How to Identify BSPP Fittings: Thread Size Chart, Sealing Methods and Comparisons
To identify a BSPP fitting, confirm that the thread remains the same diameter from end to end. Measure the male thread outside diameter or female thread inside diameter, determine the number of threads per inch and compare those measurements with a BSPP thread-size chart.
Thread measurements identify only part of the connection. You must also inspect the fitting’s sealing surface because BSPP threads may be used with bonded seals, O-rings, soft washers or matching conical seats. Two fittings can have the same BSPP thread and still be incompatible if their sealing methods do not match.
Key Takeaways
- BSPP stands for British Standard Pipe Parallel.
- BSPP threads are straight rather than tapered.
- BSPP uses a 55-degree thread profile with rounded crests and roots.
- BSPP sizes are based on nominal pipe sizes, not actual thread diameter.
- BSPP is an inch-based thread standard, not a metric thread.
- The threads normally provide clamping force rather than creating the hydraulic seal.
- The fitting’s sealing method must be identified in addition to the thread size.
- A fitting that threads into a BSPP connection is not necessarily compatible with it.
Hydraulic Safety Warning: Shut down the equipment, support or lower suspended loads and relieve stored hydraulic pressure before disconnecting a fitting. Confirm that the system is fully depressurized before beginning an inspection. Incorrectly matched hydraulic components can leak or fail, causing equipment damage or personal injury.
BSPP Thread-Size Chart
A BSPP size is a nominal pipe designation. It does not represent the actual outside diameter of the thread.
For example, a G 1/2 BSPP male thread measures approximately 0.82 inch, or 20.8 millimeters, across the outside of the threads. It does not measure 1/2 inch.
| BSPP/G Size | Common Dash Size | Threads Per Inch | Pitch | Approximate Male Thread O.D. | Approximate Female Thread I.D. |
|---|---|---|---|---|---|
| G 1/8 | -02 | 28 | 0.907 mm | 0.38 in. / 9.6 mm | 0.34 in. / 8.6 mm |
| G 1/4 | -04 | 19 | 1.337 mm | 0.51 in. / 13.0 mm | 0.47 in. / 11.9 mm |
| G 3/8 | -06 | 19 | 1.337 mm | 0.65 in. / 16.5 mm | 0.60 in. / 15.2 mm |
| G 1/2 | -08 | 14 | 1.814 mm | 0.82 in. / 20.8 mm | 0.75 in. / 19.1 mm |
| G 5/8 | -10 | 14 | 1.814 mm | 0.90 in. / 22.8 mm | 0.82 in. / 20.8 mm |
| G 3/4 | -12 | 14 | 1.814 mm | 1.04 in. / 26.3 mm | 0.97 in. / 24.6 mm |
| G 1 | -16 | 11 | 2.309 mm | 1.30 in. / 33.1 mm | 1.21 in. / 30.7 mm |
| G 1-1/4 | -20 | 11 | 2.309 mm | 1.64 in. / 41.8 mm | 1.55 in. / 39.4 mm |
| G 1-1/2 | -24 | 11 | 2.309 mm | 1.88 in. / 47.7 mm | 1.79 in. / 45.5 mm |
| G 2 | -32 | 11 | 2.309 mm | 2.34 in. / 59.5 mm | 2.26 in. / 57.4 mm |
These measurements are identification references rather than manufacturing inspection tolerances. Actual readings may vary slightly because of thread tolerances, plating, wear, damage and caliper placement.
Confirm the diameter, pitch, parallel thread form and sealing style before selecting a replacement.
What Is a BSPP Fitting?
A BSPP fitting uses a cylindrical or parallel British Standard Pipe thread. Both the male and female threads remain essentially the same diameter throughout their threaded length.
BSPP threads are commonly designated with the letter G, such as:
- G 1/4
- G 3/8
- G 1/2
- G 3/4
- G 1
BSPP threads are commonly manufactured according to ISO 228-1. The threads mechanically hold the fitting components together, but they are not normally intended to create a pressure-tight seal on the threads themselves.
