{"id":4869,"date":"2026-09-16T08:37:11","date_gmt":"2026-09-16T08:37:11","guid":{"rendered":"https:\/\/www.henghuahose.com\/?post_type=product&p=4869"},"modified":"2026-09-17T00:41:06","modified_gmt":"2026-09-17T00:41:06","slug":"straight-tube-adapters-with-swivel-nut-adapter-3c-3d","status":"publish","type":"product","link":"https:\/\/www.henghuahose.com\/fr\/product\/straight-tube-adapters-with-swivel-nut-adapter-3c-3d\/","title":{"rendered":"Straight Tube Adapter with Swivel Nut 3C \/ 3D (Metric Male 24\u00b0 Cone to Metric Tube Union)"},"content":{"rendered":"
\"Straight<\/figure>\r\n

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Why This Straight Tube Adapter with Swivel Nut 3C \/ 3D Prevents Twisted Tube<\/h2>\r\n\r\n\r\n\r\n

The straight tube adapter with swivel nut 3C \/ 3D<\/strong> is a straight fitting that puts a free-spinning union nut on the tube side and a metric male 24\u00b0 cone stud end on the port side. The nut is captured on the adapter body but rotates independently of it. That single design detail changes what happens during assembly: the body can be held steady with one wrench while the nut is torqued, so no twisting load is transferred into the tube, the tube nut or the hose that is already connected behind it.<\/p>\r\n\r\n\r\n\r\n

On a normal straight adapter both joints fight each other. Tightening the second joint rotates the whole fitting, and that rotation either loosens the joint you just made or winds the line up under stress. The straight tube adapter with swivel nut 3C \/ 3D removes the conflict. The port end is made up first, the tube end second, and the second operation does not disturb the first.<\/p>\r\n\r\n\r\n\r\n

Two series are covered by this drawing: 3C is the light L series<\/strong> and 3D is the heavy S series<\/strong>. Both carry the same architecture \u2014 male 24\u00b0 cone stud end at Connection 1, female 24\u00b0 cone seat with a captive swivel nut at Connection 2 \u2014 and they differ in the wall thickness and thread proportions of the components they mate with, which is what decides the choice between them on a given circuit.<\/p>\r\n\r\n\r\n\r\n

Core Advantages<\/h3>\r\n\r\n\r\n\r\n
    \r\n
  1. Swivel nut decouples the two joints<\/strong> \u2014 the union nut turns freely on the body, so the tube end is made up without rotating the fitting or the line behind it.<\/li>\r\n
  2. No torsional load on the tube<\/strong> \u2014 metal tube assemblies and hoses are not designed to be wound up during final tightening, and this adapter never asks them to be.<\/li>\r\n
  3. Metric 24\u00b0 cone sealing at both connections<\/strong> \u2014 Connection 1 is a male 24\u00b0 cone stud end and Connection 2 is a 24\u00b0 cone seat, so the part stays inside the DIN 3861 \/ ISO 8434-1 tube system rather than mixing sealing principles.<\/li>\r\n
  4. Wrench access from one flat is enough<\/strong> \u2014 because the nut spins, the fitter needs a holding flat on the body and a wrench on the nut, not two opposing wrenches fighting for space.<\/li>\r\n
  5. Light L series and heavy S series from one drawing family<\/strong> \u2014 3C covers standard circuits and 3D covers heavier circuits, which keeps a mixed-standard machine on one spare-parts list.<\/li>\r\n
  6. Traceable and cross-referenced free of charge<\/strong> \u2014 send an old part number, a photograph or a drawing and we will confirm the series, the threads and the lead time within 24 hours.<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n

