JRVAL
Jul 29 20260. Latest Drawing Standards (Focus on Flanges & General Tolerances)
Technical requirements in drawings must be updated to the following GB standards. Do NOT use obsolete standards.
| Item | Obsolete Standard | Current Standard (Mandatory) |
|---|---|---|
| Limits and Fits System (IT Grades & Deviations) | GB/T 1800.1-2009 | GB/T 1800.1-2020 |
| General Tolerances for Linear Dimensions | - | GB/T 1804-2000 (Default: Class m) |
| General Geometrical Tolerances | - | GB/T 1184-1996 (Default: Class K) |
| Integral Steel Pipe Flanges (PN Series) | GB/T 9113-2010 | GB/T 9124.1-2019 |
| Casting Dimensional Tolerances (Rough) | GB/T 6414-2017 (Abolishing Dec 2025) |
GB/T 42124.3-2025 (New GPS Standard) |
| Surface Texture (Roughness Parameters & Values) | GB/T 1031-1995 | GB/T 1031-2009 |
| Metal Valves Face-to-Face Dimensions | GB/T 12221-2005 (Abolishing May 2026) |
GB/T 12221-2025 (Newly Released) |
1. Standard Tolerance Grades (IT) & Fits (Ref: GB/T 1800.1-2020)
Core Concept: Software calculates values automatically; this table guides you on "which grade to choose". Lower numbers mean higher precision and cost. The valve industry rarely uses precision higher than IT6.
| Tolerance Grade | Machining Difficulty & Cost | Typical Valve Applications (Direct Reference) |
|---|---|---|
| IT6 - IT7 | Precision Grinding / High Cost | Valve Stem (Shaft): Usually f7 or e7. Bearing seats, core moving parts requiring precise sliding. |
| IT8 - IT9 | Fine Turning, Reaming / Medium | Body Bore, Bushing Bore: Usually H8 or H9. Clearance fit with valve stem (e.g., H8/f7). |
| IT10 - IT11 | Rough Turning, Milling / Low Cost | Non-core fits: Parts that just need assembly clearance, packing gland OD, handwheel connection bores. |
1.1 Standard Tolerance Values Quick Reference (Unit: μm, 1 mm = 1000 μm)
| Nominal Size (mm) | Standard Tolerance Grade (IT) Values (μm) | ||||||
|---|---|---|---|---|---|---|---|
| Over (>) | Up to (≤) | IT6 | IT7 | IT8 | IT9 | IT10 | IT11 |
| 3 | 6 | 8 | 12 | 18 | 30 | 48 | 75 |
| 6 | 10 | 9 | 15 | 22 | 36 | 58 | 90 |
| 10 | 18 | 11 | 18 | 27 | 43 | 70 | 110 |
| 18 | 30 | 13 | 21 | 33 | 52 | 84 | 130 |
| 30 | 50 | 16 | 25 | 39 | 62 | 100 | 160 |
| 50 | 80 | 19 | 30 | 46 | 74 | 120 | 190 |
| 80 | 120 | 22 | 35 | 54 | 87 | 140 | 220 |
| 120 | 180 | 25 | 40 | 63 | 100 | 160 | 250 |
| 180 | 250 | 29 | 46 | 72 | 115 | 185 | 290 |
| 250 | 315 | 32 | 52 | 81 | 130 | 210 | 320 |
| 315 | 400 | 36 | 57 | 89 | 140 | 230 | 360 |
| 400 | 500 | 40 | 63 | 97 | 155 | 250 | 400 |
| 500 | 630 | 44 | 70 | 110 | 175 | 280 | 440 |
| 630 | 800 | 50 | 80 | 125 | 200 | 320 | 500 |
| 800 | 1000 | 56 | 90 | 140 | 230 | 360 | 560 |
| 1000 | 1250 | 66 | 105 | 165 | 260 | 420 | 660 |
| 1250 | 1600 | 78 | 125 | 195 | 310 | 500 | 780 |
| 1600 | 2000 | 92 | 150 | 230 | 370 | 600 | 920 |
| 2000 | 2500 | 110 | 175 | 280 | 440 | 700 | 1100 |
| 2500 | 3150 | 135 | 210 | 330 | 540 | 860 | 1350 |
1.2 Fundamental Deviations for Holes (A-M)
Based on GB/T 1800.1-2020 / ISO 286-1. Unit: μm.
This table defines the starting position (Upper/Lower limit) of the tolerance zone. Used in conjunction with standard IT grades.
