Is 7/16 Bigger Than 1/2

METRIC FASTENERS

By Guy Avellon

Like it or not, Metrics is here to stay and we volition soon exist converting everything over to metrics. Thomas Jefferson was initiating the reform in his day and we accept been proverb "the metrics are coming" since 1975. Except for the automotive industry, nothing else has changed.
The U.S. is the last country in the world to not be exclusive users of the metric system in everything. We accept been using the metric system for decades in pharmaceuticals, photography, chemic manufacture, optics and fifty-fifty spark plugs.
As a unit of length measurement, everything is based on the meter, with a shift in the decimal signal to the left or right depending upon whether the value goes upwards or downward.

So, if a meter is 1.00, a tenth of a meter is a decimeter at 0.1m, a centimeter (cm) is one-hundredth of a meter at 0.01m and a milli-meter (mm), or one-thousandth of a meter is 0.001m. Therefore, i,000mm = 100cm = 1m. The numbers stay the aforementioned, only the decimal point shifts. This is actually like counting modify. Going larger, the side by side unit is 1,000 expressed as a kilometer (km), or one,000m.

An interesting fact that occurs with metric units; all units of weight, length and book are related. A cube which measures 10cm on each side has an surface area of one,000 cc (cubic centimeters). If the cube was filled with h2o, information technology would agree 1 liter (one 50, or i,000ml for milliliter) and weigh 1,000 g (grams) or i kg (kilogram).

Metric Standards
Until a few decades ago, there was no agreement to standards regarding metric fasteners from France, Italy, Frg, England or Nippon. The DIN (Deutsche Industries Norman) devised the virtually complete standards of any country, but there was however a demand for unification. The ISO (International Standards Organization) was formed.

The DIN standards have been modified to follow ISO recommendations. The The states coordinates their efforts with ISO through ANSI, the American National Standards Institute. Although there are notwithstanding some slight differences.

Fastener Designation
First, when ordering or identifying the dimensions of a metric fastener, all metric fasteners are preceded by the capitalized letter of the alphabet 'Thousand'. Then, similar to how inch series fasteners are identified, the bore is listed with the thread pitch, length and belongings class. For example: M12 x 1.five x 50, 10.9 Hex Cap Screw. This tells us the diameter is 12mm, the thread pitch is 1.5mm and the length is 50mm. The property class is a 10.ix.

Thread Pitch
Users must be aware that in that location are three types of thread pitches bachelor: the Standard thread, which is similar to the UNC; the Fine thread, like to the UNF; and the Japanese thread which is in between merely is used only on the M10 and M12 fasteners. For example; an M10 fastener can have a thread pitch of 1.0mm, 1.25mm and 1.50mm.
Identification is extremely of import because many metric sizes are very close to the inch series that the nut or fastener may be started simply additional tightening may result in thread stripping. For example, a ¼"-28 fastener has a bore of 0.250" compared with an M6 which measures 0.236". The difference is 0.014". The thread pitch on the M6 is 1.0 which is roughly equivalent to 25.6 threads-per-inch Vs the 28 TPI for the inch fastener. Non much difference and piece of cake to confuse.
The following chart cites other examples which illustrate the potential danger of mixing an inch with a metric fastener. The resultant assembly volition produce clamp loads from 25 to sixty% less than expected, providing the threads haven't stripped or have begun to strip, in which case the loads will be close to 100% lost.

Inch Threads vs. Metric Threads


Inch Bolts	Metric Nuts
x/32	M5 x 0.8
ane/iv″-28	M7 10 one.0
5/xvi″-eighteen	M8 x 1.0
3/eight″-16	M10 x one.5
vii/16″-xiv	M12 x 1.75
1/2″-13	M14 x ii
3/4″-ten	M20 10 2.5
3/iv″-16	M20 x 1.5
Metric Bolts	Inch Nuts
M12 10 1.25	one/2″-20
M18 10 2.5	3/four″-10
M18 10 1.5	iii/4″-sixteen
M24 x iii	i″-eight
M24 x 2	1″-12

Property Classes

Metric fastener strengths are named 'Property Class', not 'Grade'. All the same, the Belongings Classes are roughly equivalent to the SAE Grade system. The post-obit provides some examples.