When a pressure-tight assembly is required, the connection typically seals with a washer, O-ring, bonded seal or matching seat located outside the threads.
Is BSPP the Same as G Thread?
In common hydraulic and industrial usage, G thread generally refers to a BSPP parallel thread.
You may encounter descriptions such as:
- G 1/2
- 1/2 BSPP
- 1/2-inch BSP parallel
- British parallel pipe thread
These descriptions may refer to the same basic thread form, but they do not automatically identify the complete connection. The fitting’s port design, seat, O-ring, washer or swivel configuration must still be verified.
Is BSPP a Metric Thread?
BSPP is not a metric thread.
BSPP uses inch-based nominal pipe sizes and threads per inch. However, technicians often measure the thread diameter in millimeters because digital calipers make metric readings easy to compare.
A G 1/2 BSPP fitting, for example, has an approximate male thread outside diameter of 20.8 millimeters. That does not make it an M20 or M21 metric thread. The BSPP thread has a different thread angle, pitch and profile from a metric connection.
What Does a BSPP Thread Look Like?
BSPP has four primary thread characteristics:
- A parallel or cylindrical profile
- A 55-degree included thread angle
- Pitch expressed as threads per inch
- Rounded crests and roots
By comparison, common NPT, SAE and metric threads generally use a 60-degree thread profile. That five-degree difference can be difficult to judge visually, so a thread gauge is more reliable than appearance alone.
Why the Nominal BSPP Size Does Not Match the Thread Diameter
BSPP sizes originated as nominal pipe-bore designations rather than direct measurements of the thread.
This means:
- G 1/4 does not measure 1/4 inch across the threads.
- G 1/2 does not measure 1/2 inch across the threads.
- G 1 does not measure exactly 1 inch across the threads.
The actual thread diameter is significantly larger than the nominal size. Attempting to identify BSPP by matching a caliper reading directly to the stated pipe size will result in the wrong fitting.
What Tools Do You Need to Identify a BSPP Fitting?
Use the following tools whenever possible:
- Digital or dial caliper
- Inch thread-pitch gauge
- 55-degree thread-form gauge
- Straightedge
- Seat-angle gauge
- Bright inspection light
- Lint-free cleaning cloth
- BSPP thread-size chart
- Known mating fitting or thread-identification kit
A caliper measures the thread diameter. A thread-pitch gauge identifies the number of threads per inch. A straightedge or two diameter measurements help determine whether the thread is parallel or tapered. A seat gauge helps identify the connection’s sealing method.
How to Identify a BSPP Fitting Step by Step
Step 1: Clean and Inspect the Connection
Remove dirt, oil, old sealing material and loose debris from the fitting.
Inspect for:
- A washer beneath the fitting shoulder
- An O-ring
- A metal retaining ring
- A conical nose
- An internal cone seat
- A flat sealing face
- Tapered threads
- Damaged or distorted threads
Do not assume that a fitting is BSPP simply because it came from imported equipment. European and Asian machinery may contain BSPP, BSPT, metric, JIS, DIN and other connection systems.
Step 2: Determine Whether the Thread Is Parallel or Tapered
A BSPP thread maintains approximately the same diameter throughout its threaded length. A BSPT or NPT male thread becomes progressively smaller toward the end.
To check the thread:
- Measure the diameter near the first complete thread.
- Measure it again near the fitting body.
- Compare the readings.
If the diameters are essentially the same, the fitting may have a parallel thread. If the diameter changes noticeably, it is likely tapered.
A visual inspection can provide an initial indication, but caliper measurements are more reliable.
Step 3: Determine Whether the Fitting Is Male or Female
A male fitting has external threads. A female fitting has internal threads.
For a male fitting, measure across the outside crests of the thread.
For a female fitting, measure the inside opening across the thread crests. Female measurements are generally less definitive, so they should always be combined with thread pitch and sealing-surface identification.
Step 4: Measure the Thread Diameter
Place the caliper squarely across the thread.
For a male fitting:
- Measure the largest outside diameter.
- Avoid visibly damaged or flattened threads.
- Do not include a flange, chamfer or unthreaded shoulder.
