Fasteners and Fasteners types
Bolts and nuts
fasteners identification
Sizes and descriptions of bolts and nuts
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2. Fasteners
Fine Threaded Fasteners
•Stronger Thread
•Less likely to come loose
•Slow to assemble
•Easier to ruin the thread (cross thread)
Imperial threaded fasteners come in inch increments.
½”, 5/16”, 3/8”, 7/16” …
4. Fasteners
Metric Threaded Fasteners
•ISO Metric – International Organization for Standardization
•Most new vehicles have metric fasteners
•M6, M7, M8, M10, M12, M14 …
M8 X 25 X 1
Metric 8mm 25mm long Pitch (threads are 1mm apart)
5. Screws – A large and important family of fasteners.
The most common types of screws are:
Sheet-metal screws
Machine screws Set screws
Wood screws
“Mechanical devices for fastening things together. Essentially a
cylindrical or conical piece of metal threaded evenly around its
outside surface with an advancing spiral ridge and commonly
having a slotted head: it penetrates only by being turned, as with a
screwdriver.”
Use Categories
6. Bolts, Cap Screws, Nuts & Washers
Nomenclature of bolt-type fasteners tends to be confusing.
Bolts are usually used in plain holes drilled through the parts being
fastened.
Bolts are generally held in place with a mating nut.
When the nut for any bolt is turned down on wood, always use a flat
washer under the nut.
Cap screws are normally used in threaded holes, without a nut.
7. Machine Bolts/Cap Screws
Machine bolts have square or hexagonal heads.
Installed with a wrench.
Usually used if the parts to be joined are made of metal.
Cap screws generally look just like a machine bolt.
Slightly different application.
Screwed into threaded holes rather than being used with a nut.
8. Round-Head Bolts
Commonly used to fasten wood parts.
Most have a square neck under the head.
Also used to fasten steel parts with square
punched holes.
A Carriage Bolt is the most common type of
round-headed bolt to be used when working with
wood.
A Plow Bolt has a flat, tapered head that fits into
a countersunk hole – primarily used with metal parts.
Used in the marine industry for attaching
cutters and other parts to dredges.
Plow Bolt
Carriage Bolts
9. Stove Bolts are available with the same types of
head designs as wood screws, in diameters from
5/32” to 1/2” and in lengths from 3/8” to 6 inches.
Studs are another type of threaded fastener, which have no
head at all and is merely a steel rod with threads on both ends.
One end is screwed into a part, other parts are
assembled over the studs and screwed in place with a nut.
10. Stud is a headless bolt, threaded at both ends.
STUD : Terminology
Thread length
Length
Thread length
Drawing
representation
11. Other “ Bolts”
Some fasteners are referred to as bolts
but are actually screws.
A Lag Bolt is really a “heavy-duty screw”
with a square or hex head.
Designed to be driven with a wrench.
Available in lengths from 1” to 6” and diameters
from 1/4” to 1/2”.
A Hanger Bolt is a fastener that has wood screw style
threads on one end and machine threads on the other.
No head on this type of “bolt”.
Designed to be a hidden fastener.
12. Threads – External helical ribs on the body of a bolt at the end opposite
the head.
The diameter of a bolt is determined by the diameter of the crest of the
threads.
The length of most bolts (or machine screws) is determined by the
measuring from the bottom of the head to the end of the threads.
Flat head bolts are measured from the threaded end to the top of the head.
The Head Size determines what size wrench or socket must be used to
turn or hold the bolt or nut.
A square or hexagonal bolt head is measured across the “flats”.
Example – A ¾” wrench is needed to turn a ½” diameter bolt head.
Sizes and Descriptions
13. Nuts
Hex Nut – Most common on automobiles.
Castle Nut – locks with a cotter pin
Wing Nut – No tool required
Locking Nut – Nylon Patch (center, top)
Lug Nut – Taper face to help center the wheel
Speed Nut – Push-on (mostly screws)
14. Screws
Machine Screws –
no nut required ( usually less then ¼”
Passes through one piece and threads into other.
Sheet Metal Screws(self tapping) –
makes its own hole/threads
Set Screw – (allen wrench/no head)
Used for aligning pullies on the shaft.
15. Washers
Flat Washer –
Distributes pressure over a wider surface area.
Lock Washer - Prevents the fastener from loosening.
Used at high vibration places.
Bites into the material and the fastener.