ASME B94.5-1974 — Carbide Blanks and Single-Point Brazed Tools

28 10 月, 2026
ASME Standards

🛠️ ASME B94.5-1974 is the American National Standard covering the designations, shapes, and dimensional specifications of carbide blanks and single-point carbide tools. Its history goes back to ASA B5.22-1950 (Single-Point Tools and Tool Posts); the carbide tooling portion was approved as ASA B5.36 on November 18, 1957, revised as B94.5-1966 on January 21, 1966, and approved in its current form by the American National Standards Institute on June 6, 1974. The Standard covers two product categories: sintered carbide blanks for making solid or tipped cutting tools, and finished single-point carbide tools (turning, boring, etc.) with carbide tips brazed to a steel shank.

💡 The blank–tool system: a blank is an unground carbide solid; toolmakers grind finished tips from it and braze them to a shank to form a complete tool. Standardized blanks let different tool manufacturers use common stock and interchangeable processes, cutting the cost of diverse tip geometries.

1. Scope, Definitions, and General 📌

Clause 1 states the Standard covers designations, shapes, and dimensional specifications of carbide blanks and single-point carbide tools. Clause 2 definitions:

Carbide: a sintered carbide of refractory metals, suitable as a cutting material;
Blank: an unground carbide solid from which a solid or tipped cutting tool can be made;
Tip: a blank brazed on a shank to form a cutting tool.

Figure 1 of the Standard illustrates a typical single-point carbide-tipped tool and its elements: End Cutting Edge Angle (ECEA), overall length, side clearance angle, tip thickness, tip overhang, end relief angle, and end clearance. Importantly, side rake, side relief, and clearance angles are measured normal to the side cutting edge rather than to the shank, to facilitate grinding on a tilting-table grinder; end relief and clearance are normal to the end cutting edge; the back rake angle is parallel to the side cutting edge.

⚠️ Angle datum is the cutting edge, not the shank: single-point tool angles are defined by the cutting geometry. If you measure or grind against the shank axis you will get wrong values — always follow the Standard’s convention.

2. Sintered Carbide Blank Styles and Identification 📦

Clause 3 specifies eight styles of sintered carbide blanks, identified by a four-digit number: the first digit designates the style; the other three digits designate a specific size (the numbers carry no implicit code or relationship, being sequential references). The eight styles cover the basic geometries needed to make turning, boring, and planing single-point tools.

Style (1st digit)	Blank Shape	Typical Use
1 series	Square/rectangular block	General turning tool tips
2 series	Rectangular bar	Straight turning and parting tool tips
3 series	Angled/symmetrical diamond block	45° angled turning tool tips
4 series	Thick rectangular block	Rough and heavy turning tips
5 series	Round bar	Round boring bar tips
6 series	Square bar	Square boring bar tips
7 series	Special/profile	Form and special-purpose tool tips
8 series	Extra-thick / large	Large special-purpose tips

💡 A four-digit number denotes “style + size”: e.g., 1xxx is Style 1. Select the blank by first deciding the tool profile (solid or tipped, turning or boring), then by the grinding allowance needed to develop the finished tip without grinding through.

3. Brazed Single-Point Tool Series 🔧

Clause 4 covers “Sintered Carbide Tipped General Purpose Tools” — finished single-point carbide tools, including:

Finished single-point carbide turning tools (Style D): square/rectangular shanks, right-hand tools;
Solid carbide square boring tools: bodies entirely of carbide;
Carbide-tipped square boring tools: steel bodies with brazed carbide tips;
Solid carbide round boring tools;
Carbide-tipped round boring tools;
Carbide-tipped round general purpose square end boring tools, etc.

Tool Category	Shank Shape	Construction	Typical Application
Right-hand turning tool	Square/rectangular	Brazed tip	External turning, facing, shoulders
Square boring tool	Square-section bar	Solid or tipped	Boring internal square/keyways side
Round boring tool	Round-section bar	Solid or tipped	Boring cylindrical holes, internal chamfers
General purpose square end round boring tool	Round-section bar	Brazed tip	Bore-mouth facing, countersink

⚠️ Boring bars are long and slender — rigidity is the primary constraint. The overhang ratio (stick-out to bar diameter) should generally not exceed 4:1; for deeper holes choose a larger bar or a damped boring bar, or vibration will quickly chip the edge.

4. Boring Tool Styles and Bar Angles 🔄

The Standard classifies boring tools by lead (bar) angle:

90° boring tools: for square shoulders and bottom planes;
60° boring tools: for bore-mouth chamfers and taper rough boring;
45° boring tools: for large chamfers, faces, and transition surfaces.

Styles such as SRC/SRE may also specify rake angle: 0° rake strengthens the edge for cast iron and interrupted cuts, while 10° rake cuts more freely for continuous steel turning.

💡 Naming logic: e.g., “Style SSC (for 60° Boring Bar)” and “Style TSA (for 90° Boring Bar)” — S/T denote the square/triangle tip profile and the following letters distinguish bar angle and rake combinations. Look up the standard by hole type and lead angle to fix the style.

5. Engineering Practice Essentials 🛠️

🔍 Blank selection: determine the blank number in three steps — finished tip size, plus grinding allowance (typically 0.5–1.0 mm per face), plus shank mounting size;
🔥 Brazing process: use silver- or copper-based filler, heat evenly, control temperature (about 700–900 °C) to avoid over-burning and thermal cracks; cool slowly after brazing and temper;
📐 Grinding geometry: grind side rake, side relief, and end relief on a tilting-table grinder per the Standard, keeping the two edges symmetric; after grinding, deburr and hone a 0.02–0.05 mm edge chamfer for edge strength;
🧪 Inspection: recheck angles with a protractor or projector and confirm braze bond coverage between tip and shank (typically no less than 70%);
📋 Management: record blank number, finished grinding parameters, and work station per tool for resharpening and traceability.

🚨 Brazed carbide tips carry high internal stress: rapid cooling or residual oxide at the braze interface creates micro-cracks in the tip that appear as chipping in service. Always cool slowly after brazing and verify the first part with conservative cutting conditions before raising speeds.

6. Frequently Asked Questions ❓

❓ Q: How do I choose between solid carbide and carbide-tipped boring bars?
A: Solid carbide bars are stiffer and can be ground to more complex edges, suiting small-diameter precision boring; tipped bars have steel bodies — lower cost, better toughness — suiting larger diameters and heavier boring, with replaceable/rebrazable tips.

❓ Q: What do the digits in a blank number mean?
A: The first digit indicates the blank style (eight styles in total); the remaining three are sequential size references with no implicit meaning. Select by looking up the length, width, and thickness in the Standard’s size tables.

❓ Q: Why is side clearance measured normal to the side cutting edge?
A: Grinding is done on a tilting-table grinder: the table is tilted so the wheel feeds normal to the cutting edge to produce the correct relief; measuring against the shank axis yields smaller actual angles. The Standard adopts this datum to unify manufacturing and inspection.

🔍 Q: How does B94.5 relate to the later indexable insert standards?
A: B94.5 is the classic standard for brazed single-point tools; as indexable inserts spread, standards such as B94.4 and B94.26 took over insert identification and holder specifications. Brazed tooling still serves heavy roughing, form turning, and repair work.

ASME B94.5-1974.pdf