"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.
H and L limits are used for inch size ground thread taps. H (high) represents a pitch diameter that is larger than the basic pitch diameter, and L (low) represents a pitch diameter that is smaller. The number after the H or L, indicates the amount it is different than the basic pitch diameter.
M8 - metric thread 8mm. 6H - tolerance for internal thread, 6H class - for General purpose.
The first 6H refers to the Pitch Diameter tolerance. The second 6H refers to the minor diameter tolerance. Because screw thread plug gages do not look at the part minor diameter, the use of the minor diameter tolerance is irrelevant when considering the gage design parameters.
The tolerance position is the distance of the tolerance from the basic size of the thread profile. For nut threads there are two tolerance positions, H with a zero fundamental deviation (distance of the tolerance position from the basic size) and G with a positive fundamental deviation.
The upper case "H" is used to designate bore tolerance while the lower case "h" is used to designate shaft tolerances. Tolerances with lower case “h” are (minus) negative. Said another way, the capital letter "H" is for the hole, and lower case letter "h" is for the for shaft.
The standard also provides clear information. Then the tolerance class is assumed to be medium with the following tolerance classes: 6 h for threads M 1.6 and larger for internal threads and 6 g for threads M1. 6 and larger.
Pipe / G Threads are used for general purpose pipe fittings where pressure tight joints are not required on Threads.
G (supposedly from German/English “Gas”) are the cylindrical pipe threads with 55°apex angle used on originally inch based pipes. BSPP thread is often referred to as “G” threads, the two types of thread are the same parallel straight, the threads are measured in threads per inch.
The M10 x 1.5mm [6H] Metric Coarse Pitch - Go/No-Go Plug Thread Gauge (Insize 4130) has the following features: ISO 1502 Manufacturing Standard. 1.5mm Pitch.
abbreviation. (UK) A grade of pencil with lead that makes lighter marks than a pencil grade 5H; a pencil with extremely hard lead.
The M16 x 2mm [6H] Metric Coarse Pitch - Go/No-Go Plug Thread Gauge (JBO Johs Boss) has the following features: ISO 1502 Manufacturing Standard. Heat-Treated Steel Material. 2mm Pitch.
With metric threads, the larger tolerance grade number indicates a broader tolerance range. For example; 4H is approximately equivalent to Class 3B (precision quality), and 5H is approximately equivalent to Class 2B (commercial quality).
Size 6/0 is always the workhorse thread; we use it for making most of the patterns in our fly boxes: nymphs, freshwater streamers, beefier dry flies, and smaller saltwater patterns. This thread is stronger than size 8/0 so you can apply more tension when lashing materials to hooks.
6/0 would then be twice as thin, and 8/0 even thinner still. Once you think if it in this manner, it is pretty simple. But, there is no industry standard as to what that baseline zero should be for thickness, so every manufacturer has can have variations in what thread is rated.
Metric threads
Internal threads only use G and H, and external threads use a-h. As seen in Figure 2, H describes tolerance with zero deviation from the basic profile, and G describes tolerance with deviation above the basic profile.
G & R Thread Types
G is the international standard shorthand for BSPP - BSP Parallel threads. R is the standard for BSPT - BSP Tapered.
One example of this special terminology is the designation for different ACME thread forms, which may be labeled as G (General Purpose), C (Centralizing), or Stub.
G or R (Whitworth) or BSP (British Standard Pipe) Thread
Please note for the final determination whether you have a fitting with G or R-threads: G-threads, male as well as female, are cylindrical whereas you have to distinguish that male R-threads have a conical form and its female counterpart is cylindrical.
Large scale or G scale ( 45 mm or 13⁄4 inches, G gauge) is a track gauge for model railways which is often used for outdoor garden railways because of its size and durability.
6g has a wide variety of plugs options since this size is common for more than just stretched ears. Styles like tunnels and plugs are available alongside earrings, rings and barbells to guarantee an excellent fit for any piercing.
Metric fastener size designation nomenclature.
M10 x 1.5-6g-S means metric fastener thread profile M, fastener nominal size (nominal major diameter) 10 mm, thread pitch 1.5 mm, external thread tolerance class 6g, and thread engagement length group S ("short").
Major diameter: 6 mm. Pitch: 1.0 mm.
You can identify an M6 screw by measuring the diameter with a ruler. It'll be 6 mm, or slightly more than 7/32 inches (0.228″).