    Technical Specifications<\/h2>\r\n\r\n\r\n\r\n

    What Is a Swivel Nut Tube Adapter?<\/h3>\r\n\r\n\r\n\r\n

    A swivel nut tube adapter is a straight fitting whose tube-side union nut is not fixed to the body. The nut is retained on the body by a machined shoulder, so it can be drawn back along the body, aligned by hand with the mating thread and turned without transmitting rotation to anything else. Inside the nut is a 24\u00b0 cone seat; when the nut is torqued, the mating male 24\u00b0 cone is pressed into that seat and the two steel faces seal metal-to-metal.<\/p>\r\n\r\n\r\n\r\n

    The port side of the straight tube adapter with swivel nut 3C \/ 3D is a fixed male 24\u00b0 cone stud end. It screws into a port that carries a metric female 24\u00b0 cone seat and seals on the cone in exactly the same way. Both connections therefore rely on the same sealing principle while one of them keeps a free-turning nut, which is what makes the part useful in tight assemblies.<\/p>\r\n\r\n\r\n\r\n

    Series matters here. The 3C light series and the 3D heavy series share the design but not the metal around the thread. Light series parts are matched to light series tube and light series ports; heavy series parts are matched to the heavier tube and port preparation. Mixing a light series adapter with a heavy series port gives a joint that looks assembled and is not.<\/p>\r\n\r\n\r\n\r\n

    Connection 1 \u2014 Metric Male 24\u00b0 Cone Stud End<\/h3>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
    Article<\/th>\r\nDetail<\/th>\r\n<\/tr>\r\n<\/thead>\r\n
    Interface type<\/td>\r\nMetric male stud end with 24\u00b0 cone<\/td>\r\n<\/tr>\r\n
    Sealing method<\/td>\r\nMetal-to-metal 24\u00b0 cone contact in the mating female seat<\/td>\r\n<\/tr>\r\n
    Thread form<\/td>\r\nMetric fine pitch, size-specific (for example M12X1.5, M16X1.5, M22X1.5)<\/td>\r\n<\/tr>\r\n
    Reference form<\/td>\r\nMetric 24\u00b0 cone (DIN 3861 \/ ISO 8434-1 family)<\/td>\r\n<\/tr>\r\n
    S\u00e9rie<\/td>\r\nLight L (3C) and heavy S (3D)<\/td>\r\n<\/tr>\r\n
    Orientation<\/td>\r\nStraight<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n\r\n\r\n\r\n

    Connection 2 \u2014 Metric Tube Union with Swivel Nut<\/h3>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
    Article<\/th>\r\nDetail<\/th>\r\n<\/tr>\r\n<\/thead>\r\n
    Interface type<\/td>\r\nMetric female 24\u00b0 cone seat inside a captive union nut<\/td>\r\n<\/tr>\r\n
    Sealing method<\/td>\r\nMetal-to-metal 24\u00b0 cone contact with the mating male cone stud<\/td>\r\n<\/tr>\r\n
    Nut behaviour<\/td>\r\nFreely rotating, mechanically retained on the body, retained after break-out<\/td>\r\n<\/tr>\r\n
    Thread form<\/td>\r\nMetric fine pitch, matched to the corresponding male cone stud<\/td>\r\n<\/tr>\r\n
    Reference form<\/td>\r\nMetric 24\u00b0 cone (DIN 3861 \/ ISO 8434-1 family)<\/td>\r\n<\/tr>\r\n
    S\u00e9rie<\/td>\r\nLight L and heavy S<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n\r\n\r\n\r\n

    Because the nut is captured rather than loose, it cannot be lost during service and it does not have to be threaded onto the tube before the tube is bent or routed.<\/p>\r\n\r\n\r\n\r\n

