شرح أحجام تجهيزات الأنابيب النحاسية: المواضيع, الأبعاد ودليل الاختيار

إن اختيار التركيب النحاسي المناسب ليس بهذه البساطة مثل مطابقة رقمين. تم وضع علامة مناسبة 1/2 بوصة does not necessarily have a 1/2-inch thread diameter, and a fitting with a similar measured diameter may still use a completely different thread standard.

فهم brass pipe fittings sizes, thread dimensions, nominal pipe size, and thread standards is essential when selecting brass elbows, المحملات, وصلات, محولات, hose connectors, and other threaded fittings.

This guide explains the most common brass fitting sizes, NPT and BSP threads, how to measure a brass fitting, and how to specify the correct size when ordering.

Brass Pipe Fitting

What Does “Brass Pipe Fitting Size” Actually Mean?

When suppliers or buyers refer to a brass fitting size, they are usually referring to the nominal connection size, not the actual physical diameter of the fitting.

Several different measurements may be involved:

Measurement	What It Means
الحجم الاسمي	Standardized size designation, such as 1/2″ أو 1″
الأنابيب التطوير التنظيمي	Actual outside diameter of the pipe
Thread Major Diameter	Largest diameter across an external thread
Thread Minor Diameter	Smallest diameter of the thread profile
Thread Pitch	Distance between adjacent threads
TPI	Threads per inch
Fitting Body OD	Outside diameter of the fitting body

على سبيل المثال, أ 1/2″ NPT brass fitting has a nominal size of 1/2 بوصة, but its external thread major diameter is approximately 0.840 بوصة (21.34 مم).

This is why simply measuring a fitting with a caliper is not enough to identify its size.

Nominal Size vs. Actual Diameter

The nominal size is a standardized designation used to describe the pipe or connection. It should not automatically be interpreted as the actual thread diameter or pipe outside diameter.

For accurate identification, check the following together:

• Nominal fitting size
• Thread standard
• Male or female thread
• Thread major or internal diameter
• TPI or thread pitch
• Thread profile

مهم: The dimensions in the following tables are standard reference dimensions for thread identification. Actual product dimensions can vary according to the applicable standard, tolerance, fitting design, والشركة المصنعة.

Nominal Size vs. Actual Diameter

Brass Pipe Fitting Size Chart

The most common brass pipe fittings are available in sizes ranging from small plumbing connections to larger industrial piping systems.

The following table provides common reference sizes for BSP threads:

الحجم الاسمي	BSP Thread Major Diameter	TPI
1/8″	9.728 مم	28
1/4″	13.157 مم	19
3/8″	16.662 مم	19
1/2″	20.955 مم	14
3/4″	26.441 مم	14
1″	33.249 مم	11
1-1/4″	41.910 مم	11
1-1/2″	47.803 مم	11
2″	59.614 مم	11

These dimensions refer to the thread, not the overall outside diameter of the brass fitting.

على سبيل المثال, a 1/2″ BSP threaded fitting has a thread major diameter of about 20.955 مم. The body of the elbow, قمزة, or coupling will normally be larger.

Common Brass Fitting Sizes

For plumbing, التدفئة والتهوية وتكييف الهواء, ماء, غاز, and general industrial applications, commonly requested brass fitting sizes include:

• 1/8″
• 1/4″
• 3/8″
• 1/2″
• 3/4″
• 1″
• 1-1/4″
• 1-1/2″
• 2″

Smaller sizes are common in instrumentation, small water lines, and hose connections, while larger sizes are frequently used in industrial and commercial piping.

1/2″ تركيب النحاس

NPT Brass Fitting Sizes

معاهدة حظر الانتشار النووي (تفتق الأنابيب الوطنية) is one of the most widely used inch-based pipe thread standards, particularly in North America.

NPT threads are tapered and use a 60-degree thread form. The thread dimensions are standardized under أسم B1.20.1.

A typical NPT brass fitting size chart is:

Nominal NPT Size	Approx. External Thread Diameter	TPI
1/8″	0.405″ (10.29 مم)	27
1/4″	0.540″ (13.72 مم)	18
3/8″	0.675″ (17.15 مم)	18
1/2″	0.840″ (21.34 مم)	14
3/4″	1.050″ (26.67 مم)	14
1″	1.315″ (33.40 مم)	11.5
1-1/4″	1.660″ (42.16 مم)	11.5
1-1/2″	1.900″ (48.26 مم)	11.5
2″	2.375″ (60.33 مم)	11.5

هذه هي thread reference dimensions, not the overall dimensions of the fitting.

على سبيل المثال, if you measure approximately 21.3 mm across the external thread of a fitting, it may be a 1/2″ NPT thread. لكن, diameter alone does not prove that identification. TPI and thread profile should also be checked.

Why NPT Size Can Be Confusing

A common mistake is assuming:

1/2″ NPT = 1/2″ thread diameter

It does not.

The 1/2″ designation refers to the nominal pipe size, while the external thread diameter is approximately 0.840 بوصة.

This difference is normal for pipe thread sizing and is one of the main reasons buyers should specify the complete thread standard when ordering brass fittings.

NPT Brass Fitting Sizes

BSP Brass Fitting Sizes

بي إس بي بي (Parallel) وBSPT (Tapered)

BSP—British Standard Pipe—is the dominant thread family in the UK, Europe, and many Commonwealth markets. Unlike NPT, BSP comes in two distinct forms:

بي إس بي بي (G thread, ايزو 228-1): Parallel threads. They do not seal on the threads themselves. A separate sealing surface—usually a bonded washer, O-ring, or gasket—provides the seal.

