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| techtalk:ref:tools032 [2022/03/27 07:35] – [Metric Nut/Bolt Threads] hippysmack | techtalk:ref:tools032 [2025/10/14 18:14] (current) – [JIC] hippysmack | ||
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| ====== Pitch to TPI Conversion Table ====== | ====== Pitch to TPI Conversion Table ====== | ||
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| The table below is a reprint from THA ((https:// | The table below is a reprint from THA ((https:// | ||
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| ====== US Nut/Bolt Threads ====== | ====== US Nut/Bolt Threads ====== | ||
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| US threads generally have 3 numbers although the last can be left off unless required. \\ | US threads generally have 3 numbers although the last can be left off unless required. \\ | ||
| The first number is a whole number and/or fraction, the second number is the threads per in (TPI), followed by the length in inches. \\ | The first number is a whole number and/or fraction, the second number is the threads per in (TPI), followed by the length in inches. \\ | ||
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| ====== Metric Nut/Bolt Threads ====== | ====== Metric Nut/Bolt Threads ====== | ||
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| Metric bolts are written down as an " | Metric bolts are written down as an " | ||
| The first number is the diameter, the second the thread pitch, and the third the length in millimeters. ((http:// | The first number is the diameter, the second the thread pitch, and the third the length in millimeters. ((http:// | ||
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| Your measurements may not be an exact match to the dims above but will be close enough to make a judgement on the metric counterpart size. \\ | Your measurements may not be an exact match to the dims above but will be close enough to make a judgement on the metric counterpart size. \\ | ||
| - | {{: | + | {{: |
| ====== Common Brake Line Threads ====== | ====== Common Brake Line Threads ====== | ||
| Most brake systems use flared fittings since they have strong metal to metal connections. \\ | Most brake systems use flared fittings since they have strong metal to metal connections. \\ | ||
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| ====== NPT Pipe Threads ====== | ====== NPT Pipe Threads ====== | ||
| - | NPT stands for National Pipe Thread. Descriptions are commonly used as either straight (NPS) or tapered (NPT). ((DR DICK of the XLFORUM | + | NPT stands for National Pipe Thread. Descriptions are commonly used as either straight (NPS) or tapered (NPT). ((DR DICK of the XLFORUM |
| Pipe thread sizes do not refer to any physical dimension. \\ | Pipe thread sizes do not refer to any physical dimension. \\ | ||
| NPT has flattened peaks and troughs where BSP is rounded. NPT has a thread angle of 60º where BSP is 55º. \\ | NPT has flattened peaks and troughs where BSP is rounded. NPT has a thread angle of 60º where BSP is 55º. \\ | ||
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| ** Little known fact**: \\ | ** Little known fact**: \\ | ||
| - | All iron heads pipe threads used in cases, rocker boxes, and oil pumps are straight female thread, fitted with tapered thread male fittings.((DR DICK of the XLFORUM | + | All iron heads pipe threads used in cases, rocker boxes, and oil pumps are straight female thread, fitted with tapered thread male fittings.((DR DICK of the XLFORUM |
| This holds true for Evo Sportsters also. \\ | This holds true for Evo Sportsters also. \\ | ||
| - | * The sizes in the chart below are the major dia of the male straight thread (as the pipe OD is the major). \\ And the major dia. of a tapered male thread at it's big end. ((DR DICK of the XLFORUM | + | * The sizes in the chart below are the major dia of the male straight thread (as the pipe OD is the major). \\ And the major dia. of a tapered male thread at it's big end. ((DR DICK of the XLFORUM |
| - | * The tapered thread has it's diameter reduced on a taper of .0625" per inch of thread length. Almost all hardware store fittings will be tapered thread.((DR DICK of the XLFORUM | + | * The tapered thread has it's diameter reduced on a taper of .0625" per inch of thread length. Almost all hardware store fittings will be tapered thread.((DR DICK of the XLFORUM |
| ^{{techtalk: | ^{{techtalk: | ||
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| ====== AN and JIC Flared Fitting Threads ====== | ====== AN and JIC Flared Fitting Threads ====== | ||
| + | ==== Flare Angle Compatibility ==== | ||
| + | * Flared connections generally consist of 2 parts (a flared fitting or a flared tubing end connected to another part that has the same receiving flared angle seat so that both flared portions ensure metal-to-metal contact between the mated parts to preventing leaks and maintain system pressure. ((https:// | ||
| + | * It's important that the flare angle is the same for the fitting/ | ||
| + | * Accurately identifying the flare angle requires a dedicated flare gauge. This tool confirms if the angle is precisely 37 or 45 degrees, eliminating guesswork. Visual inspection alone is often insufficient and can lead to costly fitting errors. ((https:// | ||
| + | * Thread sizes have nothing to do with flare angles. While flare fittings have threads, the flare angle is independent of the thread size or pitch. Two fittings can have identical threads but different flare angles, making angle verification a distinct and essential step in proper fitting identification and selection. ((https:// | ||
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| ==== AN ==== | ==== AN ==== | ||
| AN (or Army/Navy) was never intended to characterize an entire fluid system, and is mostly designed as a thread specification. \\ | AN (or Army/Navy) was never intended to characterize an entire fluid system, and is mostly designed as a thread specification. \\ | ||
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| The sizes run the same as other SAE fittings (IE: SAE #4, #6, #12, etc) so they are very easy to size. \\ | The sizes run the same as other SAE fittings (IE: SAE #4, #6, #12, etc) so they are very easy to size. \\ | ||
| JIC fittings are dimensionally identical to AN (Army-Navy) fittings, but are produced to less exacting tolerances and are generally less costly. ((https:// | JIC fittings are dimensionally identical to AN (Army-Navy) fittings, but are produced to less exacting tolerances and are generally less costly. ((https:// | ||
| - | AE 45° flare fittings are similar in appearance, but are not interchangeable, | + | SAE 45° flare fittings are similar in appearance, but are not interchangeable, |
| * You can measure male JIC threads by either using a caliper or simply laying a fitting across a tape measure. \\ Measure the OD of the threads and count the number of threads per inch to confirm with the chart below. \\ Thread OD will not exactly match the SAE thread size but will get you close enough if you have a JIC fitting. | * You can measure male JIC threads by either using a caliper or simply laying a fitting across a tape measure. \\ Measure the OD of the threads and count the number of threads per inch to confirm with the chart below. \\ Thread OD will not exactly match the SAE thread size but will get you close enough if you have a JIC fitting. | ||
| + | |||
| + | ==== SAE ==== | ||
| + | SAE (Society of Automotive Engineers) is a global organization that develops engineering standards for the automotive industry. \\ | ||
| + | Characteristics of SAE Flare Fittings are 45° flare angles (which distinguishes them from JIC fittings, which have a 37° flare angle.\\ | ||
| + | Flared SAE fittings are also used in a wide range of applications including braking systems, fuel lines, hydraulic systems, refrigeration / air conditioning and plumbing systems. \\ | ||
| ^{{techtalk: | ^{{techtalk: | ||