This table defines the starting position (Upper/Lower limit) of the tolerance zone. Used in conjunction with standard IT grades.
| Over (>) |
Up to (≤) |
Fundamental Deviation Values | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Lower Limit Deviation, EI | JS | Upper Limit Deviation, ES | ||||||||||||||||||
| All IT Grades | IT6 | IT7 | IT8 | ≤IT8 >IT8 | ≤IT8 >IT8 | |||||||||||||||
| Aa | Ba | C | CD | D | E | EF | F | FG | G | H | J | Kc,d | Mb,c,d | |||||||
| - | 3 | +270 | +140 | +60 | +34 | +20 | +14 | +10 | +6 | +4 | +2 | 0 | ±ITn / 2 | +2 | +4 | +6 | 0 | 0 | -2 | -2 |
| 3 | 6 | +270 | +140 | +70 | +46 | +30 | +20 | +14 | +10 | +6 | +4 | 0 | +5 | +6 | +10 | -1+Δ | 0 | -4+Δ | -4 | |
| 6 | 10 | +280 | +150 | +80 | +56 | +40 | +25 | +18 | +13 | +8 | +5 | 0 | +5 | +8 | +12 | -1+Δ | 0 | -6+Δ | -6 | |
| 10 | 14 | +290 | +150 | +95 | +70 | +50 | +32 | +23 | +16 | +10 | +6 | 0 | +6 | +10 | +15 | -1+Δ | 0 | -7+Δ | -7 | |
| 14 | 18 | +290 | +150 | +95 | +70 | +50 | +32 | +23 | +16 | +10 | +6 | 0 | +6 | +10 | +15 | -1+Δ | 0 | -7+Δ | -7 | |
| 18 | 24 | +300 | +160 | +110 | +85 | +65 | +40 | +28 | +20 | +12 | +7 | 0 | +8 | +12 | +20 | -2+Δ | 0 | -8+Δ | -8 | |
| 24 | 30 | +300 | +160 | +110 | +85 | +65 | +40 | +28 | +20 | +12 | +7 | 0 | +8 | +12 | +20 | -2+Δ | 0 | -8+Δ | -8 | |
| 30 | 40 | +310 | +170 | +120 | +100 | +80 | +50 | +35 | +25 | +15 | +9 | 0 | +10 | +14 | +24 | -2+Δ | 0 | -9+Δ | -9 | |
| 40 | 50 | +320 | +180 | +130 | +100 | +80 | +50 | +35 | +25 | +15 | +9 | 0 | +10 | +14 | +24 | -2+Δ | 0 | -9+Δ | -9 | |
| 50 | 65 | +340 | +190 | +140 | +100 | +60 | +30 | +10 | 0 | +13 | +18 | +28 | -2+Δ | 0 | -11+Δ | -11 | ||||
| 65 | 80 | +360 | +200 | +150 | +100 | +60 | +30 | +10 | 0 | +13 | +18 | +28 | -2+Δ | 0 | -11+Δ | -11 | ||||
| 80 | 100 | +380 | +220 | +170 | +120 | +72 | +36 | +12 | 0 | +16 | +22 | +34 | -3+Δ | 0 | -13+Δ | -13 | ||||
| 100 | 120 | +410 | +240 | +180 | +120 | +72 | +36 | +12 | 0 | +16 | +22 | +34 | -3+Δ | 0 | -13+Δ | -13 | ||||
| 120 | 140 | +460 | +260 | +200 | +145 | +85 | +43 | +14 | 0 | +18 | +26 | +41 | -3+Δ | 0 | -15+Δ | -15 | ||||
| 140 | 160 | +520 | +280 | +210 | +145 | +85 | +43 | +14 | 0 | +18 | +26 | +41 | -3+Δ | 0 | -15+Δ | -15 | ||||
| 160 | 180 | +580 | +310 | +230 | +145 | +85 | +43 | +14 | 0 | +18 | +26 | +41 | -3+Δ | 0 | -15+Δ | -15 | ||||
| 180 | 200 | +660 | +340 | +240 | +170 | +100 | +50 | +15 | 0 | +22 | +30 | +47 | -4+Δ | 0 | -17+Δ | -17 | ||||
| 200 | 225 | +740 | +380 | +260 | +170 | +100 | +50 | +15 | 0 | +22 | +30 | +47 | -4+Δ | 0 | -17+Δ | -17 | ||||
| 225 | 250 | +820 | +420 | +280 | +170 | +100 | +50 | +15 | 0 | +22 | +30 | +47 | -4+Δ | 0 | -17+Δ | -17 | ||||
| 250 | 280 | +920 | +480 | +300 | +190 | +110 | +56 | +17 | 0 | +25 | +36 | +55 | -4+Δ | 0 | -20+Δ | -20 | ||||
