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ASME B94.12-1977 — Carbide-Tipped Masonry Drills and Blanks for Carbide-Tipped Masonry Drills
🏗️ ASME B94.12-1977 (ANSI B94.12-1977) is the American National Standard for carbide-tipped masonry drills and blanks for carbide-tipped masonry drills, prepared under the ASME Secretariat by Technical Committee 1 (Carbide and Oxide Tools) of American National Standards Committee B94 (Standardization of Cutting Tools, Holders, Drivers, and Bushings). The Standard covers dimensional specifications and designations for finished carbide-tipped masonry drills, blanks with grinding stock, and blanks without grinding stock. It is the purchasing and manufacturing basis for rotary-percussion drilling of brick, concrete, tile, and other hard nonmetallic materials. The Standard grew out of the Cemented Carbide Producers Association’s B82.1 of 1962, was incorporated into the B94 series as B94.12 in 1968, and was revised a second time in 1977.
💡 A masonry drill’s “tip” is a carbide cutting edge brazed or inset into a steel body for percussion drilling of concrete, brick, and stone. Compared with solid carbide drills, tipped drills combine the toughness of the steel body with the wear resistance of the carbide edge at lower cost.
1. Scope and Definitions 📌
Chapter 1 states: this Standard covers dimensional specifications and designations for carbide-tipped masonry drills and blanks for carbide-tipped masonry drills. Chapter 2 gives two essential definitions:
- Carbide: a sintered material of refractory metal suitable for use as a cutting tool.
- Blank: an unground carbide solid.
The three product categories are covered by three tables: Table 1 — carbide-tipped masonry drills; Table 2 — blanks with grinding stock; Table 3 — blanks without grinding stock. Appendix A provides inch-to-millimeter conversion tables.
⚠️ Flute form, tip shape, and relief angles of tipped masonry drills are left to manufacturer practice; only nominal diameter, body, and length must conform to the Standard so that chucks and fixtures remain interchangeable.
2. Designation System 🔤
The hallmark of the Standard is a compact designation system. The three product classes use the prefixes FMD, MD, and MDG followed by a number equal to the nominal drill diameter in sixteenths of an inch:
- FMD: Fluted Masonry Drill — e.g., FMD 3 denotes a fluted masonry drill with a 3/16-inch nominal diameter.
- MD: Blank with grinding stock (blank shape) — e.g., MD 3 denotes a 3/16-inch nominal-diameter blank.
- MDG: Blank without grinding stock (preformed blank shape) — e.g., MDG 3 denotes a 3/16-inch nominal-diameter preformed blank.
Table 1 lists nominal diameters from FMD 2 (1/8 in.) through FMD 24 (1-1/2 in.), including fractional-sixteenths series such as 2.5, 2.75, 3.25, 3.5, 3.75, and 3.88 (0.242 in.), plus “-1” variants (7-1, 8-1, 9-1) denoting extended-length forms of the same nominal sizes — over thirty designations in all.
| Prefix | Meaning | Example Nominal Diameter | Typical Use |
|---|---|---|---|
| FMD | Fluted Masonry Drill | FMD 3 = 3/16 in.; FMD 5 = 5/16 in. | Finished percussion drill, ready to use |
| MD | Blank with grinding stock | MD 3 = 3/16 in. | User grinds diameter and cutting edges |
| MDG | Blank without grinding stock | MDG 3 = 3/16 in. | Functional when mounted, no grinding |
💡 The number in the designation is “sixteenths of an inch,” not an ordinal size index: 3 means 3/16 in., 3.5 means 7/32 in., 3.75 means 15/64 in. Always verify the full designation on your purchase order.
3. Requirements for the Three Product Classes 📏
1. Carbide-tipped masonry drills (Table 1): nominal drill diameter, body diameter and tolerances, overall length, and shank dimensions are specified. Sizes such as 0.242 in. (designation 3.88) continue the decimal-inch drill tradition; the 7-1, 8-1, and 9-1 designations denote extended flute or shank forms of the same nominal sizes for deeper holes.
2. Blanks with grinding stock (Table 2): intended mainly for users who will grind the diameter and cutting edges to their own requirements. The blank is a sintered carbide solid with enough stock left for machining, so its outer dimension exceeds the final nominal diameter; material and shape are specified.
3. Blanks without grinding stock (Table 3): intended mainly for users who will mount them without grinding. The blank is preformed so that, when properly mounted (brazing, setting, or mechanical clamping), it is functional as-is — suited to large-scale assembly production.
🚨 MD (with grinding stock) and MDG (without grinding stock) blanks are not interchangeable: an MD blank carries machining allowance and will not yield a correct hole diameter if mounted directly; grinding an MDG blank can destroy the preformed edge geometry and carbide surface layer. Confirm whether your next operation is “grind” or “assemble” before ordering.
4. Engineering Practice Essentials 🛠️
- 🔍 Match drill body to chuck: masonry drill shanks are typically round; match the shank diameter to the hammer-drill chuck. The designation number (e.g., FMD 5 = 5/16 in.) is the cutting diameter, not the shank diameter — verify both on the order.
- 🔧 Percussion mode and speed: masonry drills cut by rotary percussion that fractures brittle material. Choose body construction consistent with the recommended impact energy and never treat a tipped drill as an ordinary metal-cutting drill in high-speed non-impact mode, which can break the carbide edge.
- 📊 Grinding management: for MD blanks, grind the diameter and edges symmetrically with correct clearance, avoiding lobing that causes hole wander; never regrind MDG blanks.
- 📋 Acceptance and marking: verify dimensions against Tables 1–3 and confirm that each designation matches its actual diameter; for batch purchases, request carbide grade and material certificates to ensure wear and impact resistance for the intended service.
5. Frequently Asked Questions ❓
❓ Q: What materials are covered by “masonry” in B94.12?
A: Brittle nonmetallic materials such as brick, concrete, block, stone, and tile. The carbide-tipped drill fractures these by impact; it is not for metal cutting.
A: Brittle nonmetallic materials such as brick, concrete, block, stone, and tile. The carbide-tipped drill fractures these by impact; it is not for metal cutting.
❓ Q: Both FMD and MDG can be used directly — what is the difference?
A: FMD is a complete finished drill (steel body + tipped carbide + flutes) ready to mount in a drilling machine; MDG is a “no-grinding” blank that still needs user finishing steps such as brazing or mounting before it becomes a finished drill. FMD targets end users; MDG targets drill manufacturers and assembly shops.
A: FMD is a complete finished drill (steel body + tipped carbide + flutes) ready to mount in a drilling machine; MDG is a “no-grinding” blank that still needs user finishing steps such as brazing or mounting before it becomes a finished drill. FMD targets end users; MDG targets drill manufacturers and assembly shops.
❓ Q: Why buy “grinding stock” blanks instead of finished drills?
A: Some users need non-standard diameters or special edge geometry (particular clearance angles, split points). Standard blanks provide a uniform sintered starting body with enough stock for customization and traceable material quality.
A: Some users need non-standard diameters or special edge geometry (particular clearance angles, split points). Standard blanks provide a uniform sintered starting body with enough stock for customization and traceable material quality.
❓ Q: Is the Standard inch-only?
A: The 1977 edition is dimensioned in inches, with inch-to-millimeter conversion tables in Appendix A for metric users. For metric-series drills, refer to manufacturer catalogs organized on the metric system or later metric standards.
A: The 1977 edition is dimensioned in inches, with inch-to-millimeter conversion tables in Appendix A for metric users. For metric-series drills, refer to manufacturer catalogs organized on the metric system or later metric standards.
