Cone and Thread vs Compression Fittings: How to Choose the Right Tube Connection
Cone-and-thread and compression fittings solve the same problem in different ways: sealing a tube to a component. A cone-and-thread (coned-and-threaded) fitting machines the tube end into a cone with external threads, then seats it metal-to-metal. That's suited to medium- and high-pressure service. A compression (ferrule) tube fitting takes a different route: it swages one or two ferrules onto a plain-cut tube, which makes for fast, gaugeable instrumentation assembly.
On this page, "compression fitting" refers specifically to an instrumentation-grade stainless or high-alloy ferrule tube fitting, not the copper or plumbing kind. And "cone and thread" means a machined, high-pressure tubing connection, not a threaded pipe joint.
Crestflo makes both systems, so this comparison isn't slanted; it's tied straight to spec. Compression tube fittings undergo testing per ASTM F1387. High-pressure cone-and-thread fittings, by contrast, are rated to 30,000 psi, and the catalog's top-end tiers reach as high as 60,000 psi. The Crestflo Engineering Team reviewed this comparison.
TL;DR: The Difference Between Cone and Thread and Compression Fittings
When it comes to sealing a tube to a component, cone-and-thread and compression are the two main tube fitting types. Go with cone-and-thread once working pressure pushes into the medium- and high-pressure range (think waterjet/UHP, HPHT oil and gas, hydrogen, reactor and test-rig service) and you're willing to machine each heavy-wall tube end. Compression makes more sense for general instrumentation. Impulse and sensing lines, analyzer and sample systems, gas panels, MRO work, that sort of thing, where a clean square cut, hand tools and a make-up gauge get you a repeatable seal with no machining required. The compression joint wins on speed and field convenience. Cone-and-thread wins on pressure, by a wide margin.
Cone and Thread and Compression Fittings: Names and Designations
Engineers use a lot of different names for these two connection systems. A cone-and-thread fitting also goes by coned-and-threaded fitting, cone & thread (C&T) fitting, gland-and-collar or gland-and-sleeve connection, medium-pressure (MP) fitting, high-pressure (HP) fitting, anti-vibration collar fitting, and autoclave-style fitting; the tube itself gets called a coned tubing connection. A compression fitting shows up under just as many labels: ferrule fitting, nut-and-ferrule fitting, twin-ferrule, double-ferrule, or two-ferrule fitting, single-ferrule fitting, bite-type ferrule fitting, or simply instrumentation tube fitting. When people search for guidance, they tend to phrase it as compression vs cone and thread, difference between cone and thread and compression, or is cone and thread stronger than compression. All three questions point to the same underlying decision.
What Is a Compression (Ferrule) Tube Fitting?
Tighten the nut on a compression tube fitting, and it drives one or two ferrules radially onto the tube's outside diameter. That's how the seal happens. The ferrule bites into the tube and grips it, forming a metal-to-metal seal against both the tube surface and the fitting body. No machining on the tube end, no elastomer needed for the primary seal. Twin-ferrule, or double-ferrule, designs split sealing and gripping duties between a front and back ferrule. That split helps the joint stand up to vibration and thermal cycling. Single-ferrule designs are simpler, and they're widely used on lower-duty instrumentation lines.
Crestflo compression tube fittings meet ASTM F1387, and come in single- and double-ferrule versions, with hardened or non-hardened ferrules built to spec. Sizes run imperial and metric, with end connections reaching 2 inch (50 mm) OD. Assembly discipline is what makes or breaks the joint: the tube's OD and wall thickness have to be right, and the make-up needs proper gauging. Skip either step and you've got a leak path, not a seal. That's exactly why F1387 performance qualification and gaugeable make-up aren't optional extras. Take a look at the full range of stainless steel compression tube fittings, single-ferrule tube fittings and nut-and-ferrule sets, or read single vs double ferrule explained.
What Is a Cone-and-Thread (Coned & Threaded) Fitting?
A cone-and-thread fitting seals by machining the tube end into a matching cone, then cutting an external thread just behind it. A threaded collar, or sleeve, works together with a gland nut to draw the coned tube into a female cone inside the fitting body, preloading a metal-to-metal seat. The collar also grips the line to resist vibration on high-pressure runs. Because the seal relies on a machined metal seat rather than a swaged ferrule, this design handles far higher working pressure and holds up in elevated-temperature service, limited only by the tube alloy itself.
