进口NGT气瓶圆锥螺纹规

NPT-一般密封圆锥管螺纹，牙型角60°，锥度1:16
NGT-美国气瓶圆锥螺纹，牙型角60°，锥度1:16，这个好像只有右旋

NGT vs. NPT

NGT = National Gas Taper per ANSI CGA V-1 Specification
NPT = National Pipe Taper per ANSI B1.20.1 Specification

Both NGT and NPT pipe screw thread forms have many similarities.

They have the same:
Lead 
Pitch
Taper
Flank Angles
E0 Pitch Diameter 
E1 Pitch Diameter 
Major Diameter Truncation
Minor Diameter Truncation

The differences are:

1. The NPT screw thread connection is intended for transmission of non-hazardous substances, like water.

2. The NGT screw thread connection is intended for transmission of dangerous gases. Things that if leak cause death and destruction to the immediate area and maybe beyond. A mis-made NGT thread can be a product liability issue. If the thread that you made fails, you can be sure that the lawyers will be asking you to prove that you own the thread specification and that you used the fully battery of calibrated gauges on the parts as they were made.

3. The NGT is a longer screw thread than the NPT. The NGT minimum effective length is approximately 3 threads longer than the NPT.

4. The NGT screw thread has tighter control of the major and minor diameter truncations than the NPT.

5. The ANSI B1.20.1 Specification which defines the NPT screw thread only requires: 
NPT-L1 Taper Screw Thread Ring Gage
NPT-L1 Taper Screw Thread Plug Gage

NOTE: The NPT-L1 Basic-Step taper screw thread gauge members are very similar to the NGT-L1 Basic-Step taper screw thread gage members, but not interchangeable. The pitch diameters are the same, but the minor and major diameters have tolerance differences in a direction that may allow a NPT-L1 Basic-Step taper screw thread gauge members to be modified into a NGT-L1 Basic-Step taper screw thread gage members. This is why the price of the L1 Basic-Step taper screw thread gauge member may be less than the other members.

6. The ANSI CGA V-1 Specification defines a complicated screw thread measurement system. There are rumors in the industry that the standard is being rewritten to simplify the screw thread gauge system. Many companies have been using the following tapered screw thread gages with full success:
NGT-L1 Taper Screw Thread Ring Gage
NGT-L8 Taper Screw Thread Ring Gage
NGT Crest-Check 6-Step Taper Plain Ring Gage
NGT Root-Check 6-Step Taper Screw Thread Ring Gage
NGT-L1 3-Step Screw Thread Plug Gage
NGT-L9 3-Step Screw Thread Plug Gage
NGT Crest-Check 6-Step Taper Plain Plug Gage
NGT Root-Check 6-Step Taper Screw Thread Plug Gage

This screw thread gauge system requires 3-step L1, L8 and L9 taper screw thread gage members, but most gauge makers only offer Basic-Step members. The 3-Step L1 and L9 plug gauge members are readily available for an extra cost. The 3-Step L1 and L8 taper screw thread ring gages require special gauge blanks and thus usually are available only with extended lead-time and increased price.

This system requires the Root-Check and Crest-Check taper gage members to be made as 6-Step, which is the form that the gauges are quoted by default.

NGT = National Gas Taper per ANSI CGA V-1 Specification
NPT = National Pipe Taper per ANSI B1.20.1 Specification
NGO = National Gas Outlet
ANSI CGA V-1 Specification = CSA B96
ANSI CGA V-1 Specification formerly ANSI B57.1

 一、英制螺纹（螺纹牙型角55度）Thread of British standard ( Thread pitch shape angle 55°)

            BSW－－－－英国标准惠氏螺纹（粗牙）British Standard Whitworth Thread ( Coarse )

            BSF－－－－英国标准惠氏螺纹（细牙）British Standard Whitworth Thread ( Fine )

            G－－－－直管螺纹（外螺纹分A、B两面级、丝锥分G、G－D）Straight pipe thread ( Outside )

                      thread in A\B: taps in G、G－D )

            R－－－－锥管外螺纹（旧代号ZG;KG）Outside paper pipe thread ( Old thread code  ZG,KG )

            RC－－－－锥管内螺纹（旧代号ZG;KG）Inside taper pipe thread ( Old thread code ZG,KG )

            二、美制螺纹（螺纹牙型角60度）Thread of American standard ( Thread pitch shape angle 60°

            UNC－－－－统一制粗牙螺纹（代替NC）Unified coarse pitch thread ( Instead of NC )

            UNF－－－－统一制细牙螺纹（代替NF）Unified fine pitch thread ( Instead of NF )

            UNEF－－－－统一制超细牙螺纹Unified superfine pitch thread

            UN－－－－－统一制不变螺距螺纹Unified thread

            UNS－－－－统一制特殊螺纹Unified Special thread

            NB―――――美国标准锯齿螺纹American standard buttress threads

            NPT－－－－一般用途锥管螺纹（旧代号Z;K）Taper pipe thread for general purpose ( Old

                          thread code Z,K )

            NPSC－－－－管接头直管内螺纹Internal straight pipe thread for connection

            NPSM－－－－设备上自由配合，机械连接用直管螺纹Straight pipe thread for general purpose

            NPTF－－－－干密封锥管螺纹Dryseal taper pipe thread

            NPSF－－－－干密封燃油直管螺纹Dryseal straight pipe internal thread

            NGT－－－－气瓶用锥螺纹Special thread for gas cylinder

            三、米制螺纹Metric thread

            ZM－－－－－米制锥管螺纹 Metric taper pipe thread

            四、其它螺纹Other threads

            SM－－－－缝纫机螺纹Thread for sewing machine

            PZ－－－－气瓶用锥螺纹Special thread for gas cylinder

            5V1－20V1－气门芯螺纹5V1－20V1－Tyre valve thread

            螺纹代号说明示例：Explanation of thread code. e. g.

            1/4－20UNC

            1/4－公称直径1/4" nominal dia. 1/4"

            20－每寸20牙twenty teeth per inch

            UNC－美标统一制粗牙螺纹unified coarse pitch thread ( American standard