    Dimensional Data<\/h3>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
    Symbol<\/th>\r\nSignification<\/th>\r\nUnit<\/th>\r\n<\/tr>\r\n<\/thead>\r\n
    PART NO.<\/td>\r\nCatalogue order code for the size<\/td>\r\n–<\/td>\r\n<\/tr>\r\n
    E<\/td>\r\nMetric male thread at the 24\u00b0 cone stud end<\/td>\r\nmm pitch notation<\/td>\r\n<\/tr>\r\n
    D1, D2<\/td>\r\nTube outside diameter; the drawing labels the two tube ends D1 and D2 and the chart prints one common value per size<\/td>\r\nmm<\/td>\r\n<\/tr>\r\n
    L1<\/td>\r\nOverall length across the adapter body<\/td>\r\nmm<\/td>\r\n<\/tr>\r\n
    L2<\/td>\r\nSecond overall length shown on the drawing<\/td>\r\nmm<\/td>\r\n<\/tr>\r\n
    S1, S2<\/td>\r\nHex across flats on the body and on the swivel nut<\/td>\r\nmm<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n\r\n\r\n\r\n

    Full Part Number Matrix<\/h3>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
    PART NO.<\/th>\r\nE THREAD<\/th>\r\nTUBE O.D. D1, D2<\/th>\r\nL1<\/th>\r\nL2<\/th>\r\nS1, S2<\/th>\r\nPressure Group<\/th>\r\n<\/tr>\r\n<\/thead>\r\n
    3C-12<\/td>\r\nM12X1.5<\/td>\r\n6<\/td>\r\n33<\/td>\r\n32<\/td>\r\n14<\/td>\r\n31.5 MPa, light series L<\/td>\r\n<\/tr>\r\n
    3C-14<\/td>\r\nM14X1.5<\/td>\r\n8<\/td>\r\n33<\/td>\r\n32<\/td>\r\n17<\/td>\r\n31.5 MPa, light series L<\/td>\r\n<\/tr>\r\n
    3C-16<\/td>\r\nM16X1.5<\/td>\r\n10<\/td>\r\n34<\/td>\r\n33<\/td>\r\n19<\/td>\r\n31.5 MPa, light series L<\/td>\r\n<\/tr>\r\n
    3C-18<\/td>\r\nM18X1.5<\/td>\r\n12<\/td>\r\n34<\/td>\r\n33<\/td>\r\n22<\/td>\r\n31.5 MPa, light series L<\/td>\r\n<\/tr>\r\n
    3C-22<\/td>\r\nM22X1.5<\/td>\r\n15<\/td>\r\n39<\/td>\r\n38<\/td>\r\n27<\/td>\r\n31.5 MPa, light series L<\/td>\r\n<\/tr>\r\n
    3C-26<\/td>\r\nM26X1.5<\/td>\r\n18<\/td>\r\n41<\/td>\r\n39<\/td>\r\n32<\/td>\r\n31.5 MPa, light series L<\/td>\r\n<\/tr>\r\n
    3C-30<\/td>\r\nM30X2<\/td>\r\n22<\/td>\r\n44<\/td>\r\n42<\/td>\r\n36<\/td>\r\n16 MPa, light series L<\/td>\r\n<\/tr>\r\n
    3C-36<\/td>\r\nM36X2<\/td>\r\n28<\/td>\r\n48<\/td>\r\n46<\/td>\r\n46<\/td>\r\n16 MPa, light series L<\/td>\r\n<\/tr>\r\n
    3C-45<\/td>\r\nM45X2<\/td>\r\n35<\/td>\r\n52<\/td>\r\n48<\/td>\r\n50<\/td>\r\n16 MPa, light series L<\/td>\r\n<\/tr>\r\n
    3C-52<\/td>\r\nM52X2<\/td>\r\n42<\/td>\r\n57<\/td>\r\n52<\/td>\r\n60<\/td>\r\n16 MPa, light series L<\/td>\r\n<\/tr>\r\n
    3D-14<\/td>\r\nM14X1.5<\/td>\r\n6<\/td>\r\n33<\/td>\r\n32<\/td>\r\n17<\/td>\r\n63 MPa, heavy series S<\/td>\r\n<\/tr>\r\n
    3D-16<\/td>\r\nM16X1.5<\/td>\r\n8<\/td>\r\n34<\/td>\r\n33<\/td>\r\n19<\/td>\r\n63 MPa, heavy series S<\/td>\r\n<\/tr>\r\n
    3D-18<\/td>\r\nM18X1.5<\/td>\r\n10<\/td>\r\n35<\/td>\r\n33<\/td>\r\n22<\/td>\r\n63 MPa, heavy series S<\/td>\r\n<\/tr>\r\n
    3D-20<\/td>\r\nM20X1.5<\/td>\r\n12<\/td>\r\n38<\/td>\r\n36<\/td>\r\n24<\/td>\r\n63 MPa, heavy series S<\/td>\r\n<\/tr>\r\n
    3D-22<\/td>\r\nM22X1.5<\/td>\r\n14<\/td>\r\n41<\/td>\r\n39<\/td>\r\n27<\/td>\r\n63 MPa, heavy series S<\/td>\r\n<\/tr>\r\n
    3D-24<\/td>\r\nM24X1.5<\/td>\r\n16<\/td>\r\n42<\/td>\r\n39<\/td>\r\n30<\/td>\r\n40 MPa, heavy series S<\/td>\r\n<\/tr>\r\n
    3D-30<\/td>\r\nM30X2<\/td>\r\n20<\/td>\r\n48<\/td>\r\n44<\/td>\r\n36<\/td>\r\n40 MPa, heavy series S<\/td>\r\n<\/tr>\r\n
    3D-36<\/td>\r\nM36X2<\/td>\r\n25<\/td>\r\n53<\/td>\r\n46<\/td>\r\n46<\/td>\r\n40 MPa, heavy series S<\/td>\r\n<\/tr>\r\n
    3D-42<\/td>\r\nM42X2<\/td>\r\n30<\/td>\r\n62<\/td>\r\n52<\/td>\r\n50<\/td>\r\n40 MPa, heavy series S<\/td>\r\n<\/tr>\r\n
    3D-52<\/td>\r\nM52X2<\/td>\r\n38<\/td>\r\n67<\/td>\r\n52<\/td>\r\n60<\/td>\r\n31.5 MPa, heavy series S<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n\r\n\r\n\r\n
    \r\n