| 280 | 315 | +1050 | +540 | +330 | +190 | +110 | +56 | +17 | 0 | +25 | +36 | +55 | -4+Δ | 0 | -20+Δ | -20 | ||||
| 315 | 355 | +1200 | +600 | +360 | +210 | +125 | +62 | +18 | 0 | +29 | +39 | +60 | -4+Δ | 0 | -21+Δ | -21 | ||||
| 355 | 400 | +1350 | +680 | +400 | +210 | +125 | +62 | +18 | 0 | +29 | +39 | +60 | -4+Δ | 0 | -21+Δ | -21 | ||||
| 400 | 450 | +1500 | +760 | +440 | +230 | +135 | +68 | +20 | 0 | +33 | +43 | +66 | -5+Δ | 0 | -23+Δ | -23 | ||||
| 450 | 500 | +1650 | +840 | +480 | +230 | +135 | +68 | +20 | 0 | +33 | +43 | +66 | -5+Δ | 0 | -23+Δ | -23 | ||||
| 500 | 560 | +260 | +145 | +76 | +22 | 0 | 0 | -26 | ||||||||||||
| 560 | 630 | +260 | +145 | +76 | +22 | 0 | 0 | -26 | ||||||||||||
| 630 | 710 | +290 | +160 | +80 | +24 | 0 | 0 | -30 | ||||||||||||
| 710 | 800 | +290 | +160 | +80 | +24 | 0 | 0 | -30 | ||||||||||||
| 800 | 900 | +320 | +170 | +86 | +26 | 0 | 0 | -34 | ||||||||||||
| 900 | 1000 | +320 | +170 | +86 | +26 | 0 | 0 | -34 | ||||||||||||
| 1000 | 1120 | +350 | +195 | +98 | +28 | 0 | 0 | -40 | ||||||||||||
| 1120 | 1250 | +350 | +195 | +98 | +28 | 0 | 0 | -40 | ||||||||||||
| 1250 | 1400 | +390 | +220 | +110 | +30 | 0 | 0 | -48 | ||||||||||||
| 1400 | 1600 | +390 | +220 | +110 | +30 | 0 | 0 | -48 | ||||||||||||
| 1600 | 1800 | +430 | +240 | +120 | +32 | 0 | 0 | -58 | ||||||||||||
| 1800 | 2000 | +430 | +240 | +120 | +32 | 0 | 0 | -58 | ||||||||||||
| 2000 | 2240 | +480 | +260 | +130 | +34 | 0 | 0 | -68 | ||||||||||||
| 2240 | 2500 | +480 | +260 | +130 | +34 | 0 | 0 | -68 | ||||||||||||
| 2500 | 2800 | +520 | +290 | +145 | +38 | 0 | 0 | -76 | ||||||||||||
| 2800 | 3150 | +520 | +290 | +145 | +38 | 0 | 0 | -76 | ||||||||||||
Notes / Exceptions:
a For nominal size ≤ 1 mm, fundamental deviations A and B do not apply.
b Exception: For nominal sizes > 250 mm up to 315 mm for tolerance class M6, ES = -9 μm (calculated result is not -11 μm).
c To determine the specific values of K and M involving Δ, refer to standard section 4.3.2.5.
d For the specific value of Δ, refer to Table 3 in the standard (GB/T 1800.1 / ISO 286-1).
* JS formula: Deviation = ±ITn / 2, where n is the IT grade number.
a For nominal size ≤ 1 mm, fundamental deviations A and B do not apply.
b Exception: For nominal sizes > 250 mm up to 315 mm for tolerance class M6, ES = -9 μm (calculated result is not -11 μm).
c To determine the specific values of K and M involving Δ, refer to standard section 4.3.2.5.
d For the specific value of Δ, refer to Table 3 in the standard (GB/T 1800.1 / ISO 286-1).
* JS formula: Deviation = ±ITn / 2, where n is the IT grade number.
1.3 Fundamental Deviations for Shafts (a-j)
Based on GB/T 1800.1-2020 / ISO 286-1. Unit: μm.
Upper limit deviation (es) for shafts a~h. Lower limit deviation (ei) for shaft j.
