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ASME B107.16M-1998 (2004) — Shears (Metal Cutting, Hand)
✂️ ASME B107.16M-1998 (2004) is the dedicated standard for hand-operated metal-cutting shears within the ASME B107 family of standards for hand tools and accessories. It establishes dimensions, design, material, identification-marking, and finish requirements for tinner’s shears and compound-lever (aviation) snips, together with complete test procedures such as the paper cutting test, metal cutting tests, wear tests for Type II shears, a comfort-grip solvent test, and a design qualification test. Approved as an American National Standard on April 3, 1998, it was reaffirmed in 2004 (REAFFIRMED 2004).
💡 The “M” in the designation indicates a dual-unit standard: dimensional tables give values in both inches (in.) and millimeters (mm), supporting global procurement and manufacturing.
1. Scope and General Framework 📌
The scope is precisely defined: the Standard covers hand shears used for cutting metal. The 1992 edition was titled Shears (Metal Cutting, Bench and Hand) and covered both bench-type and hand shears; the 1998 revision renamed the Standard to Shears (Metal Cutting, Hand), removed the Bench Type cutting shears, and revised the classification of the remaining shear types.
Two principal categories are prescribed:
- Type I — Tinner’s Shears: the sheet-metal worker’s straight snips for cutting thin steel sheet, tin plate, and similar material.
- Type II — Compound Lever (Aviation) Shears: snips with a compound-lever mechanism that multiplies cutting force, capable of straight and left/right circular cuts in thin sheet steel; widely used in sheet-metal work.
Normative references include ASME B46.1 (surface texture), ASTM A240/A240M and ASTM A366/A366M (sheet materials), and ASTM E18 (Rockwell hardness), which underpin the material and test provisions.
⚠️ This Standard addresses “hand” metal-cutting shears only. Bench shears, power shears, and machine tools are outside its scope; the dimensional and test provisions of B107.16M must not be applied to machine shearing equipment.
2. Classification 🔩
Hand metal-cutting shears are classified by type, class, style, and design:
- Type I — Tinner’S Shears
- Class 1 Straight Cut: Style A Heavy Duty, Style B Medium Duty
- Class 2 Circular Cut: Style A Heavy Duty, Style B Medium Duty
- Class 3 Duckbill (combination straight and circular cut)
- Type II — Compound Lever (Aviation) Shears
- Class 1 Straight Cutting
- Class 2 Circular Cutting to the Right
- Class 3 Circular Cutting to the Left
- Class 4 Offset Jaw Straight and Circular Cutting to the Right
- Class 5 Offset Jaw Straight and Circular Cutting to the Left
3. Technical Requirements and Specifications 📊
The Standard provides inch and millimeter dimension tables for the key geometric parameters of the shears (overall length, length of cut, blade geometry, and jaw form) and imposes material, hardness, and finish requirements. Typical parameters are shown below:
| Parameter | Type I Tinner (Example) | Type II Aviation (Example) |
|---|---|---|
| Overall length | 6 in (152 mm) to 12 in (305 mm) series | 7 in to 12 in (178–305 mm) series |
| Length of cut | Straight cut about 1.75 in | Varies by class |
| Blade/jaw configuration | Straight, circular, or duckbill | Straight, left/right circular, offset jaw |
| Material | Carbon sheet steel, stainless steel (per ASTM references) | Alloy steel, forged blades hardened |
| Hardness | Blade area heat-treated to Rockwell (RC) requirements | Cutting edges hardened for service life |
| Finish | Corrosion-resistant plating or blackening | Rust protection; optional comfort grips |
The test methods constitute a complete performance-verification program:
- Paper Cutting Test: verifies edge uniformity and sharpness along the full length of the blade.
- Metal Cutting Tests: continuous cutting through a prescribed sheet thickness to verify cutting capacity and blade condition.
- Wear Tests for Type II: cumulative cutting to verify edge wear life.
- Comfort Grips Solvent Test: verifies grip material resistance to solvents.
- Design Qualification Test: overall qualification of a new product design before production.
🚨 Hardness and toughness must be balanced: excessive hardness causes chipping while insufficient hardness rolls the edge and shortens life. Acceptance should combine hardness checks with paper and metal cutting tests, never appearance alone.
4. Engineering Practice Essentials 🛠️
- 🔍 Select by job: use Class 2/3 (left/right) aviation snips for curved cuts and offset-jaw classes (4/5) for confined or offset work; choose tinner’s shears for everyday thin-sheet cutting.
- ⚠️ Respect cutting capacity: every snip has a designed maximum sheet thickness; forcing more thickness chips the blades, damages the hinge, and risks hand injury.
- 🔧 Maintenance: clean blades after use, remove metal filings, and apply rust-preventive oil; lubricate and keep the hinge tensioned to prevent blade gap.
- 📋 Marking: the Standard requires marking the manufacturer’s name or trademark and the corresponding designation; list the complete designation in purchasing documents for traceability.
- 📅 Edge care: inspect the edges for chips and rolls periodically; light dulling may be resharpened professionally without changing the designed blade geometry.
5. Frequently Asked Questions ❓
❓ Q: Why is a paper cutting test required?
A: Paper cutting sensitively reveals edge conformity and sharpness along the full blade length — a fast, inexpensive functional check. Passing a metal test alone does not guarantee edge conformity; the two tests complement each other.
A: Paper cutting sensitively reveals edge conformity and sharpness along the full blade length — a fast, inexpensive functional check. Passing a metal test alone does not guarantee edge conformity; the two tests complement each other.
❓ Q: Can aviation snips cut stainless steel?
A: It depends on the designed capacity. Most aviation snips are designed for thin plain-carbon sheet (about 18 to 24 gauge). Stainless steel is stronger; check the specified maximum cut thickness and material limits, or the blades will be damaged.
A: It depends on the designed capacity. Most aviation snips are designed for thin plain-carbon sheet (about 18 to 24 gauge). Stainless steel is stronger; check the specified maximum cut thickness and material limits, or the blades will be damaged.
❓ Q: What changed versus the older B107.16-1992?
A: The principal change was retitling the Standard to “hand” metal-cutting shears and removing the bench-type cutting shears, plus a revised classification; the 2004 reaffirmation confirmed the 1998 text without content changes.
A: The principal change was retitling the Standard to “hand” metal-cutting shears and removing the bench-type cutting shears, plus a revised classification; the 2004 reaffirmation confirmed the 1998 text without content changes.
🔍 Q: What if the blades slip or chip during cutting?
A: Stop immediately and inspect: a chipped edge accelerates further damage and makes cutting paths unpredictable. Do not continue using chipped shears; handle per the manufacturer’s repair policy or replace them.
A: Stop immediately and inspect: a chipped edge accelerates further damage and makes cutting paths unpredictable. Do not continue using chipped shears; handle per the manufacturer’s repair policy or replace them.