Cone-and-thread connections split into two classes: medium-pressure (MP) and high-pressure (HP). Crestflo's high-pressure cone-and-thread fittings come in high-tensile stainless steel, rated to 30,000 psi. The catalog's high-pressure tiers stretch further still, up to 60,000 psi, and alloy versions ship on request, PED-compliant where needed. These are high-pressure tube fittings, and that's the whole point: they hold working pressure a ferrule joint just can't. Check out the high-pressure cone-and-thread fittings, or browse the broader line of high-pressure instrumentation fittings (to 60,000 psi).
Cone and Thread vs Compression: At a Glance: Which Connection Do You Need?
| Choose this if… | Cone & Thread | Compression (Ferrule) |
|---|---|---|
| Working pressure is the priority | ✔ Medium/high pressure to 30,000 psi (HP tiers to 60,000 psi) | Instrumentation pressures, falling with tube OD/wall |
| You want no tube machining | Requires coning + threading each tube end | ✔ Clean square cut + deburr only |
| Install speed / field make-up matters | Slower; shop or skilled field work | ✔ Fast, gaugeable hand-tool make-up |
| You need frequent remakes | Re-makeable; re-cone if the end is damaged | ✔ Ferrule stays swaged; re-make readily |
| You need broad exotic-alloy choice | High-tensile SS standard; alloy on request | ✔ Full SS + high-nickel + CRA + titanium range |
| Cost and lead-time sensitivity | Higher install effort per joint | ✔ Lower install effort, standard tube |
Cone and Thread vs Compression: Head-to-Head Attribute Comparison
| Attribute | Cone-and-Thread (Coned & Threaded) | Compression (Ferrule) Tube Fitting |
|---|---|---|
| Working principle | Machined cone on the tube seats metal-to-metal into a female cone; a threaded collar + gland nut preload the joint | One or two ferrules swage onto the tube OD as the nut is torqued; the ferrule grips and seals |
| Seal type | Metal-to-metal coned seat | Metal-to-metal ferrule-to-tube + ferrule-to-body |
| Tube-end preparation | Required, cone and external thread machined with a coning tool + threading die; heavy-wall tube | None, clean square cut + deburr; standard instrument tube |
| Typical pressure class | Medium/high pressure; Crestflo to 30,000 psi, catalog tiers to 60,000 psi | Instrumentation service to 2 inch (50 mm) OD; rating falls with tube size and wall (per applicable tube-rating tables; customizable to requirement) |
| Temperature | Governed by tube alloy and any packing; the metal seat suits elevated temperature, confirm the rating for your service on request | Metal seal; temperature governed by the alloy |
| Size range | Medium/high-pressure small-bore tube per applicable high-pressure tube schedules, specify OD/wall on the RFQ | 1/8″–2″ OD imperial and 6–50 mm metric; both offered on all fittings |
| Material options | High-tensile stainless steel standard; alloy on request | 304/304L, 316/316L, 904L, duplex/super-duplex, 254 SMO, AL-6XN, Alloy 20, Inconel/Incoloy/Monel/Hastelloy, Nickel 200/201, Titanium Gr2 |
| Ferrule options | None (no ferrule) | Single and double ferrule; hardened and non-hardened to requirement |
| Installation effort | Higher, machining + make-up; shop or skilled field | Lower, hand tools + gauge; field-friendly make-up |
| Reusability / remake | Re-makeable; re-cone if the tube end is damaged | Re-makeable; ferrule stays swaged on the tube after first pull-up |
| Vibration / fatigue | Collar gives anti-vibration grip on HP lines | Twin-ferrule design resists vibration and thermal cycling |
| Standards / interchange basis | Proprietary MP/HP geometries by manufacturer, verify the mating cone, thread and collar before mixing | ASTM F1387 performance qualification (the interchange anchor) |
| Best-fit service | Waterjet/UHP, HPHT oil & gas, hydrogen, chemical injection, reactor/autoclave, hydraulic test rigs | Impulse/sensing lines, analyzer & sample systems, gas panels, MRO |
High Pressure Fitting Types: Instrumentation, Medium and High-Pressure Classes
Pressure class narrows things down fastest. Compression tube fittings dominate instrumentation-duty lines; push the ratings higher, and the coned-and-threaded design takes over. The table below maps each class to the Crestflo family that owns it.
| Class | Typical role | Crestflo product |
|---|---|---|
| Instrumentation (compression) | Sensing, sampling, gas panels, MRO | Compression tube fittings |
| Medium / high pressure (cone-and-thread) | HPHT, waterjet, hydrogen, reactor lines to 30,000 psi | Cone-and-thread fittings |
| 20,000 psi tier | Ultra-high-pressure test and injection | 20,000 psi rated fittings |
| 60,000 psi tier | UHP / waterjet extremes | 60,000 psi rated fittings |
Working-pressure values track the applicable tube schedules and standard rating tables, and they're customizable to specific requirements. For the sizing math behind these figures, see tube sizing & wall thickness and pressure, temperature derating.