Upper limit deviation (es) for shafts a~h. Lower limit deviation (ei) for shaft j.
| Over (>) |
Up to (≤) |
Upper Limit Deviation, es | js | Lower Limit Dev., ei | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| All IT Grades | j | ||||||||||||||||
| aa | ba | c | cd | d | e | ef | f | fg | g | h | IT5 & IT6 | IT7 | IT8 | ||||
| - | 3 | -270 | -140 | -60 | -34 | -20 | -14 | -10 | -6 | -4 | -2 | 0 | Deviation = ±ITn / 2 | -2 | -4 | -6 | |
| 3 | 6 | -270 | -140 | -70 | -46 | -30 | -20 | -14 | -10 | -6 | -4 | 0 | -2 | -4 | - | ||
| 6 | 10 | -280 | -150 | -80 | -56 | -40 | -25 | -18 | -13 | -8 | -5 | 0 | -2 | -5 | |||
| 10 | 14 | -290 | -150 | -95 | -70 | -50 | -32 | -23 | -16 | -10 | -6 | 0 | -3 | -6 | - | ||
| 14 | 18 | ||||||||||||||||
| 18 | 24 | -300 | -160 | -110 | -85 | -65 | -40 | -25 | -20 | -12 | -7 | 0 | -4 | -8 | - | ||
| 24 | 30 | ||||||||||||||||
| 30 | 40 | -310 | -170 | -120 | -100 | -80 | -50 | -35 | -25 | -15 | -9 | 0 | -5 | -10 | - | ||
| 40 | 50 | -320 | -180 | -130 | |||||||||||||
| 50 | 65 | -340 | -190 | -140 | - | -100 | -60 | - | -30 | - | -10 | 0 | -7 | -12 | - | ||
| 65 | 80 | -360 | -200 | -150 | |||||||||||||
| 80 | 100 | -380 | -220 | -170 | - | -120 | -72 | - | -36 | - | -12 | 0 | -9 | -15 | - | ||
| 100 | 120 | -410 | -240 | -180 | |||||||||||||
| 120 | 140 | -460 | -260 | -200 | - | -145 | -85 | - | -43 | - | -14 | 0 | -11 | -18 | - | ||
| 140 | 160 | -520 | -280 | -210 | |||||||||||||
| 160 | 180 | -580 | -310 | -230 | |||||||||||||
| 180 | 200 | -660 | -340 | -240 | - | -170 | -100 | - | -50 | - | -15 | 0 | -13 | -21 | - | ||
| 200 | 225 | -740 | -380 | -260 | |||||||||||||
| 225 | 250 | -820 | -420 | -280 | |||||||||||||
| 250 | 280 | -920 | -480 | -300 | - | -190 | -110 | - | -56 | - | -17 | 0 | -16 | -26 | - | ||
| 280 | 315 | -1050 | -540 | -330 | |||||||||||||
| 315 | 355 | -1200 | -600 | -360 | - | -210 | -125 | - | -62 | - | -18 | 0 | -18 | -28 | - | ||
| 355 | 400 | -1350 | -680 | -400 | |||||||||||||
| 400 | 450 | -1500 | -760 | -440 | - | -230 | -135 | - | -68 | - | -20 | 0 | -20 | -32 | - | ||
| 450 | 500 | -1650 | -840 | -480 | |||||||||||||
Notes:
a For nominal size ≤ 1 mm, fundamental deviations a and b do not apply.
a For nominal size ≤ 1 mm, fundamental deviations a and b do not apply.
1.4 Base Hole System Fits (Preferred)
| Shaft Hole | Clearance Fits | Transition Fits | Interference Fits | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| a | b | c | d | e | f | g | h | js | k | m | n | p | r | s | t | u | v | x | y | z | |
| H6 |
H6f5
|
H6g5
|
H6h5
|
H6js5
|
H6k5
|
H6m5
|
H6n5
|
H6p5
|
H6r5
|
H6s5
|
H6t5
|
||||||||||
| H7 |
H7f6
|
H7g6
|
H7h6
|
H7js6
|
H7k6
|
H7m6
|
H7n6
|
H7p6
|
H7r6
|
H7s6
|
H7t6
|
H7u6
|
H7v6
|
H7x6
|
H7y6
|
H7z6
|
|||||
| H8 |
H8d8
|
H8e7
|
H8f7
|
H8g7
|
H8h7
|
H8js7
|
H8k7
|
H8m7
|
H8n7
|
H8p7
|
H8r7
|
H8s7
|
H8t7
|
H8u7
|
|||||||
| H9 |
H9c9
|
H9d9
|
H9e9
|
H9f9
|
H9h9
|
Note: • H6/h5 is a transition fit for sizes ≤ 3mm. • H8/r7 is a transition fit for sizes ≤ 100mm. • For common sizes (≤ 500mm), the Base Hole System is preferred: Hole machining is more complex, so minimizing the number of custom tools and gauges is highly recommended. • Fits between bearings (including linear bearings) and shafts use the Base Hole System to avoid secondary machining of standard commercial parts. |