Metric Grades

Property Form	SAE Grade
4.6	Course 1
4.8	Grade 1
iv.8	Grade 2
8.8	Course five
9.8	9% Stronger
10.9	Grade 8
xi.nine	NONE
12.ix	ASTM A574

The easiest way to tell a metric fastener's Property Classis past looking at the fastener for a numeric designation. These decimal numbers will exist marked on the hex caput or on the top or side of a socket caput fastener.

The fasteners volition have the decimal bespeak designation, nuts will non. For case, a 10.9 fastener's matching nut will take the marking of '10', not 10.nine.

The US automotive industry developed the 9.8 considering at that place were some sizes of the 8.viii fastener that would non provide the same strength equally an SAE Form v. It was a combination of fastener strength and caput dimension geometry for stress distribution.

I of the largest areas of confusion lies with the property class 8.viii designation. Many have confused this for the equivalent of the SAE Grade 8. The tensile strength deviation between 120 ksi and 150 ksi can be catastrophic in a disquisitional application.

Some other part to wait closely at for proper identification is the metric socket caput cap spiral. Unlike the U.s.a. socket head products, which come in simply one force grade of 180ksi upward to ½" and 170 ksi over ½", metric socket head products come in iii property classes; 8.eight, 10.9 and 12.nine. So be very aware of this when repairing European mechanism, so the proper forcefulness of socket product is replaced with the same type as was designed by the factory.

Thread Length
The DIN 931 and DIN 960 are essentially the aforementioned as the ISO requirement for thread length; 2 diameters plus 6mm for fasteners up to 125mm in length.

With the DIN 933 and DIN 961, however, the fastener is fully threaded to the caput regardless of length.

Wrench Sizes
Many mechanics have complained virtually the fact that they have had to use two wrenches to tighten the caput and nut of the aforementioned sized fastener. Fortunately, this but occurs in a couple of sizes. It is due to a basic disagreement betwixt DIN and ISO. The width across the flats (WAF) of DIN fasteners is 1mm larger on the M10, M12 and M14, while it is 2mm smaller on the M22.

Both types are available and sold in the US. Then information technology depends what specification the manufacture uses and who distributes them. A company buying from several distributors may terminate up with dissimilar sized nuts and bolt heads in the aforementioned storage bin.

Metric Wrench Sizes

NUT	DIN934	ISO
M10	17mm	16mm
M12	19mm	18mm
M14	22mm	21mm
M22	32mm	34mm

Metric Torque

Metric torque is expressed as a Newton – meter (N-m). The Newton is a normally used term in physics for forcefulness, named later on the scientist Sir Isaac Newton. A Newton equals 0.2248 pounds of force. Shifting the decimal point 3 places to the right, nosotros have a kilo-Newton (KN) or 224.81 pounds.

Fastener Strength

We have learned what the dissimilar property course designations are, but how practice they relate? Instead of using 'pounds-per-square-inch' (psi), metric terminology uses the term Pascal for its unit of force. Since these units become numerically large, they apply a prefix 'Mega' to course 'Mega Pascal' or MPa.

Therefore, 1 MPa is equal to 145 psi.
MPa 10 145 = psi
Psi x 0.0069 = MPa

It is also interesting to note that the belongings class numbers actually relate to the strength of the fastener. For example; an 8.viii fastener has the forcefulness of 830 MPa and the 10.9 is 1040 MPa. The metric designation number is actually its tensile strength.

It should also be noted here that while in that location are still nuts on the market with an 'eight' on it for use with the viii.8 fastener, ASTM A563M is only recognizing the property class ix nut for use with the 8.viii and 9.8 fasteners. Naturally, information technology has a minimum proof load stress of 900 MPa.