Tube Preparation and Wall Thickness for Cone and Thread vs Compression
Tube preparation marks the clearest practical divide between the two systems. Preparing cone and thread tubing calls for heavy-wall tube and dedicated tooling: a coning tool to machine the seat angle and a threading die to cut the external thread. Every joint becomes a small machining operation. Compression needs only a clean, square, deburred cut on standard instrument tube, the ferrules handle the rest at make-up.
Correct tube OD and wall selection matters for both. Too thin a wall won't support a coned seat, and an out-of-tolerance OD compromises ferrule grip. See tube sizing & wall thickness and ferrule installation & gauging.
Installation, Remake and Reusability
Compression fittings go together with hand tools and a make-up gauge, so they're field-friendly and quick to remake. The ferrule stays swaged onto the tube after the first pull-up, which means reconnecting to the same body is straightforward. Cone-and-thread joints take longer to build, since each tube end needs coning and threading before assembly. They can be remade too, but a damaged coned end has to be re-machined before it seals again. If your program depends on frequent field disconnection and remake, compression is the lower-friction choice. If it demands maximum pressure with only occasional make-up, cone-and-thread is worth the extra effort.
Cone and Thread vs Compression Materials: 316, Duplex, Inconel, Monel and Titanium
Compression tube fittings come in the full range of instrumentation alloys, while standard cone-and-thread fittings are made from high-tensile stainless, with alloy versions available on request. The UNS numbers listed below are standard published designations.
| Alloy | UNS | Compression | Cone & Thread | Grade page |
|---|---|---|---|---|
| 316 / 316L | S31600 / S31603 | ✔ | Standard SS | 316/316L stainless |
| 304 / 304L | S30400 / S30403 | ✔ | On request | 304/304L |
| 904L | N08904 | ✔ | On request | 904L |
| Duplex 2205 | S32205 | ✔ | On request | Duplex 2205 |
| Super Duplex 2507 | S32750 | ✔ | On request | Super Duplex 2507 |
| 254 SMO | S31254 | ✔ | On request | 254 SMO |
| AL-6XN | N08367 | ✔ | On request | AL-6XN |
| Alloy 20 | N08020 | ✔ | On request | Alloy 20 |
| Inconel 625 | N06625 | ✔ | On request | Inconel 625 |
| Incoloy 825 | N08825 | ✔ | On request | Incoloy 825 |
| Monel 400 | N04400 | ✔ | On request | Monel 400 |
| Hastelloy C-276 | N10276 | ✔ | On request | Hastelloy C-276 |
| Titanium Gr2 | R50400 | ✔ | On request | Titanium Gr2 |
When you're dealing with chloride or sour service, start with super duplex 2507 for chlorides and sour-service (NACE) selection. Crestflo covers each grade in depth. Supply, though, is limited to instrumentation forms: fittings, valves and tubing, all available through the instrumentation fitting alloys hub.
Standards, Testing and Interchange
Compression tube fittings follow a defined basis for interchange: ASTM F1387 performance qualification for mechanically attached fittings, and that's what Crestflo relies on to back dimensional interchange. Cone-and-thread geometries, though, are proprietary to each manufacturer. No single ASTM interchange spec covers them, so the mating cone, thread and collar need to be checked before you mix brands. Crestflo qualifies compression interchange to F1387 and won't publish a made-up cone-and-thread cross-reference. Ask for your part-number cross-reference instead, and our engineering team will confirm it against your existing fittings.
Both systems share one quality system. They're ISO 9001 / 14001 / 45001 & PED certified, with NACE MR0175 / ISO 15156 conformance where called for. Every part gets marked with its heat/lot number for full traceability, EN 10204 MTC 3.1 as standard and 3.2 on request. Testing runs deep: hydraulic proof, burst and impulse, pneumatic, flexure fatigue, rotary flex, vibration and thermal cycling on the compression range. PMI is performed on delivered material. Crestflo has more detail here: ASTM F1387 performance qualification, why mixing tube fitting brands is risky, and the NPT vs NPTF thread guide.
