BRITISH & METRIC FLUID CONVEYING PRODUCTS

Tips to Identifying Threads
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Using the thread identification kit from Malone Specialty Inc. or a commercially available caliper, thread gauge and thread pitch gauge, you will be able to identify the following thread forms.

American Dyseal Pipe Threads

  • SAE J476a, NPT, NPSM
  • American National Screw Threads
  • SAE J475a, JIC
  • British Pipe Parallel Threads
  • ISO/BS 2779-NF EO3-005 DIN 3852 Pg. 2 (Parallel Threads)
  • British Pipe Taper Threads
  • BS21-IS07, DIN 3852 (Taper Threads)
  • Metric Parallel Threads
  • ISO 6149 DIN 3852
  • Metric Taper Threads
  • DIN 3852
  • Japanese Industrial Standard
  • JIS BO202 (PF Thread), BO203 Tapered (PT Thread)

The calipers in the kit can be used to help you identify both American and Foreign thread forms, including internal and external threads.
The top scale is used to identify all inch threads and the bottom scale is used to identify all metric threads. When using the scale to correctly determine your thread size, use the first, or left, line in the window area. See Figure 1 below for clarification.

figure1

To identify external or male threads, use the bottom jaws of the caliper and to identify internal or female threads use the top jaws of the caliper. See Figure 1 above for clarification.

All thread pitch gauges in the kit are used the same way in identifying internal or external threads. Each leaf has a number on it telling you how many threads per inch you have. The only exception to this is on the metric gauge. On the metric gauge, the number on each leaf represents the thread pitch (distance from the crest of one thread to the crest of the next thread.) in millimeters. Figure 2 below shows you the proper use of the thread gauge.

figure2

One important point illustrated above is the use of the correct thread pitch gauge on the threads. Incorrect thread identification can cause: equipment failure, leaking connections, thread damage to mating parts, or possible serious human injury.Additional thread identification is explained throughout this catalog.

General Information

In identifying fittings, you should always be sure to identify both sides of the fitting. Except for plugs, caps and unions, all fittings grip a rigid tube or a hose and are screwed into some type of port. Try to divide each fitting into two separate identifying sections – side A (grips tube or hose) and side B (the port threads).

tech_fig_3

Identifying the Port Side of Fittings (Side B)

There are six common port threads on fittings. They are as follows:

1. British Parallel Pipe Threads
2. British Taper Pipe Threads
3. Metric Threads, Parallel
4. Metric Threads, Taper
5. NPT
6. SAE Straight Threads

Parallel Thread vs. Tapered Threads

To identify any port side thread, first determine if the thread is tapered or parallel by inspection and/or use of a straight edge. A parallel thread will have some means of sealing at the top of the thread, either by O-ring, metal seal, or possibly by a machined ring in the hex itself. A taper thread seals on the threads themselves by wedging into the female port and sealing by thread contact.

figure4

figure5

There are various American Pipe Thread series in use today. Two of the more popular thread forms used are the Dryseal American Standard Taper Pipe Thread (NPTF) and American Standard Straight Pipe Thread for Mechanical Joints (NPSM). Unlike the British threads, our pipe threads have a 60º thread flank angle. See Figure 6. (Refer to Chart #3 for additional information.)

figure6

Two of the more popular thread forms used in the world today are the British Standard Pipe Tapered (BSPT) and the British Standard Parallel Pipe (BSPP). Both of these thread forms have a 55º thread flank angle. See Figure 7. The BSPT or BSPP cannot be interchanged with our own pipe threads due to the difference in thread flank angle.
The British thread forms use sizes similar to our own pipe threads – 1/8, 1/4, 3/8, 1/2, etc. First, determine if the thread is tapered or parallel, then measure it with the thread gauges supplied in your Thread ID Kit under British thread forms. All BSPT and BSPP sizes can be compared to our own NPT for sizing. (A 1/4″ BSPT or BSPP thread, if held end to end with a 1/4″ NPT will have approximately the same thread O.D.) Refer to Chart #2 for additional information.

