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EnglishUnderstanding Metric Fasteners
2022.02.10
If we treat tapping machine as a gun , tap is bullet!
No matter DIN, ISO or JIS tap standard in the world, the size of tap is the key for user. The size of a metric
screw or bolt is specified as diameter, pitch and length,
in millimeters (millimeters is abbreviated "mm"). For nuts, size will appear as diameter and pitch. There is
an exception though—if pitch isn't specified,
the fastener is coarse threaded. Consider this size…
M8-1.0 x 20
Here's what the description means…
M = Metric thread designation
8 = Nominal diameter, in millimeters
1.0 = Pitch (distance from thread to thread), in millimeters
20 = Length, in millimeters (see below)
.
This example illustrates how a coarse threaded screw may appear…
M12 x 25 = 12 mm diameter, coarse thread is assumed (1.75 mm), 25 mm long, M12 is a matching
coarse threaded nut
If you normally work with inch fasteners, pitch can be a little confusing—pitch is the distance between
adjacent threads. In the example above, a pitch of 1.0 means that from one thread to the next thread,
the distance is 1.0 millimeter. Inch fasteners are described as threads per inch, which is sometimes
mistakenly called pitch.
If you need to know the threads per inch of a metric fastener, first convert pitch from millimeters to
inches (multiply by 0.03937), then divide 1 by that number.
Metric fasteners are usually classified as either coarse or fine, referring to their thread pitch, although
some sizes are available in an extra fine thread.
Coarse metric fasteners, when compared to standard "inch" fasteners (those commonly
used in North America),tend to be less coarse—their threads are more closely spaced—for
a comparable size. Fine metric fasteners canbe more or less fine, depending on size.
Coarse is the most common metric thread and, as we've mentioned,coarse is assumed
when pitch isn't specified.
No matter DIN, ISO or JIS tap standard in the world, the size of tap is the key for user. The size of a metric
screw or bolt is specified as diameter, pitch and length,
in millimeters (millimeters is abbreviated "mm"). For nuts, size will appear as diameter and pitch. There is
an exception though—if pitch isn't specified,
the fastener is coarse threaded. Consider this size…
M8-1.0 x 20
Here's what the description means…
M = Metric thread designation
8 = Nominal diameter, in millimeters
1.0 = Pitch (distance from thread to thread), in millimeters
20 = Length, in millimeters (see below)
.This example illustrates how a coarse threaded screw may appear…
M12 x 25 = 12 mm diameter, coarse thread is assumed (1.75 mm), 25 mm long, M12 is a matching
coarse threaded nut
If you normally work with inch fasteners, pitch can be a little confusing—pitch is the distance between
adjacent threads. In the example above, a pitch of 1.0 means that from one thread to the next thread,
the distance is 1.0 millimeter. Inch fasteners are described as threads per inch, which is sometimes
mistakenly called pitch.
If you need to know the threads per inch of a metric fastener, first convert pitch from millimeters to
inches (multiply by 0.03937), then divide 1 by that number.
Metric fasteners are usually classified as either coarse or fine, referring to their thread pitch, although
some sizes are available in an extra fine thread.
Coarse metric fasteners, when compared to standard "inch" fasteners (those commonly
used in North America),tend to be less coarse—their threads are more closely spaced—for
a comparable size. Fine metric fasteners canbe more or less fine, depending on size.
Coarse is the most common metric thread and, as we've mentioned,coarse is assumed
when pitch isn't specified.