|||||||||||||||
| H10 |
H10c10
|
H10d10
|
H10h10
|
||||||||||||||||||
| H11 |
H11a11
|
H11b11
|
H11c11
|
H11d11
|
H11h11
|
||||||||||||||||
| H12 |
H12h12
|
||||||||||||||||||||
1.5 Base Shaft System Fits
| Hole Shaft | Clearance Fits | Transition Fits | Interference Fits | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| A | B | C | D | E | F | G | H | JS | K | M | N | P | R | S | T | U | |
| h5 |
F6h5
|
G6h5
|
H6h5
|
JS6h5
|
K6h5
|
M6h5
|
N6h5
|
P6h5
|
R6h5
|
S6h5
|
T6h5
|
||||||
| h6 |
E8h6
|
F7h6
|
G7h6
|
H7h6
|
JS7h6
|
K7h6
|
M7h6
|
N7h6
|
P7h6
|
R7h6
|
S7h6
|
T7h6
|
U7h6
|
||||
| h7 |
E8h7
|
F8h7
|
G8h7
|
H8h7
|
JS8h7
|
K8h7
|
M8h7
|
N8h7
|
Note: • The Base Shaft System is preferred when lower tolerance grades (below IT8) are used. • For precision parts with dimensions < 1mm, the Base Shaft System is preferred (machining extremely thin shafts is difficult). • When multiple different fits occur on the same nominal size, the Base Shaft System is preferred. • Example: A piston pin has multiple fits on the same size, including: 1. Interference fit with piston (N6/h5) 2. Clearance fit with connecting rod (G6/h5) In this case, machining the shaft (pin) to a uniform h5 size is the most economical approach. |
||||||||
| h8 |
D8h8
|
E8h8
|
F8h8
|
H8h8
|
|||||||||||||
| h9 |
D9h9
|
E9h9
|
F9h9
|
H9h9
|
|||||||||||||
| h10 |
D10h10
|
H10h10
|
|||||||||||||||
| h11 |
A11h11
|
B11h11
|
C11h11
|
D11h11
|
H11h11
|
||||||||||||
Pro Tip: How to Calculate Limits, Clearances & Determine Fit Types
1. Basic Tolerance Calculation
Tolerance is always a positive value.
• Hole Tolerance = Hole Upper Limit - Hole Lower Limit
• Shaft Tolerance = Shaft Upper Limit - Shaft Lower Limit
2. Maximum & Minimum Gaps
• Max Clearance (or Min Interference) =
Hole Upper Limit - Shaft Lower Limit
• Min Clearance (or Max Interference) =
Hole Lower Limit - Shaft Upper Limit
* Positive result = Gap (Clearance). Negative result = Interference.
3. How to Determine the Fit Type
- Clearance Fit: Both calculated results are Positive (or Min is 0). There is always a gap.
- Interference Fit: Both calculated results are Negative. Parts must be pressed/shrunk together.
- Transition Fit: One result is Positive, the other is Negative. Depending on actual machining, it could be a slight gap or a slight press.
2. General Tolerances for Linear Dimensions (GB/T 1804-2000) - Unit: mm
Application: Standard machined dimensions without specified tolerances. Technical requirement usually states: General tolerances per GB/T 1804-m.
| Tolerance Grade | 0.5 ~ 3 | >3 ~ 6 | >6 ~ 30 | >30 ~ 120 | >120 ~ 400 | >400 ~ 1000 | >1000 ~ 2000 | >2000 ~ 4000 |
|---|---|---|---|---|---|---|---|---|
| Fine (f) | ±0.05 | ±0.05 | ±0.1 | ±0.15 | ±0.2 | ±0.3 | ±0.5 | - |
| Medium (m) (Default) | ±0.1 | ±0.1 | ±0.2 | ±0.3 | ±0.5 | ±0.8 | ±1.2 | ±2 |
| Coarse (c) (Unmachined/Holes) | ±0.2 | ±0.3 | ±0.5 | ±0.8 | ±1.2 | ±2.0 | ±3.0 | ±4.0 |
3. General Geometrical Tolerances (GB/T 1184-1996) - Unit: mm
Application: Areas without feature control frames default to this table. Technical requirement usually states: General geometrical tolerances per GB/T 1184-K.
