For identification purposes, hydraulic tube fittings and connectors can be divided into six different thread types: UN/UNF, NPT/NPTF, BSPP (BSP, parallel), BSPT (BSP, tapered), metric parallel, and metric tapered. Three are parallel (UN/UNF, BSPP, metric parallel) and three are tapered (NPT/NPTF, BSPT, metric tapered).
Size for size a fine thread is stronger than a coarse thread . This is both in tension (because of the larger stress area) and shear (because of their larger minor diameter). Fine threads have also less tendency to loosen since the thread incline is smaller and hence so is the off torque.
Coarse threads are those with larger pitch (fewer threads per axial distance), and fine threads are those with smaller pitch (more threads per axial distance). Coarse threads have a larger threadform relative to screw diameter, where fine threads have a smaller threadform relative to screw diameter.
For metric fasteners, you will see a M8 x 1.25 or an M8 x 1. For thread pitch, the distance between two points is the second number meaning the higher the number the fewer threads there are. This means the M8 x 1.25 is the coarse threading and the M8 x 1 is the fine thread.
Thread Pitch. Metric fasteners are specified with a thread pitch instead of a thread count. The thread pitch is the distance between threads expressed in millimeters (measured along the length of the fastener). For example a thread pitch of 1.5 means that the distance between one thread and the next is 1.5mm.
Coarse threads are those with larger pitch (fewer threads per axial distance), and fine threads are those with smaller pitch (more threads per axial distance). Coarse threads have a larger threadform relative to screw diameter, where fine threads have a smaller threadform relative to screw diameter.
| Tap size | Basic major dia (mm) | Basic major dia (inch) |
|---|
| M20 x 2.5 | 20mm | .7874 |
| M20 x 1.5 | 20mm | .7874 |
| M22 x 2.5 | 22mm | .8661 |
| M22 x 1.5 | 22mm | .8661 |
Thread Pitch and Thread Count (TPI)
TPI stands for Threads Per Inch. This is simply a count of the number of threads per inch measured along the length of a fastener. Metric Fasteners use a thread Pitch (see below). In general smaller fasteners have finer threads, so the thread count is higher.They also have larger tensile stress areas which in turn make them stronger in tension than coarse threads. Fine threads also possess larger minor diameters, which provide high shear strengths. Coarse threads tap better into brittle materials and are less likely to cross thread.
Coarse thread can be bought from the Trade Vendor at the wagon in Brill, close to the tavern/inn. As for the bats, Vampiric are around lvl.
Coarse drywall screws feature coarse threads to secure gypsum boards to studs. Fine drywall screws feature smaller heads and are used to secure drywall to metal studs. Self-drilling screws and pan-head screws can be used with metal studs or frames. Trim-head screws are used to attach wood trim over gypsum boards.
Coarse-threaded screws are less likely to jam if the screw is inserted at an angle. Coarse-threaded screws are used in softer materials such as soft/hard wood, plastic or plasterboard. This is because their threads are able to grip the soft fibres of the material and hold the screw in place.
Thread galling occurs during installation when pressure and friction cause bolt threads to seize to the threads of a nut or tapped hole. It is also known as "cold welding". Once a fastener has seized up from galling it is typically impossible to remove without cutting the bolt or splitting the nut.
Generally, there are two thread series, namely The ISO Metric Screw Thread (in millimetres) and The Unified Screw Thread (in inches). For both these series, there are two types of threads – fine thread and coarse thread.
Definition of depth of thread. : the distance between the crest and the base of a screw thread measured radially.
The 5g indicates the tolerance class for the pitch diameter and 6g is the tolerance class for the major diameter. For example: M12 x 1 - 6H/5g6g indicates a tolerance class of 6H for the nut (female) thread and a 5g tolerance class for the pitch diameter with a 6g tolerance class for the major diameter.
Inch & Metric Thread Standards. Metric thread sizes are specified differently than inch thread sizes. For example, a 3/8-16 (coarse) thread has a 3/8" nominal major diameter and 16 threads per inch, while a 3/8-24 (fine) thread has the same nominal major diameter and 24 threads per inch.
The 5g indicates the tolerance class for the pitch diameter and 6g is the tolerance class for the major diameter. For example: M12 x 1 - 6H/5g6g indicates a tolerance class of 6H for the nut (female) thread and a 5g tolerance class for the pitch diameter with a 6g tolerance class for the major diameter.
m8 means metric thread 8mm of ISO standard and 6H refers to tolerance of threaded hole (know more about it in ISO 2768)
"G" designates Ground Thread. "H" designates the pitch diameter is on high side of basic. These two letters (GH) are followed by a numeral indicating the Tolerance of Pitch diameter oversize.
Re: Most common metric bolt sizes
Used to be (back in the 70's and 80's) that European manufacturers used the 13mm and 10mm fasteners the most; followed by the 14, 17, and 19mm. The Asian manufacturers used the 12mm and 10mm as the most common, followed by the 15, 17 and 19mm.The common V-thread standards (ISO 261 and Unified Thread Standard) include a coarse pitch and a fine pitch for each major diameter. For example, ?1⁄2-13 belongs to the UNC series (Unified National Coarse) and ?1⁄2-20 belongs to the UNF series (Unified National Fine).
METRIC THREAD -- FINE PITCH -- M (1 mm - 28 mm)
M10 means a 10 millimeter outer diameter for the bolt or whatever piece it is; M12 means 12 millimeters. The part after the 'x' is the pitch -- how many mm a thread is wide. To figure out which you have, you can measure the existing part with calipers and a thread gauge.