For a female fitting:
- Measure the smallest internal opening across the thread crests.
- Keep the caliper centered and perpendicular to the opening.
Compare the result with the BSPP chart, but do not make the final identification until the thread pitch has also been confirmed.
Step 5: Determine the Threads per Inch
Place an inch thread-pitch gauge against the threads.
The correct gauge leaf should:
- Fit completely into the thread grooves
- Align with several consecutive threads
- Show no visible gap when viewed against a light source
Common BSPP pitches include:
- 28 threads per inch for G 1/8
- 19 threads per inch for G 1/4 and G 3/8
- 14 threads per inch for G 1/2, G 5/8 and G 3/4
- 11 threads per inch for G 1 and larger common sizes
Manual thread counting can provide an estimate, but a pitch gauge is more accurate, especially when the threaded length is short.
Step 6: Confirm the 55-Degree Thread Profile
Use a 55-degree thread gauge when the fitting could be confused with NPT, SAE, UNF or metric threads.
BSPP has a 55-degree included angle and rounded root-and-crest geometry. Common metric and Unified threads typically have a 60-degree included angle.
Thread angle should support the diameter and pitch measurements. It should not replace them.
Step 7: Match the Diameter and Pitch to the BSPP Chart
A BSPP identification should match all of the following:
- Parallel thread
- Male or female configuration
- Approximate thread diameter
- Correct threads per inch
- A 55-degree thread profile
- Corresponding BSPP or G size
For example, an outside diameter of approximately 20.8 millimeters combined with 14 threads per inch indicates a probable G 1/2 BSPP male thread.
Step 8: Identify the Sealing Method
Do not stop after identifying the thread.
Inspect whether the connection seals with:
- A bonded washer
- An O-ring and retaining ring
- A soft flat washer
- A 60-degree included cone
- Another application-specific sealing arrangement
A matching BSPP thread does not guarantee that two fitting ends use compatible sealing surfaces.
Step 9: Identify the Opposite End
Many adapters use BSPP on only one end.
The opposite end may be:
- JIC
- NPT or NPTF
- BSPT
- SAE O-Ring Boss
- O-Ring Face Seal
- Metric
- DIN
- JIS
- Another BSPP size
- A hydraulic flange
Record the connection type and size of every fitting end before ordering a replacement.
How Do BSPP Fittings Seal?
BSPP threads typically hold the fitting in position and generate clamping force. The pressure seal usually occurs at a separate surface outside the threads.
The correct sealing method depends on the fitting and port design.
Bonded Seal or Dowty Washer
A bonded seal consists of a metal washer with an elastomeric sealing element bonded to its inner diameter.
The seal is installed beneath the male fitting’s shoulder. As the fitting is tightened, the seal is compressed between the fitting shoulder and the flat surface surrounding the female port.
The port should have a suitable flat or spot-faced sealing surface. Scratches, corrosion, casting irregularities or an uneven face can prevent the washer from sealing uniformly.
O-Ring and Retaining Ring
Some male BSPP port fittings use an O-ring supported by a metal retaining washer or ring.
The fitting seals when the O-ring is compressed against the flat surface surrounding the female port. The retaining element controls the O-ring position and helps prevent extrusion.
The replacement O-ring must be compatible with:
- Hydraulic fluid
- Operating temperature
- System pressure
- Fitting design
- Port geometry
A threaded connection that fits but lacks the required O-ring arrangement is not a complete or reliable seal.
Flat-Face Swivel With Soft Washer
Some BSPP male and female flat-face swivel connections use a soft sealing washer between the two mating faces.
The washer creates the pressure seal as the swivel nut draws the faces together. The exact fitting pressure rating and application should be verified before substitution.
BSPP 60-Degree Included Cone
Some BSPP hose and swivel fittings seal through matching conical surfaces.
This connection may be described as:
- A 60-degree included cone
- A 30-degree cone measured from the centerline
- A 30-degree seat
Those descriptions refer to the same basic geometry from different reference points.
