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ASME B107.36-2002 — Pliers: Locking, Clamp, and Tubing Pinch-Off
🔧 ASME B107.36-2002 is a substandard of the ASME B107 family, Hand Tools and Accessories, covering locking pliers, clamp pliers, and tubing pinch-off pliers — the dimensional and functional characteristics of these tools for clamping operations in assembly and repair work. “Locking” means the pliers remain self-locked after the jaws close through an eccentric/toggle mechanism, maintaining clamping force without the operator’s continued grip — the standard basis for the tools commonly known as Vise-Grip type pliers. A principal change in this edition is the allowance of any material that meets the specified performance and safety requirements, moving from designated materials to performance-based acceptance.
💡 The core value of locking pliers is hands-free operation: after clamping, the jaws lock themselves and the operator can use both hands for welding, assembly, or forming — something ordinary pliers cannot do. The Standard defines requirements around exactly that function.
1. Scope and Classification 📌
The Standard covers locking clamp pliers and tubing pinch-off pliers suitable for clamping operations in assembly and repair work, classified as follows:
- Type I — Clamp pliers:
- Class 1 — “C” Clamp: Style A fixed and Style B fixed, with swivel pads.
- Class 2 — Sheet metal clamp: flat, wide jaws for gripping and forming thin sheet.
- Class 3 — Welding clamp: for temporarily holding workpieces during welding, with profiles suited to structural shapes.
- Type II — Tubing pinch-off pliers: used to pinch off the flow of gas or other material through rubber or soft copper tubing; the jaws are radiused to straddle the tube, with depth-limiting stops to avoid damaging the tube wall.
| Type / Class | Construction | Typical Applications |
|---|---|---|
| Type I, Class 1, Style A (C clamp, fixed) | C-shaped jaws, fixed pads, self-locking | General woodworking and metalwork clamping |
| Type I, Class 1, Style B (C clamp, swivel pads) | C-shaped jaws + swivel pads | Gripping cylinders without scratching the work |
| Type I, Class 2 (sheet metal) | Flat, wide jaws | Thin sheet gripping, sheet metal forming |
| Type I, Class 3 (welding) | Profile-adapted jaws | Welding positioning, temporary fixture |
| Type II (tubing pinch-off) | Radiused jaws + depth limit | Pinching off flow in rubber/soft copper tubing |
2. Design Requirements: Locking and Release Mechanisms 🔩
Section 4 requires the pliers to be provided with a toggle or cam device with an adjustable mechanism so the jaws can be clamped and locked. The pliers must be released by hand, anywhere within the pliers’ capacity, by either of the typical trigger release mechanisms shown in Fig. 1. Specific requirements include:
- Locking capability: after closure the jaws lock themselves and resist opening under reverse force.
- Adjustable mechanism: a rear screw adjusts jaw opening and clamping force for different workpiece thicknesses.
- Release: a one-hand trigger releases the jaws quickly at any clamped position within the pliers’ capacity.
- Materials: materials must produce pliers meeting the requirements (any conforming material is allowed in this edition); test specimens must withstand the applicable tests without cracking or breaking.
⚠️ The illustrations in the Standard are descriptive, not restrictive: as long as the product meets the requirements, manufacturers may use designs different from the figures. Acceptance checks functional characteristics — locking, adjustability, and release — not whether the appearance matches the figures exactly.
3. Test Methods: Locking Load Test 🔬
Section 5 defines the test procedures, centered on the locking load test:
- Type I clamp pliers are clamped in the specified position on a test fixture and loaded to the prescribed value; the jaws must remain locked, with no slippage, permanent deformation, or fracture.
- The release mechanism is verified at various clamping positions to ensure smooth release.
- Tests follow ASME B107.25M (Pliers — Performance Test Methods) and related documents; specimens must survive the prescribed tests undamaged.
💡 In production and acceptance, focus on: reliable locking on thin workpieces, no slippage on thick workpieces, and smooth trigger release at all jaw openings — exactly the aspects most likely to fail in hands-free use.
4. Engineering Practice and Use Notes 🛠️
- 🔍 Selection: choose by the job — Type I for clamping sheet and shapes, Type II for pinching off gas/medium flow; prefer Style B swivel-pad versions for cylindrical surfaces.
- 🔧 Adjusting clamping force: open the adjusting screw, slip the jaws over the workpiece, then tighten the screw to the desired opening; close the handles to lock. Do not force additional pressure once locked.
- 📊 Pinch-off use: position the jaws perpendicular to the tube axis and press slowly to the limit stop, which limits jaw closure and prevents cutting through the tube wall.
- 📋 Regular inspection: check jaw wear, adjusting-thread condition, and trigger smoothness; stop using any pliers with cracks or distortion.
🚨 Locking pliers’ gripping force rises sharply with adjustment depth — adjust carefully when clamping fragile or thin-walled workpieces. Before pinching a pressurized soft tube, ensure the medium is depressurized to avoid spraying or injury.
5. Frequently Asked Questions ❓
❓ Q: What is the essential difference between locking pliers and ordinary pliers?
A: Locking pliers use a toggle/cam mechanism to self-lock and hold the clamping force after the jaws close, enabling hands-free work, while ordinary pliers maintain grip only while the handles are squeezed.
A: Locking pliers use a toggle/cam mechanism to self-lock and hold the clamping force after the jaws close, enabling hands-free work, while ordinary pliers maintain grip only while the handles are squeezed.
❓ Q: Why does this edition emphasize “any material meeting performance”?
A: The Standard moved from designated material grades to performance-based acceptance, allowing new materials such as aluminum alloys and high-strength engineering plastics as long as the product passes the prescribed locking load and functional tests — opening the door to material innovation.
A: The Standard moved from designated material grades to performance-based acceptance, allowing new materials such as aluminum alloys and high-strength engineering plastics as long as the product passes the prescribed locking load and functional tests — opening the door to material innovation.
❓ Q: Can tubing pinch-off pliers be used on hard metal tubing?
A: No. Type II pinch-off pliers are designed for rubber or soft copper tubing, with jaw travel limited by a stop to protect the tube wall; hard metal lines require proper tubing tools, not pliers.
A: No. Type II pinch-off pliers are designed for rubber or soft copper tubing, with jaw travel limited by a stop to protect the tube wall; hard metal lines require proper tubing tools, not pliers.
🔍 Q: How do I evaluate whether locking pliers are compliant?
A: Check three points: the jaws hold firmly without wobble when locked; the adjustment mechanism runs smoothly with adequate range; and the release trigger operates easily at both full and minimum openings. If possible, run the B107.25M locking load test.
A: Check three points: the jaws hold firmly without wobble when locked; the adjustment mechanism runs smoothly with adequate range; and the release trigger operates easily at both full and minimum openings. If possible, run the B107.25M locking load test.