بي إس بي تي (R/Rp thread, ايزو 7-1): Tapered threads. Like NPT, BSPT seals by thread compression. لكن, the thread angle is 55 درجات (Whitworth form), not 60 درجات.

Common BSP Sizes

BSP Size	Approx. Major OD	TPI
1/8″	9.728 مم	28
1/4″	13.157 مم	19
3/8″	16.662 مم	19
1/2″	20.955 مم	14
3/4″	26.441 مم	14
1″	33.249 مم	11
1-1/4″	41.910 مم	11
1-1/2″	47.803 مم	11
2″	59.614 مم	11

Thread dimensions per ISO 228-1 (بي إس بي بي) و ايزو 7-1 (بي إس بي تي). Thread angle: 55° (Whitworth form). BSPP is parallel; BSPT is tapered at 1:16.

A common field observation: A thread measuring roughly 1/2 بوصة (12.7 مم) across the outside is likely a1/4″ BSP thread, not a 1/2″ بسب. The 1/2″ BSP thread actually measures20.955 مم across its major diameter. This “quarter-inch larger” rule of thumb holds approximately for BSP sizes up to about 1″, but always verify with a thread gauge rather than relying on visual estimation alone.

BSP Brass Fitting Sizes

NPT vs BSP: Why the Same Size May Not Fit

This is not a deep comparison—there is a dedicated article coming on that topic. But you need to know the essentials:

ميزة	معاهدة حظر الانتشار النووي	بسب
Primary Market	North America	المملكة المتحدة, Europe, Commonwealth
Thread Angle	60°	55°
Common Types	معاهدة حظر الانتشار النووي (مدبب)	بي إس بي بي (موازي), بي إس بي تي (مدبب)
Seal Method	Thread compression + sealant	بي إس بي بي: gasket/washer; بي إس بي تي: thread compression
Interchangeable?	لا	لا

Never specify a brass fitting only as “1/2 inch.” Always confirm the thread standard.

Even when nominal sizes match—for example, both are labeled 1/2″—NPT (60° thread angle) and BSP (55° Whitworth) will not thread together properly. The 5° angle difference causes cross-threading and guarantees leaks. Forcing them together damages both threads.

How to Measure a Brass Pipe Fitting

When you have an unmarked fitting in hand, five measurements will identify it:

خطوة 1: Check the Fitting Type

Elbow, قمزة, اقتران, محول, or connector? The type tells you what the fitting does, but not its size.

خطوة 2: Measure the Thread Diameter

Use a vernier caliper. For male threads, measure across the outside diameter at the widest point. For female threads, measure the inside diameter.

خطوة 3: Count the Threads (TPI)

Use a thread pitch gauge or place a ruler along the thread and count how many complete threads fit within one inch. This is the TPI.

خطوة 4: Identify the Thread Profile

Tapered or parallel? NPT and BSPT taper; BSPP and metric threads are parallel. Roll the fitting on a flat surface—a tapered thread will wobble visibly.

خطوة 5: Check Male or Female

يكتب	وصف
ذكر	External thread
أنثى	Internal thread
Male × Male	External threads on both ends
Female × Female	Internal threads on both ends
Male × Female	Mixed thread ends

A thread identification kit containing pitch gauges, a caliper, and reference profiles is worth the investment if you regularly handle mixed-standard fittings.

Measure a Brass Pipe Fitting

How to Choose the Right Brass Fitting Size

Once you understand what the size number actually means, selection becomes systematic. Run through these seven checks before placing an order:

Check	Question to Ask
Pipe Size	What is the pipe nominal size?
Thread Standard	معاهدة حظر الانتشار النووي, بي إس بي بي, بي إس بي تي, or metric?
اتصال	Male or female?
ضغط	What working pressure is required?
درجة حرارة	What operating temperature?
طلب	ماء, التدفئة والتهوية وتكييف الهواء, غاز, or industrial fluid?
مادة	What brass grade is required?

Common brass grades for fittings include CW617N (CuZn40Pb2) for general-purpose plumbing and CW602N (CuZn36Pb2As) for dezincification-resistant applications in aggressive water conditions.

Brass Fittings in industrial applications

Common Mistakes When Choosing Brass Fitting Sizes

خطأ 1: Treating Nominal Size as Actual Diameter

A 1/2″ fitting does not necessarily have a 1/2-inch thread diameter.

خطأ 2: Measuring Only the Fitting Body

The body diameter does not identify the thread size.

خطأ 3: Ignoring NPT vs. بسب

A similar diameter does not mean the threads are compatible.

خطأ 4: Confusing BSPP and BSPT

Both belong to the BSP family, but one is parallel and the other is tapered.

خطأ 5: Ignoring Male/Female Configuration

A correct thread size is not enough if the connection gender is wrong.

خطأ 6: Selecting by Diameter Without Checking TPI

Two threads can have similar diameters but different pitches or TPI.

تركيب النحاس Size vs Pipe Size: Are They the Same?

No—and this is where the confusion peaks.

مواصفة	Refers To
Fitting nominal size	Standard connection size label
الأنابيب التطوير التنظيمي	Outside diameter of the pipe
Pipe ID	Inside diameter of the pipe
Thread OD	Actual measured thread diameter

A fitting marked 1/2″ does not have a 12.7 mm thread OD. In NPT, the 1/2″ size has a 0.840″ thread OD. In BSP, the 1/2″ size has a 20.955 mm major diameter. The nominal size is a matching reference, not a physical dimension.

Brass Fitting Size vs Pipe Size

Need تجهيزات الأنابيب النحاسية for Your Project?

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