3. SYSTEMS OF THREAD
MEASUREMENT
ENGLISH SYSTEM
System of thread measurement uses a
fractional system to determine thread
diameter when 1/4” or larger.
Each diameter increases by 1/16” up to
about 1/2”
Thread diameters of 1/4”, 5/16”, 3/8”, 7/16”
1/2” are most commonly used
4. SYSTEMS OF THREAD MEASUREMENT
ENGLISH SYSTEM
These diameters are the most commonly used.
1/4 5/16 3/8 7/16 1/2
5. SYSTEMS OF THREAD MEASUREMENT
TABLE OF BOLT SIZES/THREAD PITCH-UNIFIED NATIONAL
COARSE (UNC) AND UNIFIED NATIONAL FINE (UNF)
Size-Fractional
(decimal)
Threads UNC Threads (UNF)
1/4" (.250") 20 28
5/16" (.3125") 18 24
3/8" (.375") 16 24
7/16" (.4375") 14 20
1/2" (.500") 13 20
9/16" (.5625") 12 18
5/8" (.625") 11 18
3/4" (.750") 10 16
6. Machine Screws Small Fasteners
1/4” And Smaller use a wire size number.
The smallest is Zero (0) and the largest is 14
#4, #6, #8, #10 and #12 are common sizes
Each has a standard UNC/UNF thread
specification.
Sizes are in increments of two
14 12 10 8 6
7. HEAD SIZE Vs DIAMETER
Head size of fastener is not size of fastener
Size is diameter of threaded portion of fastener
For Example
Bolt diameter - Wrench size American
1/4 - 7/16
5/16 - 1/2
3/8 - 9/16
7/16 - 11/16
½ - 3/4
9/16 - 7/8
5/8 - 15/16
8. HEAD SIZE Vs DIAMETER
Thanks for
The Table
Metric
9. BOLT LENGTH
MEASURED FROM UNDER HEAD TO END OF THREADS
USUALLY COME IN 1/4” INCREMENTS STARTING FROM
1/2” LENGTH
LONGEST BOLTS USED IN THE AUTOMOTIVE FIELD
ARE LESS THEN 6 INCHES LONG
10. FASTENER STRENGTH
FOR ENGLISH FASTENERS
STRENGTH OR HARDNESS IS
DETERMINED BY COUNTING SLASHES
OR POINTS ON IT’S HEAD
NO POINTS UNGRADED SHOULD NOT BE
USED ON AUTOMOTIVE APPLICATONS
3 POINTS GRADE 5 COMMONLY USED
6 POINTS GRADE 8 HIGH STRESSES
11. Bolt Strength
On U.S. bolts
add 2 to the #
of lines to get
the grade for
example 3
lines plus two
equals a
grade 5 Bolt
12. FASTENER STRENGTH FOR
METRIC FASTENERS
INDICATED BY NUMBER ON
HEAD (PROPERTY CLASS)
4.6, 4.8, 5.8, 8.8, 9.8 AND 10.9
Nuts will have a class of 4 or 6
13. FASTENER STRENGTH FOR NUTS
US Grade
Dots are used to represent the strength of Nuts
Or lines could be used
14. FASTENER STRENGTH FOR NUTS
US Grade
Grade 5 two lines at 90 degrees
Grade 8 two lines at 60 degrees
15. FASTENER STRENGTH
FOR NUTS
US Grade
Nut marking SAE Grade 8Nut marking SAE Grade 5
Grade 5 two lines at
90 degrees
Grade 8 two lines at
60 degrees
16. FASTENER STRENGTH FOR NUTS
Metric
Numbers are stamped to represent the
strength of Metric Nuts
17. FASTENER STRENGTH FOR NUTS
Do not use Grade 2 nuts on Grade 8 bolts. When you
torque the fastener it can strip out the nut and then it
will not hold.