3.1 Straightness & Flatness (e.g., flange backs/non-sealing faces)
| Tolerance Grade | ≤10 | >10 ~ 30 | >30 ~ 100 | >100 ~ 300 | >300 ~ 1000 | >1000 ~ 3000 |
|---|---|---|---|---|---|---|
| H (Strict) | 0.02 | 0.05 | 0.1 | 0.2 | 0.3 | 0.4 |
| K (Default) | 0.05 | 0.1 | 0.2 | 0.4 | 0.6 | 0.8 |
3.2 Perpendicularity (e.g., top flange to main bore) & Symmetry
| Tolerance Grade | ≤100 | >100 ~ 300 | >300 ~ 1000 | >1000 ~ 3000 |
|---|---|---|---|---|
| H (Strict) | 0.2 | 0.3 | 0.4 | 0.5 |
| K (Default) | 0.4 / (Sym. 0.6) | 0.6 / (Sym. 0.6) | 0.8 / (Sym. 0.8) | 1.0 / (Sym. 1.0) |
3.3 Coaxiality & Circular Run-out (e.g., non-core counterbores)
| Tolerance Grade | Class H | Class K (Default) | Class L |
|---|---|---|---|
| General Run-out / Coaxiality (All sizes) | 0.1 mm | 0.2 mm | 0.5 mm |
4. Specified Geometrical Tolerances (GB/T 1184 App. B) - Converted to mm
Application: Lookup values for feature control frames (e.g., ◎|0.05|A). Original values in μm have been divided by 1000 and converted to mm. Valves typically use Grade 7 (Precision) or Grade 8 (Standard).
Table B1: Straightness & Flatness
| Basic Length L (mm) |
Tolerance Grade (mm) | |||
|---|---|---|---|---|
| Grade 6 | Grade 7 | Grade 8 | Grade 9 | |
| ≤10 | 0.003 | 0.005 | 0.008 | 0.012 |
| >10~16 | 0.004 | 0.006 | 0.010 | 0.015 |
| >16~25 | 0.005 | 0.008 | 0.012 | 0.020 |
| >25~40 | 0.006 | 0.010 | 0.015 | 0.025 |
| >40~63 | 0.008 | 0.012 | 0.020 | 0.030 |
| >63~100 | 0.010 | 0.015 | 0.025 | 0.040 |
| >100~160 | 0.012 | 0.020 | 0.030 | 0.050 |
| >160~250 | 0.015 | 0.025 | 0.040 | 0.060 |
| >250~400 | 0.020 | 0.030 | 0.050 | 0.080 |
| >400~630 | 0.025 | 0.040 | 0.060 | 0.100 |
| >630~1000 | 0.030 | 0.050 | 0.080 | 0.120 |
| >1000~1600 | 0.040 | 0.060 | 0.100 | 0.150 |
| >1600~2500 | 0.050 | 0.080 | 0.120 | 0.200 |
Table B2: Roundness & Cylindricity
| Basic Dia. d(D) (mm) |
Tolerance Grade (mm) | |||
|---|---|---|---|---|
| Grade 6 | Grade 7 | Grade 8 | Grade 9 | |
| ≤3 | 0.002 | 0.003 | 0.004 | 0.006 |
| >3~6 | 0.0025 | 0.004 | 0.005 | 0.008 |
| >6~10 | 0.0025 | 0.004 | 0.006 | 0.009 |
| >10~18 | 0.003 | 0.005 | 0.008 | 0.011 |
| >18~30 | 0.004 | 0.006 | 0.009 | 0.013 |
| >30~50 | 0.004 | 0.007 | 0.011 | 0.016 |
| >50~80 | 0.005 | 0.008 | 0.013 | 0.019 |
| >80~120 | 0.006 | 0.010 | 0.015 | 0.022 |
| >120~180 | 0.008 | 0.012 | 0.018 | 0.025 |
| >180~250 | 0.010 | 0.014 | 0.020 | 0.029 |
| >250~315 | 0.012 | 0.016 | 0.023 | 0.032 |
| >315~400 | 0.013 | 0.018 | 0.025 | 0.036 |
| >400~500 | 0.015 | 0.020 | 0.027 | 0.040 |
Table B3: Parallelism, Perpendicularity, Angularity
| Basic Dim L,d(D) (mm) |
Tolerance Grade (mm) | |||
|---|---|---|---|---|
| Grade 6 | Grade 7 | Grade 8 | Grade 9 | |
| ≤10 | 0.008 | 0.012 | 0.020 | 0.030 |
| >10~16 | 0.010 | 0.015 | 0.025 | 0.040 |
| >16~25 | 0.012 | 0.020 | 0.030 | 0.050 |
| >25~40 | 0.015 | 0.025 | 0.040 | 0.060 |
| >40~63 | 0.020 | 0.030 | 0.050 | 0.080 |
| >63~100 | 0.025 | 0.040 | 0.060 | 0.100 |
| >100~160 | 0.030 | 0.050 | 0.080 | 0.120 |
| >160~250 | 0.040 | 0.060 | 0.100 | 0.150 |
| >250~400 | 0.050 | 0.080 | 0.120 | 0.200 |
| >400~630 | 0.060 | 0.100 | 0.150 | 0.250 |
| >630~1000 | 0.080 | 0.120 | 0.200 | 0.300 |
| >1000~1600 | 0.100 | 0.150 | 0.250 | 0.400 |
| >1600~2500 | 0.120 | 0.200 | 0.300 | 0.500 |
Table B4: Coaxiality, Symmetry, Run-out, etc.