When to Choose Cone and Thread vs Compression: By Application
For general process, analytical and sensing service, the bulk of plant instrumentation, compression tube fittings give the fastest connection to maintain and the widest choice of alloys. High-pressure and high-temperature duty asks for more than a ferrule can give. Cone-and-thread carries that load instead, which is why it turns up in hydrogen service fittings, high-pressure oil & gas instrumentation, chemical injection, reactor/autoclave rigs and waterjet lines. Many panels run both: compression on the low-pressure sensing side, cone-and-thread on the high-pressure supply. That's one good reason to buy both from a single manufacturer, such as Crestflo, that tests each type properly.
Why Source Both Cone and Thread and Compression Fittings From Crestflo
Crestflo builds both connection systems: ferrule compression fittings qualified to ASTM F1387, and cone-and-thread fittings rated to 30,000 psi, engineered as US drop-in replacements. Standard items ship from ready stock, specials get made to order, and delivery runs 6–8 weeks, against the 20-plus-week lead times typical of the majors. Small MOQ and private label are both available. Every fitting ships in imperial and metric sizes, and heat-number traceability with MTC 3.1/3.2 backs every part. Crestflo is the instrumentation division of a four-decade-old export house recognized by the Government of India, with a proven delivery track record across the Middle East. Origin is Indian, though US or European melt can be arranged on request, backed by full material traceability. See US origin & TAA compliance and our 6–8 week lead time page for details. We Engineer Confidence.
Request a Quote or Cross-Reference
Give us your pressure, tube, media and installation context, and Crestflo's engineers will specify the right connection and alloy. Request a quote or request a sample, and for made-to-print work, talk to an engineer. Reach our US team at sales@crestflousa.com · +1 346 594 9005 · Houston, TX. We'll send datasheets and CAD to customers on request.
Frequently Asked Questions: Cone and Thread vs Compression Fittings
What is the difference between cone-and-thread and compression fittings?
Cone-and-thread machines a coned, threaded end onto the tube, then seals metal-to-metal against a female cone under a threaded collar. It handles medium and high pressure up to 30,000 psi. Compression fittings work differently: they swage one or two ferrules onto a plain-cut tube, giving fast, gaugeable instrumentation make-up without any tube machining.
Which holds higher pressure, cone-and-thread or compression?
Cone-and-thread. Crestflo's cone-and-thread fittings handle pressures to 30,000 psi, and the high-pressure catalog tiers push that ceiling to 60,000 psi. Compression fittings cover instrumentation work instead, rated up to 2 inch (50 mm) OD. That rating isn't fixed, though: it drops as tube size and wall thickness change.
What are the disadvantages of compression fittings?
They depend on getting the tube OD and wall right, along with make-up gauged properly. An under-tightened connection is a potential leak path. At very high pressure, a coned-and-threaded or high-pressure design is the better choice. Crestflo compression fittings are qualified per ASTM F1387 to control that risk, meeting F1387 requirements.
Do compression fittings use NPT?
The ferrule seals against the tube, not a thread. That said, the fitting's pipe-end connection can be NPT, BSP, SAE-ORB, or some other thread type. Check Crestflo's NPT vs NPTF thread guide to pin down and specify the end.
Do plumbers use compression fittings?
Plumbing relies on copper and brass compression fittings for water lines. That's a different product from the stainless and high-alloy instrumentation compression fittings discussed here, built for process, gas and hydraulic sensing lines.
Why are compression fittings restricted on automotive brake lines?
That rule covers automotive brake systems only, and it falls outside what this page addresses. Instrumentation tube fittings aren't governed by it. They're pressure-tested to ASTM F1387 instead, for process and analytical service.
Do I need special tooling for cone-and-thread fittings?
Yes. A coning tool and a threading die machine each shape the heavy-wall tube end before assembly. That makes cone-and-thread more demanding on shop equipment and operator skill than compression make-up, which needs only hand tools and a gauge.
Can I interchange cone-and-thread fittings between brands?
Medium- and high-pressure cone-and-thread geometries are proprietary, so don't mix components without checking the mating cone, thread and collar first. Crestflo qualifies dimensional interchange for compression fittings per ASTM F1387. Request your cross-reference, and our engineering team will confirm the equivalent under F1387.
What alloys can I get for each system?
We build compression fittings in 304, 316, 904L, duplex and super-duplex grades, plus 254 SMO, AL-6XN, Alloy 20, Inconel, Monel, Hastelloy, Nickel 200/201 and Titanium Gr2. Cone-and-thread fittings come in high-tensile stainless, with alloy versions available on request. For the full rundown, check the instrumentation fitting alloys hub.