Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
ASME B94.13-1976 — Blanks for Carbide Burs
🔧 ASME B94.13-1976 (ANSI B94.13-1976) is the American National Standard for standard blanks for carbide burs, developed by the Cemented Carbide Producers Association in cooperation with the Solid Carbide Tool Institute and maintained by Technical Committee 1 of American National Standards Committee B94. A carbide bur is a small, high-speed solid carbide rotary cutter used for die rework, deburring, chamfering, and shaped-surface finishing. The Standard defines dimensional specifications and designations for twelve standard blank shapes — cylindrical, ball-nose cylinder, ball, olive, tree, flame, cone, and inverted-cone forms in diameters from 1/4 in. to 1 in. and lengths up to 1 in. — creating a common dimensional language between blank producers and bur manufacturers. The lineage goes back to a 1959 proposal by the Cemented Carbide Producers Association approved as an American Standard in 1962, incorporated into the B94 series in 1968, and revised a second time in 1976.
💡 Bur blanks are semi-finished products: a standard-shaped carbide solid is produced by powder metallurgy, then the bur maker grinds the cutting teeth and attaches a shank to form the finished bur. Standardized blank shapes let different makers share the same sintering tooling, cutting cost and ensuring consistent quality.
1. Scope and Definitions 📌
Chapter 1 states: this Standard covers dimensional specifications and designations for standard blanks for carbide burs. Chapter 2 gives the definitions:
- Carbide: a sintered material of refractory metal suitable for use as a cutting tool.
- Blank: an unground carbide solid.
Chapter 3, the “Identification System,” groups blanks by shape, each class covered by its own dimension table. Appendix A provides inch-to-millimeter conversion tables.
⚠️ B94.13 specifies blanks, not finished burs. The Standard gives the sintered body shape and dimensions; teeth and shank are finished by the manufacturer. When purchasing finished burs, do not reference these tables — use finished-product standards or manufacturer catalogs.
2. Shape Classification and Designation System 🔤
The identification system names blank shapes with three letters — the leading B for Blank followed by two shape letters — and a size number whose actual dimensions are given in the corresponding table. The principal shapes covered are:
| Code | Shape | Typical Size Range | Typical Application |
|---|---|---|---|
| BSA / BSB | SA: cylindrical | 1/4×3/16 in. to 1×1 in. | Flat surfaces, bores, chamfers |
| BSC | SC: cylindrical ball nose | from 5/8×1/2 in. | Rounded edges, transitions |
| BSD | SD: ball | 1/4 in. to 1 in. diameter ball | Ball seats, concave surfaces |
| BSE | SE: olive | 1/4×3/8 in. to 1/4×1 in. | Narrow grooves, curved surfaces |
| BSF | SF: tree, radius nose | from 1/4 in. diameter | Cavities, die corner work |
| BSG | SG: tree, pointed nose | — | Sharp corners, deep slots |
| BSL | SL: 14-degree cone, ball nose | — | Chamfers, conical surfaces |
| BSM | SM: cone | — | Counterbores, cone dressing |
| BSN | SN: inverted cone | — | Bottom corners, reverse cones |
| BSJ / BSK | SJ: 16-degree cone; SK: 90-degree cone | — | Special conical work |
💡 Example designations: BSD-1 is size-1 ball blank (1/4-inch diameter ball); BSE-3 is size-3 olive blank (1/4-inch diameter × 3/8-inch long). Always give code plus size number on the order — a shape name alone cannot fix the dimensions.
3. Dimensional Requirements 📏
Tables 1 through 12 give the dimensions for each shape: cylindrical blanks list diameter, length, and tolerances; ball blanks list ball diameter; olive, tree, flame, and cone forms list maximum diameter, overall length, and transition profile. Beyond dimensions, blanks must meet sintering quality requirements — uniform density, no cracks or inclusions — so that subsequent tooth grinding produces complete, durable edges.
Note that the SA shape uses two codes, BSA and BSB: the shapes are identical but size ranges or tolerance grades differ, so follow the table notes. Specialty shapes such as the flame form serve die-cavity polishing and depend more heavily on a given maker’s tooling series.
🚨 Blank dimensional tolerance directly controls finished-bur concentricity and tooth-wall uniformity: uneven tooth thickness causes vibration and chipping at high speed. On acceptance, check both profile dimensions and sintered density — do not rely on maximum diameter alone.
4. Engineering Practice Essentials 🛠️
- 🔍 Shape selection: cylinders (SA/SC) for flats and bores, ball (SD) for ball seats and concave work, olive (SE) for narrow grooves and curves, tree (SF/SG) for die cornering, cones (SM/SL) for chamfers and counterbores. The blank shape dictates the finished bur’s profiling capability.
- 🔧 Tooth grinding: tooth form (helix, tooth count, indexing) is the maker’s design, but tooth depth must stay within the sintered wall thickness to avoid grinding through and causing thin-wall cracking.
- 📊 Shank assembly: finished burs join the ground end to a steel shank by brazing or press-fitting; assembly concentricity should be on the order of 0.05 mm or better, or high-speed runout becomes excessive.
- 📋 Traceability: request carbide grade (WC-Co composition) and sintering batch records so hardness and toughness match the work material, such as die steel or stainless steel.
5. Frequently Asked Questions ❓
❓ Q: Why make bur blanks first and grind teeth later, instead of sintering finished burs?
A: Sintering shrinkage is hard to control, so directly sintered teeth lack precision and sharpness. Sintering a standard blank with grinding stock and then cutting teeth with diamond wheels yields sharp, uniform, dimensionally accurate products — and standardized blanks let makers share tooling.
A: Sintering shrinkage is hard to control, so directly sintered teeth lack precision and sharpness. Sintering a standard blank with grinding stock and then cutting teeth with diamond wheels yields sharp, uniform, dimensionally accurate products — and standardized blanks let makers share tooling.
❓ Q: How does B94.13 differ from B94.20 (carbide blanks for cutting tools)?
A: B94.13 specifically covers bur blank shapes (cylinder, ball, olive, tree, etc.); B94.20 covers bar/rod blanks for twist drills, reamers, and end mills. The two are divided by tool type.
A: B94.13 specifically covers bur blank shapes (cylinder, ball, olive, tree, etc.); B94.20 covers bar/rod blanks for twist drills, reamers, and end mills. The two are divided by tool type.
❓ Q: Can a user grind teeth into bur blanks themselves?
A: Technically yes, but it requires diamond wheels, precision grinders, and specialized processes (tooth development, indexing, relief). For almost all users, buying finished burs made from standard blanks is more economical and reliable.
A: Technically yes, but it requires diamond wheels, precision grinders, and specialized processes (tooth development, indexing, relief). For almost all users, buying finished burs made from standard blanks is more economical and reliable.
❓ Q: Why does the Standard stop at 1 in. diameter?
A: Burs are mainly used for die rework and finishing, where sizes concentrate between 1/4 and 1 in. Larger diameters carry high torque and see little demand; they are supplied by makers as non-standard or dedicated series.
A: Burs are mainly used for die rework and finishing, where sizes concentrate between 1/4 and 1 in. Larger diameters carry high torque and see little demand; they are supplied by makers as non-standard or dedicated series.