A male fitting with a 30-degree chamfer can seal against a matching female swivel seat. The threads pull the two cone surfaces together, while the conical contact creates the pressure seal.
Metal-to-Metal Cone Seal
A metal cone connection depends on accurate contact between the male and female sealing surfaces.
Inspect for:
- Scratches
- Burrs
- Dents
- Corrosion
- Deformation
- Embedded debris
- Incorrect seat dimensions
More tightening will not repair damaged or incompatible cone surfaces.
BSPP Compared With Similar Hydraulic Threads
| Connection | Thread Profile | Parallel or Tapered | Primary Sealing Method | Key Identifier |
|---|---|---|---|---|
| BSPP | 55° | Parallel | Washer, O-ring or matching seat | Constant diameter; often marked G |
| BSPT | 55° | Tapered male | Thread interference | Diameter changes along male thread |
| NPT/NPTF | 60° | Tapered | Thread interference | Different angle and pitch series |
| Metric parallel | 60° | Parallel | Depends on connection design | Diameter and pitch specified in millimeters |
| SAE/UNF | 60° | Parallel | O-ring, flare or other external seal | Unified thread dimensions |
| JIS BSPP cone | 55° thread | Parallel | Conical seat | BSPP thread with Japanese-standard seat design |
BSPP Versus BSPT
BSPP and BSPT both use a 55-degree British thread profile, but BSPP is parallel and BSPT is tapered.
A male BSPT thread can sometimes enter a fixed female BSPP thread in a connection specifically designed to seal through the tapered male thread. This does not mean that all BSPP and BSPT fittings are interchangeable.
A BSPP male connection normally requires an external sealing method such as:
- A bonded washer
- An O-ring assembly
- A flat-face washer
- A matching conical seat
Do not assume compatibility merely because the threads engage. Confirm the fitting standard, port type and required sealing method.
BSPP Versus NPT
BSPP and NPT differ in thread form, taper and sealing method.
| Feature | BSPP | NPT |
|---|---|---|
| Thread shape | Parallel | Tapered |
| Included thread angle | 55° | 60° |
| Crest and root | Rounded | Flatter profile |
| Common pitch for 1/4 size | 19 TPI | 18 TPI |
| Common pitch for 3/8 size | 19 TPI | 18 TPI |
| Primary seal | External washer, O-ring or seat | Thread interference and sealant |
Some BSPP and NPT sizes are close enough that the connection may begin to thread together. That does not make them compatible.
The incorrect thread angle, taper or pitch can cause:
- Binding
- Cross-threading
- Damaged thread profiles
- Incomplete engagement
- Leakage
- Port damage
BSPP Versus Metric Threads
BSPP and metric threads may both be parallel, and certain diameters can appear similar when measured with a caliper.
The primary differences are:
- BSPP uses a 55-degree profile.
- Metric threads generally use a 60-degree profile.
- BSPP pitch is commonly expressed as threads per inch.
- Metric pitch is expressed as the distance between threads in millimeters.
- The sealing surfaces may also differ.
For example, a BSPP male with a 30-degree chamfer can resemble certain metric connections. Confirm the diameter, pitch, thread profile and sealing seat before deciding which system is present.
BSPP Versus SAE Straight Threads
Both BSPP and SAE connections may use parallel threads, but their thread profiles and dimensions are different.
SAE straight threads generally use a 60-degree Unified thread form. BSPP uses a 55-degree British profile.
SAE O-Ring Boss connections also seal with an O-ring, but the existence of an O-ring does not make an unknown connection ORB. The thread diameter, pitch and port geometry must match the SAE standard.
BS 5200 Versus JIS BSPP Cone Connections
Some BSPP swivel connections use a 60-degree included cone under British or Japanese standards.
These connections can look extremely similar because they may share:
- BSPP thread sizes
- Parallel threads
- A nominal 60-degree cone
- Similar swivel construction
BS 5200 and JIS B8363 are separate BSPP 60-degree cone systems. Do not assume that a JIS female swivel and a BS 5200 male fitting are interchangeable solely because the threads engage and both appear to have a 60-degree cone.
