--- title: "How to Cut Plastic Tubing for Push-In Fittings" canonical: "https://yuannaitube.com/how-to-cut-pneumatic-tubing/" language: "en-US" --- RESOURCES # How to Cut Plastic Tubing for Push-In Fittings By [YUANNAI TUBE]() Published 2026-11-09Updated 2026-11-09 ![Tube cutter beside a square-cut blue polyurethane tube and a black nylon tube]() **To cut plastic tubing for a push-in fitting, depressurize the line, cut the tube at a right angle with a purpose-made tube cutter, check that the end is clean and round, and push it all the way in.** Most leaks at a push-in fitting trace back to a slanted, ragged or short-inserted tube, not to the fitting. This guide covers the steps, the tools to avoid and what to do when a joint leaks. **Quick answer.** Use a tube cutter, not pliers, nippers or scissors; cut square to the tube axis and leave the tube slightly long; push it in until it stops; pull back gently to confirm the grip. A tube that has been in a fitting must have its marked end cut off before it is reused. The same steps apply to PU, PA6, PA12 and **PE tubing**. ## Why a square cut matters A push-in fitting seals on the outside surface of the tube, where an internal O-ring presses around the full circumference. A slanted cut leaves one side of the tube short of the seal, and a crushed or burred end can score the O-ring as the tube goes in. SMC’s fitting precautions state the cutting requirement directly: cut the tubing perpendicularly, being careful not to damage the outside surface, and do not use pliers, nippers or scissors, because the tube will be deformed and trouble may result. ## Tools: what to use and what to avoid | Tool | Result on the tube end | Use for push-in fittings? | | --- | --- | --- | | Tube cutter (single-blade, guided) | Square, clean, round end | Yes | | Sharp utility knife with a guide block | Square if the guide is used, can leave a burr | Acceptable for soft tube, check the end | | Scissors | Squeezed, often slanted end | No | | Side cutters or nippers | Crushed, deformed end | No | | Hacksaw | Rough end with swarf | No | Cutters are made for a stated tube diameter range, so check the rating before you buy one. SMC’s TK series cutters, for example, are listed for nylon, soft nylon, polyurethane and other soft **plastic tubing**, and the catalog entries give different maximum diameters for different models. Hard tubing such as PA12 and PA6 needs a sharp blade and a firm, even cut. For our own sizes, see the [tubing size chart]() and the [PA12 nylon tubing]() and [PU tubing]() pages. ## Steps 1. **Depressurize.** Shut off the supply and exhaust all compressed air from the line before you remove or cut tubing. 2. **Measure with an allowance.** Cut a little longer than the finished length. SMC’s precautions say the same, and they also ask for a sufficient margin for changes in tube length under pressure. 3. **Cut square.** Hold the tube straight in the cutter and cut once, without rocking or sawing. 4. **Inspect the end.** It should be round, flat and free of burrs or splits. If it is not, trim again. 5. **Insert fully.** Push the tube in until it comes to a stop. A tube that is only part way in can leak or release. 6. **Test the grip.** Pull the tube back gently. SMC’s precautions call this checking for a positive seal. ## If a joint leaks - **Re-cut the tube.** Release the fitting, cut off the end that sat in the fitting so that the marked portion is gone, and insert again. SMC notes that when tubing is reused, the previously lodged portion must be removed, or it can cause leakage and make the tube hard to remove. - **Check the outside diameter.** A tube outside the fitting’s tolerance will not seal. SMC advises against using tubing whose outside diameter differs from the stated dimensions. Our PU and **PE tubing** in the shared metric sizes is listed at ±0.10 mm on the outside diameter; see the [fitting match guide]() . - **Check for a sharp bend at the fitting.** The **bend radius** next to a fitting should be at least the tube’s minimum **bend radius** (see [pneumatic tubing bend radius]() ). - **Replace damaged tube.** Cracked, crushed or twisted tubing should be replaced, not repaired. ## Cutting for inspection and samples If you are checking a delivery, cut a short sample from the end of the roll and look at the wall, the ovality and the surface. The [sample testing guide]() and the [receiving inspection checklist]() give the checks in order. ## How to cut plastic tubing FAQ What is the best way to cut plastic tubing? Use a tube cutter that matches the tube diameter, hold the tube straight and make one clean cut at a right angle to its axis. Can I cut air tubing with scissors? It is not recommended for push-in fittings. Scissors squeeze the tube and often leave a slanted end, which can leak at the O-ring. SMC’s precautions say not to cut the tube with pliers, nippers or scissors. Why does my push-in fitting leak after I cut the tube? The usual causes are a slanted or ragged cut, a tube that is not pushed in to the stop, a tube outside the fitting’s diameter tolerance, or a sharp bend at the fitting. Re-cut the tube and insert it fully. How do I cut tubing straight? Use a guided cutter, or a knife against a square guide block, and cut in a single stroke. Check the end by eye before inserting. Can I reuse tubing after taking it out of a fitting? Yes, if the end is cut off first. SMC advises removing the previously lodged portion before reuse, because it can cause leakage. ## Sources and scope - [SMC, fittings and tubing precautions (one-touch fittings: attaching tubing, bending radius, maintenance)]() - [SMC, TK series tube cutters (catalog entries)]() The cutting steps follow the manufacturer precautions above and general workshop practice. Cutter diameter ratings differ by model, so confirm the rating of the tool you use. For fitting-specific instructions, follow your fitting maker’s manual. Content review: [zhangkexin]() · Marketing Review scope: market information and document references. ## Tell us what your application needs. Send your dimensions, operating conditions and quantity. Let’s identify the right tubing for your project. [Request a Quote →]() ## Related tubing products ![Multi-Lumen Tubing]() [Specialty]() ### Multi-Lumen Tubing Custom multi-lumen (multi-bore, multi-core) tubing: twin and multi-line parallel lines for equipment integration. 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