Tips
23. THREAD TYPE
TYPE OR PITCH REFERS TO
CONSTRUCTION OF THREAD
NUMBER OF THREADS PER INCH
NATIONAL COARSE (NC OR USS)
NATIONAL FINE (NF OR SAE)
ALL 1/4” AND LARGER WILL BE EITHER
NC OR NF
1/4” AND SMALLER USES SPECIAL
DESIGNATION
24. American Standard bolts come in two thread pitch’s
NC National Coarse & NF National Fine
NF - National Fine NC - National Coarse
Fine & Coarse Thread
25. A. Pitch C. Diameter D. Thread length E. Screw length
F. Threads per inch G. Head size
How to measure a bolt
26. THREAD PITCH
From 0-1 shows that you have 7 TPI
Threads per inch. (US standard)
Metric you measure the pitch, from top
of thread to top of thread like # A
27. Thread pitch gauge
Used to find how many threads in an inch
come in metric and standard
Screw pitch gauge common name of this
29. Thread Designations US Threads
To write out Thread designations for US
bolts first you give the Diameter then the
Thread Pitch then the Length
D X TPI X L
½ X 13 X 2 ½
Take a bolt and give me the Thread
designations for it.
You can always add the grade of the bolt.
Such as grade 5
30. Thread Designations US Threads
So the first thing you have to do to write out
Thread designations is to measure the
Diameter.
D
½ inch
33. Thread Designations US Threads
You can always add the grade of the bolt.
Such as grade 5
D X TPI X L
½ X 13 X 2 ½ Gr 5 Zinc plated steel
Also what finish do you want it to be.
Stainless - Brass - Titanium - Zinc -
Plain - Black Oxide
34. METRIC FASTENERS
SIMILAR TO ENGLISH SYSTEM
THREAD DIAMETER IS EXPRESSED IN
MILLIMETERS (mm)
THREAD TYPE IS DIFFERENT
THREAD SIZE IS DETERMINED BY
MEASURING THE DISTANCE IN
MILLIMETERS FROM CREST OF ONE
THREAD TO CREST OF NEXT ONE.
Example 1.00, 1.25, AND 1.50
35. Thread Designations for Metric
To write out Thread designations for Metric
bolts first you give the Diameter then the
Thread Pitch then the Length. Only this
time it should be in millimeters
D X TPI X L
M12 X 1.50 X 60
You can always add the Class (grade) of
the bolt. Such as 4.8, 8.8, 10.8
52. Name the different clips
Internal
snap
ring
Pal nutExternal snap ring
Grease
Zerk
Blind Rivets
Wing Nut E-Clip
Split or Roll Hitch pin clip
Cotter
Pin
Set Screw
Stud
Thin or Jam nut
Speed
nuts
Lock
nut
53. Name the clips
Internal clip for a
drive line (U-Joint
Cross)
External clip for a
drive line
54. THREAD REPAIR
If a Bolt is too long & used in a blind
hole, it may bottom out, the head
can break off. Very hard to remove.
If a Bolt is broken off the first thing
you want to do is soak it with
penetrating oil.
If it is broken off flush use a hammer
and punch to see if it will turn out for
you.
Center punch in the center of the
fastener and use a left hand drill bit
to try to remove it.
55. THREAD REPAIR
If the end of the broken bolt is not flat use a
cutoff saw or grinder to flatten it out.
Another trick; if you cannot get the center
punch centered, (or if you mess up) try
using a small dremel grinder with a small
carbide bit to grind a spot in the center.
56. THREAD REPAIR
If end of bolt is sticking out use locking
pliers and try to remove it or
Reshape head, cut a screwdriver slot or
weld on a nut.
57. THREAD REPAIR
Matt Brubaker says,
Center punch, then drill a small hole all the way
through the stud, insert the straw of your favorite
penetrating oil and give a squirt, next pressurize the
hole with a rubber tipped blow gun for 30 sec. Another
squirt and 30 more seconds of air pressure.