Cone dimensions, thread lengths and contact locations may differ. In an incorrect combination, the swivel nut may tighten against the fitting body before the sealing surfaces make proper contact.
This distinction is especially important on imported equipment where Japanese and European connections may appear in the same facility.
Worked BSPP Identification Examples
Example 1: Identifying a G 1/2 Male BSPP Port Fitting
An unknown fitting has:
- Straight external threads
- Approximately 20.8-millimeter thread outside diameter
- 14 threads per inch
- A washer beneath the fitting shoulder
- No tapered thread
The chart matches 20.8 millimeters and 14 TPI to G 1/2 BSPP.
The shoulder and washer indicate that the fitting seals against the flat surface surrounding a female port.
Identification: G 1/2 male BSPP port fitting with an external washer-type seal.
Example 2: Identifying a G 3/8 BSPP Swivel
An unknown female swivel has:
- Parallel internal threads
- Approximately 15.2-millimeter internal thread diameter
- 19 threads per inch
- A visible internal conical seat
The measurements match G 3/8 BSPP. The conical seat indicates that the complete connection is a BSPP swivel designed to mate with a compatible male cone.
Identification: G 3/8 female BSPP cone-seat swivel.
The thread measurement alone would not have identified the required seat style.
Example 3: Distinguishing G 1/4 BSPP From 1/4 NPT
A male fitting measures approximately 13 millimeters outside diameter.
Additional inspection shows:
- The thread remains parallel.
- The pitch is 19 threads per inch.
- The thread profile is 55 degrees.
- A bonded washer sits beneath the shoulder.
Those characteristics indicate G 1/4 BSPP.
A 1/4 NPT fitting would normally have a tapered thread, 18 threads per inch and a 60-degree thread profile.
Example 4: Distinguishing BSPP From a Similar Metric Thread
A male fitting measures close to 21 millimeters across the threads.
That measurement could suggest G 1/2 BSPP or a nearby metric size. A pitch gauge shows 14 threads per inch, equal to approximately 1.814 millimeters between threads.
A standard metric thread would normally use a specified metric pitch such as 1.5 or 2.0 millimeters rather than 14 TPI.
The 55-degree profile and external sealing washer further support a G 1/2 BSPP identification.
Common BSPP Identification Mistakes
Assuming BSPP Is Metric
BSPP is common on European equipment, but it is not a metric thread. Equipment origin is only a clue, not proof.
Matching the Nominal Size to the Caliper Reading
A G 1/2 thread does not measure 1/2 inch across the outside. Always use a thread chart.
Measuring Diameter Without Checking Pitch
Several connection systems have similar diameters. Diameter and pitch must be evaluated together.
Checking the Thread but Ignoring the Seal
BSPP identifies the thread. It does not fully identify whether the fitting requires a bonded seal, O-ring, flat washer or conical seat.
Assuming Every BSPP Fitting Uses a Bonded Washer
Bonded seals are common on BSPP ports, but they are not universal. Swivel and cone connections use different sealing arrangements.
Treating BSPP and BSPT as Automatically Interchangeable
Their threads may engage in some combinations, but the connection must be specifically designed for the thread and sealing method being used.
Applying Pipe-Thread Sealant to Create a BSPP Seal
Standard BSPP connections generally do not create a pressure seal on the threads. Thread sealant is not a substitute for the specified washer, O-ring or seat.
Confusing BSPP With NPT
The threads may initially engage, but BSPP and NPT have different thread angles, pitches and taper characteristics.
Assuming All 60-Degree BSPP Cones Are Compatible
BS 5200 and JIS cone connections can appear similar. Verify the complete standard and mating geometry.
Measuring Only One End of an Adapter
A BSPP adapter may transition to JIC, NPT, ORB, metric or another thread system. Each end must be identified independently.
Reusing a Damaged Seal
The metal fitting may be reusable while the bonded washer, O-ring or soft seal requires replacement.
Why Do BSPP Fittings Leak?
