But the size of a metric fastener is more accurately specified using diameter, pitch and length dimensions, in millimeters. Metric nuts and bolts are commonly referenced using ‘M’ sizes, for example: M3, M8, M12.
Metric bolts sizes m1.6 iso#
Part 1 is based on ISO 965/1 and ISO 965/3 providing the principles and basic data for specifications of ISO metric screw threads.Īnd BS3643 part 2 provides tabulated diameters and tolerances for coarse and fine pitch threads, based on ISO 965/2. BS3643 Parts 1&2īS3643 defines the limits and tolerances for ISO screw thread gauges. In this brief guide we provide an introduction to standard ISO metric sizes for nuts and bolts which will hopefully help dispel any confusion. In most circumstances, it’s absolutely vital that the right size of fastening is used. Note: If you know the DIN or ISO number of the fastener you're looking for, you can use our search function to locate it quickly.Nuts and bolts are essential fastenings, critical in the safe assembly of machinery, equipment, furniture and much more. Machine Screw Hex Nut, Finished Hex Jam Nut Descriptions of DIN and ISO designations. Following is a table of common DIN and ISO numbers and a brief description of the fastener… Table 4. You may also see JIS - Japanese Industrial Standard and ANSI - American National Standards Institute specified. Consequently, they are referred to by the applicable standard number. Metric fasteners are commonly manufactured to meet standards set by DIN - German Institute for Standardization or ISO - International Organization for Standardization. Measure oval heads from the largest diameter point-where the dome top meets the conical bearing surface-to the tip. For flat heads, length includes head height.
For button, cheese, hex, pan, socket and low socket heads, measure length from under the head. Length is measured the same as inch fasteners, except in millimeters. Comparison of metric and inch fastener sizes. The table below compares various metric sizes to the closest inch equivalent… Table 3. But the M3.5-0.35 has close to double the number of threads per inch of a 6-40, so its threads are very closely spaced (0.014 inches, or 0.35 mm). When you look at fine M14-1.5 and 9/16-18 fasteners, however, the 9/16-18 is finer-it has more threads per inch. (M3.5-0.6 and M3.5-.6 are exactly the same-the "0" is included to make sure that the decimal point isn't missed.)
The same goes for a coarse M3.5-0.6 and a 6-32 screw-the threads of the 6-32 are more widely spaced so, again, it will have fewer threads for the same length. A 9/16-12 screw, which is comparable in diameter and is also coarse, has its threads spaced 0.083 inches, which are farther apart, so there will be fewer threads per unit of measure (we used an inch in the table above). The threads of an M14-2.0 screw, which is coarse, are spaced 0.079 inches (2.0 mm). Comparison of metric and inch fastener threads. Coarse is the most common metric thread and, as we've mentioned, coarse is assumed when pitch isn't specified. Fine metric fasteners can be more or less fine, depending on size. 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. 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. Fastener thread pitch in millimeters and inches. 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. Inch fasteners are described as threads per inch, which is sometimes mistakenly called pitch. In the example above, a pitch of 1.0 means that from one thread to the next thread, the distance is 1.0 millimeter.
If you normally work with inch fasteners, pitch can be a little confusing-pitch is the distance between adjacent threads. (To avoid confusion, we always include the thread pitch for both coarse and fine metric fasteners.) M12 x 25 = 12 mm diameter, coarse thread is assumed (1.75 mm), 25 mm long
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