Neither the British Standard Parallel Pipe or the British Standard Pipe Tapered are true metric threads, although many people find these threads “foreign” and conclude that they must then be "metric".

figure7

The Japanese Industrial Standard (J.I.S.) tapered and parallel threads are the same as the British Standard Pipe Tapered and British Standard Parallel Pipe threads. In addition to normal BSPP hose fittings, there are also flare fittings with a 30º or 45º flare in combination with either metric or BSPP threads that meet the J.I.S. standard. These are commonly called Komatsu and Mitsubishi fittings.

Another port thread form found on overseas equipment is the true metric thread. This thread form is probably the easiest to measure and identify.
First, determine if your thread is tapered or parallel by the same methods employed under the British Threads Forms Instructions. If you believe you have a metric parallel thread, you can measure it as follows:
First, measure the outer diameter of the thread in millimeters as shown in the following diagram using your calipers. (D = 24mm). Next, use your metric thread gauges to measure the distance from the crest of one thread to the crest of the next in millimeters. (P)

figure8

This thread has 1.5 millimeters between threads. Combine the O.D. of the thread measurement with this second measurement to form a metric thread callout (i.e. M24 x 1.5).

To measure metric taper threads, follow the same instructions as for the metric parallel thread. Since it will be difficult to measure the O.D. of a tapered thread, measure the O.D. at the third thread from the end. Then use your metric thread gauges as before. The thread callout will be M24 x 1.5 tapered. Information on additional thread identification is shown in Chart #1.

Identifying the Port Side of Fittings (Side B)

To identify any port side thread, first determine if the thread is tapered or parallel by inspection and/or use of a straight edge. A parallel thread will have some means of sealing at the top of the thread, either by O-ring, metal seal, or possibly by a machined ring in the hex itself. A taper thread seals on the threads themselves by wedging into the female port and sealing by thread contact.
figure4
To identify any port side thread, first determine if the thread is tapered or parallel by inspection and/or use of a straight edge. A parallel thread will have some means of sealing at the top of the thread, either by O-ring, metal seal, or possibly by a machined ring in the hex itself. A taper thread seals on the threads themselves by wedging into the female port and sealing by thread contact.
figure4
There are various American Pipe Thread series in use today. Two of the more popular thread forms used are the Dryseal American Standard Taper Pipe Thread (NPTF) and American Standard Straight Pipe Thread for Mechanical Joints (NPSM). Unlike the British threads, our pipe threads have a 60º thread flank angle. See Figure 6. (Refer to Chart #3 for additional information.)
figure6
Two of the more popular thread forms used in the world today are the British Standard Pipe Tapered (BSPT) and the British Standard Parallel Pipe (BSPP). Both of these thread forms have a 55º thread flank angle. See Figure 7. The BSPT or BSPP cannot be interchanged with our own pipe threads due to the difference in thread flank angle.
The British thread forms use sizes similar to our own pipe threads – 1/8, 1/4, 3/8, 1/2, etc. First, determine if the thread is tapered or parallel, then measure it with the thread gauges supplied in your Thread ID Kit under British thread forms. All BSPT and BSPP sizes can be compared to our own NPT for sizing. (A 1/4″ BSPT or BSPP thread, if held end to end with a 1/4″ NPT will have approximately the same thread O.D.) Refer to Chart #2 for additional information. Neither the British Standard Parallel Pipe or the British Standard Pipe Tapered are true metric threads, although many people find these threads “foreign” and conclude that they must then be "metric".
figure7
The Japanese Industrial Standard (J.I.S.) tapered and parallel threads are the same as the British Standard Pipe Tapered and British Standard Parallel Pipe threads. In addition to normal BSPP hose fittings, there are also flare fittings with a 30º or 45º flare in combination with either metric or BSPP threads that meet the J.I.S. standard. These are commonly called Komatsu and Mitsubishi fittings.
Another port thread form found on overseas equipment is the true metric thread. This thread form is probably the easiest to measure and identify.
First, determine if your thread is tapered or parallel by the same methods employed under the British Threads Forms Instructions. If you believe you have a metric parallel thread, you can measure it as follows:
First, measure the outer diameter of the thread in millimeters as shown in the following diagram using your calipers. (D = 24mm). Next, use your metric thread gauges to measure the distance from the crest of one thread to the crest of the next in millimeters. (P) This thread has 1.5 millimeters between threads. Combine the O.D. of the thread measurement with this second measurement to form a metric thread callout (i.e. M24 x 1.5). To measure metric taper threads, follow the same instructions as for the metric parallel thread. Since it will be difficult to measure the O.D. of a tapered thread, measure the O.D. at the third thread from the end. Then use your metric thread gauges as before. The thread callout will be M24 x 1.5 tapered. Information on additional thread identification is shown in Chart #1.
figure8

