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ASME B107.6-1994 — Wrenches, Box, Open End, Combination and Engineers (Inch Series)
🔧 ASME B107.6-1994 is the ASME B107 family standard for fixed wrenches in the inch (U.S. Customary) series, covering box wrenches, open-end wrenches, combination wrenches, and engineers wrenches. It is the primary reference for the dimensions and performance of this “fixed wrench” category in mechanical maintenance, automotive service, and industrial assembly, and is a companion to the metric-series standard ASME B107.9M. The Standard was developed by the ASME B107 Committee and approved as an American National Standard.
💡 Compared with the metric counterpart B107.9M, B107.6 expresses all dimensions in inch units; sizes in U.S. tooling typically progress as 1/4, 5/16, 3/8, 7/16, 1/2, 9/16, 5/8 in, and so on.
1. Scope and Product Classification 📌
The Standard provides complete general and dimensional data for the four wrench categories above. As with other B107 standards, dimensional data do not imply that all products are stock production sizes — consumers should consult manufacturers for production-size lists. Wrenches are grouped by Type, Class, and Style, with specified head opening offsets:
- Type I — Box wrench: double-head closed design, typically 15° offset at each end, in regular- and short-length classes; some styles carry deep or modified offset.
- Type II — Engineers wrench: double-head open-end design with each opening offset 15° from the handle, allowing flip-over use.
- Type III — Combination wrench: one open end and one 15°-offset box end, in regular, short, and long styles — the most widely used general-purpose configuration.
⚠️ The head offset angle (15°, 30°, 60°, etc.) governs both accessibility and torque application: larger offsets clear obstacles more easily, but the open end must still fully seat on the fastener head for proper engagement.
2. Technical Requirements and Specifications 📏
The Standard tabulates opening sizes, head thickness, overall lengths, head contours, and offset angles for every type, together with requirements for material, hardness, marking, and surface quality. The table below summarizes the typical characteristics of each class covered by B107.6:
| Type | Head Configuration | Offset Angle | Length Class | Typical Application |
|---|---|---|---|---|
| Type I Box | Double-head closed (12-pt) | 15° each end | Regular / Short | High-torque, slip-resistant tightening |
| Type I Deep-offset box | Double-head closed | Deep or modified offset | Regular / Short | Clearing obstructions, deep-recess work |
| Type II Engineers | Double-head open end | 15° | Fixed length series | Rapid run-up and general open-end turning |
| Type III Combination | Open end + box end | Open end / box 15° | Regular / Short / Long | General service: fast run-up, then torque up on box end |
On materials and heat treatment, the Standard requires wrenches to be heat treated to a specified hardness range, with openings conforming to the wrench-opening gages of ASME B107.17M — the “GO” gage must pass and the “NO GO” gage must be rejected. All external surfaces shall be cleaned, free from cracks, and essentially free from burrs, pits, nodules, and other detrimental defects, then finished against corrosion as prescribed.
3. Test Procedures and Quality Control 🔬
- Hardness test: performed per ASTM E18 (Rockwell); surfaces must be properly prepared and plating removed before testing.
- Proof-load test: a proof torque is applied in the defined fixture; the wrench must withstand it without failure or permanent deformation affecting durability or serviceability.
- Surface and coating inspection: visual and gage checks for external defects and coating quality.
🚨 Proof-load tests must be run with the correct fixture and loading location — box ends on the test mandrel, open ends held at the defined position. Loading with an over-length cheater bar beyond the specified lever arm invalidates the result and can destroy the tool.
4. Engineering Practice Essentials 🛠️
- 🔍 Selection: choose box wrenches for high torque and slip resistance; use open ends for fast run-up; pick short or deep-offset styles in confined spaces.
- 🔧 Size matching: the opening must match the fastener across-flats dimension exactly; never mix inch wrenches with metric fasteners.
- 📊 Technique: seat the wrench fully before applying force; pull rather than push where possible to protect the knuckles, and respect the manufacturer’s cheater-bar guidance.
- 📋 Care: clean and oil after use, inspect heads for cracks and spreading, and retire damaged tools immediately.
Beyond the types themselves, correct wrench selection also depends on the service duty. For continuous industrial use, forged alloy-steel wrenches with a full heat treatment give the best combination of strength and durability; for occasional home use, lighter constructions may be adequate but should still conform to the hardness and opening tolerances of the Standard. Because B107.6 is dimensioned in inches, care is required when building an international tool crib: keep inch and metric wrenches clearly separated in storage so that a 1/2 in wrench is never mistaken for a 13 mm unit, which would slip or jam on the wrong fastener.
5. Frequently Asked Questions ❓
❓ Q: How do B107.6 and B107.9M relate?
A: They are the inch- and metric-series versions of the same fixed-wrench families: B107.6 is dimensioned in inches, B107.9M in millimeters. Choose per the fastener system in use.
A: They are the inch- and metric-series versions of the same fixed-wrench families: B107.6 is dimensioned in inches, B107.9M in millimeters. Choose per the fastener system in use.
❓ Q: Why does a combination wrench have one open end and one box end?
A: The open end allows fast placement and removal (especially on long threads), while the box end provides full 6- or 12-point engagement with higher torque and less slip — combining speed and reliability.
A: The open end allows fast placement and removal (especially on long threads), while the box end provides full 6- or 12-point engagement with higher torque and less slip — combining speed and reliability.
🔍 Q: What is the purpose of the 15° offset?
A: It lets you change the turning direction by flipping the wrench 180° in confined spaces, improving reach; deeper offsets add obstacle clearance.
A: It lets you change the turning direction by flipping the wrench 180° in confined spaces, improving reach; deeper offsets add obstacle clearance.
🔧 Q: Can I keep using a wrench whose head has spread slightly?
A: No. Spreading causes partial engagement, slipping, and possible fracture — it damages the fastener and risks injury. Re-verify dimensions and proof loads; discard out-of-tolerance tools.
A: No. Spreading causes partial engagement, slipping, and possible fracture — it damages the fastener and risks injury. Re-verify dimensions and proof loads; discard out-of-tolerance tools.
📋 Q: How should an inspection program treat a mixed inch/metric tool crib?
A: Verify every wrench against the B107.17M setting gages, mark inch and metric tools separately, and audit markings so that a worn inch opening cannot be mistaken for a nominal metric size. Retain proof-load and hardness records for critical tooling, and recheck wrench heads whenever a fastener shows corner rounding or galling during assembly.
A: Verify every wrench against the B107.17M setting gages, mark inch and metric tools separately, and audit markings so that a worn inch opening cannot be mistaken for a nominal metric size. Retain proof-load and hardness records for critical tooling, and recheck wrench heads whenever a fastener shows corner rounding or galling during assembly.