BSPP connections commonly leak because the sealing component is missing, damaged, incompatible or compressed against an unsuitable surface.
| Symptom or Problem | Likely Cause | How to Confirm | Corrective Action |
|---|---|---|---|
| Leak beneath fitting shoulder | Missing or damaged bonded seal | Inspect washer and port face | Install the correct new seal |
| O-ring extrusion | Wrong O-ring or excessive gap | Check seal size and retaining ring | Install the specified seal assembly |
| Leak from cone connection | Damaged or mismatched seats | Inspect both cone surfaces | Replace the incompatible or damaged part |
| Threads bind during assembly | Wrong thread type or pitch | Measure diameter and TPI | Stop and identify both components |
| Fitting leaks after reuse | Compressed or hardened seal | Inspect seal condition | Replace the sealing element |
| Washer leaks on cast surface | Port face is uneven | Inspect the spot face | Repair the port or use the correct fitting |
| Leak continues after tightening | Seat or seal is damaged | Depressurize and disassemble | Replace the damaged component |
| Fitting sits at the wrong angle | Non-positionable fitting used | Check adapter configuration | Use an adjustable elbow or tee |
| Connection loosens during use | Hose strain or vibration | Inspect routing and support | Correct alignment and secure the hose |
| Corrosion at sealing face | Material unsuitable for environment | Inspect material and exposure | Select a compatible fitting material |
Why More Tightening May Not Stop a BSPP Leak
Additional torque cannot correct:
- A missing seal
- A cut O-ring
- A damaged bonded washer
- An uneven port face
- A mismatched cone
- Incorrect thread pitch
- Cross-threading
- Side loading
Over-tightening can deform the seal, damage the threads, distort the fitting or crack the port.
Use the installation torque and procedure specified for the exact fitting material, size, manufacturer and sealing design.
How to Select the Correct Replacement BSPP Fitting
Confirm the following before purchasing a replacement.
Thread Size
Record:
- Male or female
- Outside or inside diameter
- Threads per inch
- BSPP or G size
Sealing Method
Identify whether the connection uses:
- Bonded seal
- O-ring and retaining ring
- Soft flat washer
- Conical seat
- Another specified seal
Opposite Connection
Determine whether the opposite end is:
- BSPP
- BSPT
- JIC
- NPT
- ORB
- ORFS
- Metric
- JIS
- DIN
- Flange
Fitting Configuration
Confirm whether the fitting is:
- Straight
- 45-degree elbow
- 90-degree elbow
- Tee
- Cross
- Bulkhead
- Reducer
- Swivel
- Fixed
- Adjustable
Material
Common materials include:
- Plated carbon steel
- Stainless steel
- Brass
The material must be appropriate for the fluid, temperature, pressure, corrosion exposure and equipment environment.
Pressure Rating
Verify the working-pressure rating of the exact fitting. Do not assume that every fitting with the same thread size has the same pressure rating.
The complete system is limited by its lowest-rated component.
Installation Space and Orientation
Check:
- Overall fitting length
- Hex size
- Clearance for a wrench
- Hose routing
- Port orientation
- Space required for elbows and swivel nuts
- Whether an adjustable fitting is required
BSPP Fitting Identification Worksheet
Use this worksheet before ordering a fitting or requesting identification assistance.
Connection End 1
| Identification Item | Measurement or Observation |
|---|---|
| Male or female | |
| Parallel or tapered | |
| Thread outside or inside diameter | |
| Threads per inch | |
| Probable BSPP/G size | |
| Thread profile | |
| Sealing method | |
| Seat or cone angle | |
| Material | |
| Visible markings or part number |
Connection End 2
| Identification Item | Measurement or Observation |
|---|---|
| Male or female | |
| Parallel or tapered | |
| Thread outside or inside diameter | |
| Threads per inch | |
| Probable connection size | |
| Connection standard | |
| Sealing method | |
| Seat or cone angle | |
| Material | |
| Visible markings or part number |
Application Information
| Application Detail | Information |
|---|---|
| Equipment manufacturer | |
| Equipment model | |
| Existing part number | |
| Hydraulic fluid | |
| Maximum working pressure | |
| Operating temperature | |
| Fitting shape | |
| Hose or tube size | |
| Required orientation | |
| Clear photographs available | Yes / No |
Photograph:
- Both connection ends
- The fitting from the side
- Any markings or part numbers
- The original installation
- The caliper measurement
- The pitch gauge positioned on the threads
Frequently Asked Questions About BSPP Fittings
What Does BSPP Stand For?
