Technical Information Unified Screw Thread Tolerancing System
This system is well known. It has now been accepted by ISO as the recommended tolerance for ISO inch threads down to 0.06 inch nominal diameter. The arrangement of the allowance and the various classes of pitch diameter tolerance for a normal length of engagement of the mating threads is shown in this diagram. The pitch diameter tolerance for Class 2A bolts is shown as 100 units, and the fundamental deviation and other tolerances are shown as percentages of the Class 2A tolerance. Figure 4.
Figure 4
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class 1B |
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nut
basic pitch diameter
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class 3B
97.5
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130
class 2B
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195 |
75 |
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class 3A |
30 |
100 |
30 150 |
bolt class 2A class 1A
Unified Taps The“ GH” System
This system provides for a range of pitch diameters for each size of tap: the height limit of pitch diameters being the basic pitch diameter plus increments or units of. 0005 ". It is designated by the letter“ GH” followed by a numeral indicating the number or units applying to the particular“ GH” size. The tap manufacturer’ s tolerance is applied as minus. This is the limit which will normally be supplied. Alternative“ GH” limits other than those shown in the price list can be made to special order.
GH Limits for JIS Roll Taps
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Inch + 0.0060 – + 0.0055 – + 0.0050 – + 0.0045 – + 0.0040 – + 0.0035 – + 0.0030 – + 0.0025 – + 0.0020 – + 0.0015 – + 0.0010 – + 0.0005 –
0 –
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GH1 |
GH Limits are applied to JIS Metric and Unified Thredflo Tap Threads due to market demands in the JIS standard.
GH2
GH3
GH4
GH5
GH6
GH7
GH8
GH9
GH12
GH11
GH10
GH Limits: Steps of 0.0005 " at 12.7 µ m
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Micron µ m
– + 140 – + 127 – + 114 – + 101 – + 89 – + 77 – + 64 – + 51 – + 39 – + 26 – + 13 – 0
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KL-TECH s. r. o | www. klte. cz |
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basic pitch dia. |
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For Sutton Tools Metric( mm) Roll / Fluteless Taps( Limit same as the“ RH” &“ G” Limits) GH Limits: Steps of 0.0127 mm N = GH number
GH LIMITS
Upper limit: 0.0005 " x N Lower limit:( 0.0005 " x N) – 0.0005
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