screw is commonly used to refer to threaded fastenersthat are used with nuts or in tapped holes. The term lag bolt (also known less commonly asa lag screw) is used to refer to larger threaded fasteners with tapered shafts.

Various methods of distinguishing bolts and screws exist or have existed. These methodsconflict at times and can be confusing. Old SAE and USS standards made a distinctionbetween a bolt and a cap screw based on whether a portion of the shaft was un threadedor not. Cap screws had shafts that were threaded up to the head and bolts had partiallythreaded shafts. Today a bolt that has a completely threaded shaft might be referred to asa tap bolt.

bolt head types

Documents