BSPP stands for British Standard Pipe Parallel. BSPP uses a cylindrical thread that maintains essentially the same diameter along its threaded length.
Is G Thread the Same as BSPP?
G thread is the common designation for the parallel pipe thread generally referred to as BSPP. The designation identifies the thread but does not necessarily identify the fitting’s complete sealing arrangement.
Is BSPP Metric?
No. BSPP is an inch-based thread system using nominal pipe sizes and threads per inch. It is frequently found on European equipment but is not a metric thread.
What Angle Are BSPP Threads?
BSPP threads have a 55-degree included thread angle with rounded crests and roots.
How Do You Measure a Male BSPP Fitting?
Measure the outside diameter across the male thread crests with a caliper. Then determine the threads per inch with a pitch gauge and compare both measurements with a BSPP thread chart.
How Do You Determine Whether a Thread Is BSPP or BSPT?
Measure the thread diameter at two locations. BSPP remains essentially constant because it is parallel. A male BSPT thread becomes smaller toward the end because it is tapered.
What Size Is G 1/2 BSPP?
G 1/2 BSPP has 14 threads per inch and an approximate male thread outside diameter of 0.82 inch, or 20.8 millimeters.
What Size Is G 1/4 BSPP?
G 1/4 BSPP has 19 threads per inch and an approximate male thread outside diameter of 0.51 inch, or 13 millimeters.
Do BSPP Threads Require PTFE Tape or Thread Sealant?
A standard BSPP connection normally seals outside the threads with a washer, O-ring or matching seat. PTFE tape or pipe-thread sealant should not be used as a substitute for the designed sealing method.
Does Every BSPP Fitting Use a Bonded Seal?
No. BSPP fittings may use bonded seals, O-rings, soft washers or matching conical seats, depending on the connection design.
Can BSPP and BSPT Be Connected?
Some tapered BSPT male threads can be used with compatible fixed female parallel threads in specifically designed connections. Do not assume that an arbitrary BSPP and BSPT fitting combination is compatible. Confirm the connection standard and sealing method.
Can BSPP Connect to NPT?
BSPP and NPT should not be treated as interchangeable. They use different thread angles, pitches and profiles, and BSPP is parallel while NPT is tapered.
What Is the Difference Between BSPP and Metric Threads?
BSPP uses a 55-degree thread profile and inch-based threads per inch. Metric threads generally use a 60-degree profile and a pitch specified in millimeters.
Are BS 5200 and JIS BSPP Cone Fittings Interchangeable?
Do not assume they are interchangeable. Both can use BSPP threads and similar-looking cone seats, but they are separate connection systems with potentially different mating dimensions.
Can BSPP Fittings Be Reused?
The metal fitting may be reused when the threads, body and sealing surfaces remain undamaged and the fitting still meets the application requirements.
Inspect and replace O-rings, bonded washers and soft sealing elements when required. Do not reuse a fitting with damaged threads, distorted shoulders, cracked swivel nuts, corroded seats or an uncertain pressure rating.
Need Help Identifying a BSPP Fitting?
A correct replacement requires more than confirming that the thread is parallel.
Before contacting Union Hydraulics, gather:
- Clear photographs of both fitting ends
- Male thread outside diameter or female thread inside diameter
- Threads per inch
- Sealing method
- Seat or cone angle
- Fitting material
- Fitting configuration
- Existing part numbers
- Equipment manufacturer and model
- Maximum system pressure
- Completed BSPP identification worksheet
Union Hydraulics can use this information to help compare the existing connection with available BSPP fitting sizes, sealing methods and adapter configurations.
Once the thread size and sealing style have been confirmed, browse BSPP fittings and adapters or contact Union Hydraulics for assistance selecting the correct replacement.