| Basic Dim d(D),B,L (mm) |
Tolerance Grade (mm) | |||
|---|---|---|---|---|
| Grade 6 | Grade 7 | Grade 8 | Grade 9 | |
| >6~10 | 0.006 | 0.010 | 0.015 | 0.030 |
| >10~18 | 0.008 | 0.012 | 0.020 | 0.040 |
| >18~30 | 0.010 | 0.015 | 0.025 | 0.050 |
| >30~50 | 0.012 | 0.020 | 0.030 | 0.060 |
| >50~120 | 0.015 | 0.025 | 0.040 | 0.080 |
| >120~250 | 0.020 | 0.030 | 0.050 | 0.100 |
| >250~500 | 0.025 | 0.040 | 0.060 | 0.120 |
| >500~800 | 0.030 | 0.050 | 0.080 | 0.150 |
| >800~1250 | 0.040 | 0.060 | 0.100 | 0.200 |
| >1250~2000 | 0.050 | 0.080 | 0.120 | 0.250 |
| >2000~3150 | 0.060 | 0.100 | 0.150 | 0.300 |
| >3150~5000 | 0.080 | 0.120 | 0.200 | 0.400 |
| >5000~8000 | 0.100 | 0.150 | 0.250 | 0.500 |
5. Surface Roughness Ra Selection Guide (GB/T 1031-2009)
Application: Drawing roughness callouts. When told to "use your best judgment", apply these empirical values (Series 1 preferred).
| Standard Ra (μm) (Preferred Series 1, GB/T 1031) |
Old Std (Equivalent) |
Common Valve Machining Applications (Direct Reference) |
|---|---|---|
| Ra 25 ~ 50 | ▽ 1 ~ ▽ 2 | Rough machining, flame cut edges, non-contact internal body surfaces. |
| Ra 12.5 (Most Common) | ▽ 3 | Rough machined surfaces. e.g., Flange backs (non-sealing), valve body OD, standard steps, drilled bolt holes. |
| Ra 6.3 | ▽ 4 | General mating surfaces. e.g., Bracket connections, non-sliding locating holes, Flange Raised Faces (RF) with serrated finish. |
| Ra 3.2 (Important Fit) | ▽ 5 | Relative motion surfaces. e.g., Stem to bushing fits, stuffing box (packing) inner walls, cylinder bores. |
| Ra 1.6 (Core Sealing) | ▽ 6 | Absolute sealing surfaces. e.g., Knife gate plates (both sides), metal body contact faces for soft-seated butterfly valves, standard valve stems. |
| Ra 0.8 | ▽ 7 | High-precision sliding. e.g., Spools in control valves, precision polished stems for special packing. |
| Ra 0.4 ~ 0.2 | ▽ 8 ~ ▽ 9 | Metal-to-Metal Hard Sealing. e.g., Tungsten carbide coated ball valve spheres, precision lapped gate valve seats. |
6.L: Valve Face-to-Face Dimensions & Tolerances (GB/T 12221-2005)
Standard Update Notice: The new standard GB/T 12221-2025 has just been released to replace the 2005 version. Due to copyright restrictions on the newly published document, the data below currently reflects the widely-used GB/T 12221-2005. Please consult the official 2025 document for absolute compliance on new projects.Application: The overall thickness (L) between two connecting faces when 3D modeling. This is a critical parameter for customer selection. Bold values are preferred dimensions.