Identifying the Tube (Side A) Side

Probably the single most popular bite-type fitting in Europe is the 24º cone. An EO style fitting and SAE flareless incorporates a 24º tapered throat angle and the nut drives the ferrule into the tube as it is tightened during assembly. There are various forms of ferrules that are used, but the bodies and nuts are all made to standards insuring the interchangeability between manufacturers. In metric sizes, the 24º fitting is made in six different series, AL series and LL series for low pressure, L series for medium pressure service, S series for high-pressure severe-service application, A series for French metric and AG series for GAZ.
To identify metric 24º fittings, first examine the markings on the tube nut itself. Most reputable manufacturers of metric 24º fittings mark the tube size and the series on the nose of the nut itself. See Figure #9.
figure9
Tube Connections The cross-section in Figure #10 represents one end of a flareless tube connection without the nut and sleeve. The thread size can easily be identified by measuring the dimensions as shown in Figure #8 and the connection tube size can easily be identified by measuring dimension A in Figure #10. Information on additional thread identification is shown in Chart #1.
figure10
The 37º flared fitting functions by establishing one circular line contact between the nose of the fitting and the flare of the tube or female seat in a hose fitting. The function of the threads is to hold the two mating threads mechanically in place. JIC 37º couplings are generally used with higher-pressure industrial and mobile applications. Information on additional thread identification is shown in Chart #5.
Sealing characteristics and thread identification is the same as the JIC 37º flared fittings. SAE 45º couplings are generally used in automotive low-pressure systems. Information on additional thread identification is shown in Chart #8.
Straight thread adapters with O-ring into SAE Straight thread bosses seal strictly by use of the O-ring. Information on additional thread identification is shown in Chart #6.
The BSP and SAE Standard Flat face fittings have an O-ring groove in the male end. The thread form is shown in Chart #2 & Chart #7. The BSP version is used on Hiab cranes and loaders.
The SAE Standard flange face fittings are made in two styles. Code 61 and Code 62. Code 61 is rated at 3000 PSI and Code 62 is rated at 6000 PSI, in all sizes. Additional flange information is shown in Chart #12 (for Code 61) & Chart 13 (for Code 62). Poclain has their own unique style of flange fittings.
In the SAE standards the female pipe swivel and the male pipe ends are said to have a 30º seat. This angle is measured from the seat to the centerline. In Europe both the British and Metric versions are said to have a 60º Cone, where the total angle is measured. The U.S. Standard National Pipe Straight Mechanical (NPSM) female swivel mates with the NPTF male fitting. Note the male end must have the 30º seat to seal properly. Refer to Chart 1, Chart 2 & Chart 3 for additional information.
Many manufacturers in Europe and the U.S. manufacture their swivel fittings with a ball nose. This allows the same component to be used with more than one style male end. (i.e. M12x1.5 nut on a ball nose swivel might fit both a 6mm Din 20078 24º Light Cone male and a 4mm Din 7631 60º Cone Male.) See Chart #1 for additional information.
These fittings have a metric tube stub, which will accept an EO nut and ferrule. When the ferrule is preset on the standpipe they function the same as the DIN swivels in the 24º cone paragraph.
Virtually all hydraulic and push-on hoses correspond in size to U.S. Standards. The size may be called out using the actual inside diameter in millimeters or a nominal diameter abbreviated “NW”, newnweite or “DN”. See chart #9 for all hose dimensions except 100R5, see Chart #10 for 100R5 hose. For PTFE hose dimensions see Chart #11.