    The table above is transcribed in full from the 3C \/ 3D specification drawing: 10 light series L rows and 10 heavy series S rows, each carrying the metric stud thread E, the tube outside diameter printed for that size (the drawing dimensions both tube ends as D1 and D2, and the chart gives one value for the pair), the dimensions L1 and L2, the hexes S1 and S2, and the pressure grade printed against that row. The 31.5 MPa light series block ends at 3C-26 and the 16 MPa light series block starts at 3C-30; the 63 MPa heavy series block ends at 3D-22 and the 40 MPa block starts at 3D-24. Order by the full PART NO. as printed rather than by thread size alone, because the same thread size appears in both the light series L list and the heavy series S list.<\/p>\r\n<\/blockquote>\r\n\r\n\r\n\r\n

    Materials and Finish<\/h3>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
    Component<\/th>\r\nStandard material<\/th>\r\n<\/tr>\r\n<\/thead>\r\n
    Body (3C \/ 3D)<\/td>\r\nCarbon steel, machined from bar or forged stock<\/td>\r\n<\/tr>\r\n
    Swivel nut<\/td>\r\nCarbon steel, machined, mechanically retained on the body<\/td>\r\n<\/tr>\r\n
    Surface protection<\/td>\r\nPlated finish as standard practice for hydraulic adapters<\/td>\r\n<\/tr>\r\n
    Sealing element<\/td>\r\nNone at either cone \u2014 both joints are metal-to-metal<\/td>\r\n<\/tr>\r\n
    Alternative on request<\/td>\r\nStainless steel body and nut<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n\r\n\r\n\r\n