Then I drill again for the largest possible easy out yet
leaving enough stud so the easy out doesn't dig into the
head and that has worked very well for me.
58. THREAD REPAIR
Timothy Filbin says, Drill a hole in the broken
stud or bolt, it doesn't need to be all the way
through. Heat up the broken stud or bolt
with a torch (a small propane unit will do), get
a small diameter birthday cake candle and
touch the end of the candle to the edge of the
exposed threads. The heat will melt the wax
and pull it into the threads just like when
soldering copper tubing.
59. THREAD REPAIR
Use a screw extractor sometimes called a easy
out to remove it.
First drill a hole in the center, all the way through
the fastener.
Lightly tap the extractor with a hammer and then
remove with a wrench. Use light pressure. Do
not use excessive force.
screw extractors
parallel fluted
I like these best
60. THREAD REPAIR
Do not break off the extractor or tap in the hole it
is harden steel almost impossible to get out.
If it does not come out drill out and retap the hole.
You may also try using heat and water (or
penetrating oil) to heat the area around the bolt
and cool the fastener. Just remember you could
wind up with a harden bolt in the hole.
64. Heli Coil EZ-LOK
Make sure you use the
right drill & tap size
THREAD REPAIR
THREAD REPAIR
65. Thread lockers
Anaerobic cures after the components are
put together
Locks Bolts & Studs against Vibration loosening
Four colors
Use on screws up to ¼ - Purple
# 242 Able to Remove ¼ to 3/4" Bolts - Blue
# 271 High Strength Hard to Remove 3/8 to 1" - Red
# 290 Wicking Grade for Preassembled Parts - Green
# could be different due to size of bottle
Clean and dry all parts removing dirt, oil, grease and/or any
foreign material
Watch video at
http://www.permatex.com/trainingvideos.htm
66. Purple Thread lockers
Low strength
Use on screws up to ¼
Applied BEFORE Assembly
Carburetors, relay locks,
headlamps, throttle body
assembly, choke assembly
and fuel injection set screws,
body panel mounting
fasteners
67. Blue Thread lockers
Medium Strength for all bolts ¼
or larger
Able to Remove with hand tools
Prevents parts from loosening
from vibration
Protects threads from corrosion
Recommend for valve cover
bolts,rocker arm nuts, carburetor
studs, motorcycle, jet skis
snowmobiles etc.
Applied BEFORE Assembly
68. Red Thread lockers
High Strength Hard to Remove
Works well for studs and press fit
Locks against heavy vibration
Requires extra effort to remove or
special tools like heat
Applied BEFORE Assembly
OEM specified as 271
69. Green Thread lockers
Wicking Grade for
Pre-assembled Parts
Use on Calibration and
adjustment screws
Applied AFTER Assembly
OEM specified as 290
There is also a Green High
Strength for sleeves
70. Thread / Pipe Sealant
Thread Sealant for metal
tapered pipe threads and
fittings replaces teflon tape
Suggested applications
Stainless steel fittings, head
bolts into through holes, oil PSI
sending units/sensors, oil and
coolant lines, intake manifold
switches, rear axle fill plug, fuel
fittings
71. Teflon Tape
Prevents leaks Just wrap tape
around threads
Use on stainless, aluminum,
plastic, iron, copper, or brass.
72. BOLT PAINTING
Many cars left the factory with painted bolts, nuts
and other assorted fasteners. The problem for the
garage restorer is that these freshly repainted pieces
chip and mar easily. So do what the factory did:
Bake the paint on. An old toaster oven is perfect for
this task--just set the oven to 325 degrees and let
the parts bake for a half-hour. This process
sometimes changes the color of paints
Thanks to enjoy the drive by SEMA
http://www.enjoythedrive.com/content/?id=7175
73. The end for now
most of these pictures were borrowed off of the web site
More training information at
http://www.boltdepot.com/fastener-information/Default.aspx
And the Permatex web site a big Thank you goes to both sites
& torque charts from