Table 21: Flanged Valve Face-to-Face Tolerance (Unit: mm)
| Face-to-Face L | Limit Deviation |
|---|---|
| ≤250 | ±2 |
| >250～500 | ±3 |
| >500～800 | ±4 |
| >800～1000 | ±5 |
| >1000～1600 | ±6 |
| >1600～2250 | ±8 |
| ≥2250 | ±10 |
Table 8: Wafer Knife Gate Valve Face-to-Face (Unit: mm)
Note: Limit deviation for knife gate valves is a fixed ±1.6mm.
| Nominal Dia (DN) | Nominal Pressure PN ≤ 2.0 MPa (Face-to-Face) | ||
|---|---|---|---|
| Basic Series J16 | Basic Series J17 | Basic Series J18 | |
| 50 | 48 | 40 | 40 |
| 65 | — | 40 | 40 |
| 80 | 51 | 50 | 50 |
| 100 | 51 | 50 | 50 |
| 125 | 57 | 50 | 50 |
| 150 | 57 | 60 | 60 |
| 200 | 70 | 60 | 60 |
| 250 | 70 | 70 | 70 |
| 300 | 76 | 70 | 80 |
| 350 | 76 | 80 | 92 |
| 400 | 89 | 80 | 120 |
| 450 | 89 | 90 | 120 |
| 500 | 114 | 90 | 132 |
| 600 | 114 | 100 | 132 |
Table 10: Butterfly Valve & Butterfly Check Valve Face-to-Face (Unit: mm)
| Nominal Dia DN |
Double Flanged Face-to-Face | Wafer Type Face-to-Face | ||||
|---|---|---|---|---|---|---|
| Nominal Pressure PN / MPa | ≤2.5 | ≤4.0 | ||||
| ≤2.0 (Short) | ≤2.5 (Long) | Short (J1) | Medium (J2) | Long (J3) | J2 / J4 | |
| 40 | 106 | 140 | 33 | — | 33 | — |
| 50 | 108 | 150 | 43 | — | 43 | — |
| 65 | 112 | 170 | 46 | — | 46 | — |
| 80 | 114 | 180 | 46 | 49 | 64 | 49 |
| 100 | 127 | 190 | 52 | 56 | 64 | 56 |
| 125 | 140 | 200 | 56 | 64 | 70 | 64 |
| 150 | 140 | 210 | 56 | 70 | 76 | 70 |
| 200 | 152 | 230 | 60 | 71 | 89 | 71 |
| 250 | 165 | 250 | 68 | 76 | 114 | 76 |
| 300 | 178 | 270 | 78 | 83 | 114 | 83 |
| 350 | 190 | 290 | 78 | 92 | 127 | 127 |
| 400 | 216 | 310 | 102 | 102 | 140 | 140 |
| 450 | 222 | 330 | 114 | 114 | 152 | 160 |
| 500 | 229 | 350 | 127 | 127 | 152 | 170 |
| 550 | — | — | 154 | — | — | — |
| 600 | 267 | 390 | 154 | 154 | 178 | 200 |
| 650 | — | — | 165 | — | — | — |
| 700 | 292 | 430 | 165 | — | 229 | — |
| 750 | — | — | 190 | — | — | — |
| 800 | 318 | 470 | 190 | — | 241 | — |
| 900 | 330 | 510 | 203 | 200 | 241 | — |
| 1000 | 410 | 550 | 216 | — | 300 | — |
| 1200 | 470 | 630 | 254 | 276 | 360 | — |
| 1400 | 530 | 710 | 279 | — | 390 | — |
| 1600 | 600 | 790 | 318 | — | 440 | — |
| 1800 | 670 | 870 | 356 | — | 490 | — |
| 2000 | 760 | 950 | 406 | — | 540 | — |
| 2200 | 800 | 1000 | — | — | 590 | — |
| 2400 | 850 | 1100 | — | — | 650 | — |
| 2600 | 900 | 1200 | — | — | 700 | — |
| 2800 | 950 | 1300 | — | — | 760 | — |
| 3000 | 1000 | 1400 | — | — | 810 | — |
| 3200 | 1100 | — | — | — | 870 | — |
| 3400 | 1200 | — | — | — | — | — |
| 3600 | 1200 | — | — | — | — | — |
| 3800 | 1200 | — | — | — | — | — |
| 4000 | 1300 | — | — | — | — | — |
| Basic Series | 13 | 14 | J1 | J2 | J3 | J2/J4 |
Table of Contents
0. Latest Standards Update 1. IT Grades & Hole/Shaft Fits - 1.1 IT Values Reference - 1.2 Hole Deviations (A-M) - 1.3 Shaft Deviations (a-j) - 1.4 Base Hole Fits - 1.5 Base Shaft Fits ↳ Pro Tip: Fit Calculations 2. General Linear Tolerances 3. General Geometric Tolerances 4. Specified Geometric Tolerances 5. Surface Roughness (Ra) 6. Valve Face-to-Face (L)