    Working Pressure and Operating Envelope<\/h3>\r\n\r\n\r\n\r\n

    A straight tube adapter with swivel nut 3C \/ 3D carries two cone joints, and the working pressure of the assembly is set by the weaker of the two connections and by the tube that is attached to it. Pressure therefore depends on the thread size, the tube outside diameter and wall thickness, the material of the mating stud, the class of the port and the operating temperature. The light L series covers the moderate-pressure circuits for which light series tube is specified, and the heavy S series covers the circuits for which heavy series tube and heavier ports are specified.<\/p>\r\n\r\n\r\n\r\n

    Because the swivel nut joint is a cone joint rather than a face seal, temperature capability is high and there is no elastomer to age out. Request the size-specific pressure table with your enquiry and we will return the rating for the exact thread pair and tube size you are running.<\/p>\r\n\r\n\r\n\r\n

    How the Swivel Nut Changes Assembly Practice<\/h2>\r\n\r\n\r\n\r\n

    Traditional practice with a fixed straight adapter is to make up the port joint first, then hold the body with a wrench while the tube nut is tightened \u2014 and to accept that some rotation will still be transferred. On thin-wall tube or on a hose that has already been routed around an obstacle, that rotation is the beginning of a fatigue crack or a loosened joint \u2014 which is precisely the failure mode the straight tube adapter with swivel nut 3C \/ 3D is designed to prevent.<\/p>\r\n\r\n\r\n\r\n

    With a swivel nut the sequence becomes cleaner in four ways:<\/p>\r\n\r\n\r\n\r\n

      \r\n
    1. The body can be oriented before the tube joint is made.<\/strong> The fitter sets the body flat, then brings the tube up to it, rather than bending the tube to meet a fixed fitting.<\/li>\r\n
    2. Holding torque is separated from tightening torque.<\/strong> One wrench holds the body flat, the second wrench turns the nut. Nothing rotates that should not rotate.<\/li>\r\n
    3. The nut can be re-tightened without disturbing anything else.<\/strong> If a joint needs a check after a pressure test, the nut turns against the body shoulder and the port joint stays as it was.<\/li>\r\n
    4. The nut stays on the fitting.<\/strong> It is captured, so a service operation cannot leave a union nut rolling around inside a machine frame.<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n

      For maintenance teams this last point alone tends to justify the swivel design, because the most common field complaint about conventional adapters is not the seal \u2014 it is the inaccessible wrench position created by a fitting that will not stay still.<\/p>\r\n\r\n\r\n\r\n

      Installation Notes for the Straight Tube Adapter with Swivel Nut 3C \/ 3D<\/h2>\r\n\r\n\r\n\r\n
        \r\n
      1. Check both cones first.<\/strong> Inspect the male 24\u00b0 cone and the seat inside the swivel nut for dents, burrs or dirt. A metal-to-metal cone will not seal across a scratch.<\/li>\r\n
      2. Make up the port joint first.<\/strong> Thread the male stud end into the metric female 24\u00b0 cone port by hand, then torque to the value specified for that thread size and port material.<\/li>\r\n
      3. Draw the swivel nut back<\/strong> along the body until the mating tube cone is clear, align the tube, and start the nut by hand. Never start a cone joint with a wrench.<\/li>\r\n
      4. Hold the body flat and turn only the nut.<\/strong> Use the body hex for the holding wrench and the nut hex for the tightening wrench.<\/li>\r\n
      5. Torque to the value for the tube size and series,<\/strong> then check that both connections remain static while the second torque is applied.<\/li>\r\n
      6. Pressure-test the complete assembly.<\/strong> Two cone joints are independent; test both before the machine goes back into service.<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n

        Applications<\/h2>\r\n\r\n\r\n\r\n

        The straight tube adapter with swivel nut 3C \/ 3D is specified wherever a straight transition is needed and the tube or hose behind it must not be rotated during assembly. Typical installations include:<\/p>\r\n\r\n\r\n\r\n