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ASME B94.14.1-1977 — Punches — Basic Head Type (Metric)
🔩 ASME B94.14.1-1977 (ANSI B94.14.1-1977) is the metric (SI) companion to the inch-standard USAS B94.14-1968 for basic head type punches, prepared with the National Association of Punch Manufacturers (NAPM) as principal collaborator. The Standard organizes the shank, head, and point dimensions and tolerances of headed punches entirely in millimeters, serving markets outside North America and metric-converted plants that build metric stamping tooling. As with the inch edition, it covers perforating punches and pilot punches of headed type, providing the dimensional basis for punch interchange and rapid replacement in metric dies. It is the metric representative of the B94 “interchangeable punches and accessories” series, complementing the metric ball-lock retainers (B94.16.1) and metric functional gages (B94.17.1) to form a complete metric die-standard portfolio.
💡 In metric countries (China, Europe, Japan), B94.14.1 gives die designers an “off-the-shelf” headed punch series: choose a shank diameter and point diameter, and the supplier delivers to standard — punches interchange in die maintenance with no fitting required.
1. Scope and Position of the Standard 📌
This Standard defines metric dimensional specifications, types, and designation for basic head type punches. It covers shank diameter and length series, head diameter and thickness, point diameter grading and point lengths, overall length, and associated tolerances and surface requirements. The subject matter is perforating and pilot punches of headed type in precision stamping dies, organized — like the inch edition — around the shank diameter (the retainer bore) as the primary size axis.
⚠️ The metric and inch editions are two parallel systems, not one-to-one conversions: metric dimensions are rounded to preferred-number series in millimeters rather than exact conversions of inch values. A shop maintaining both metric and inch product lines must never mix values from the two tables.
2. Metric Dimensional Series 📏
The metric series is organized by shank diameter. A representative series (illustrative values; consult the Standard’s tables for exact figures):
| Shank Dia. (mm) | Point Dia. Range (mm) | Head Dia. (mm) | Typical Application |
|---|---|---|---|
| 3.175 (1/8 in.) | 0.8–2.0 | ≈6.4 | Thin-stock micro perforating |
| 6.35 (1/4 in.) | 1.6–4.8 | ≈9.5 | General perforating |
| 9.525 (3/8 in.) | 2.4–7.1 | ≈12.7 | Medium-stock perforating |
| 12.7 (1/2 in.) | 3.2–10.3 | ≈15.9 | Heavy stock, large holes |
| 19.05 (3/4 in.) | As required | ≈22.2 | Rough punching, heavy blanking |
The metric Standard retains the core fit philosophy of the inch edition: the shank and retainer bore use a precision close-clearance fit (H7/g6 order in millimeter terms), the point diameter is selected for the hole being cut with allowance for die clearance, and limits are placed on point-to-shank concentricity and point length range to secure regrind life and stamping stability.
🚨 A metric punch’s “nominal” shank size may be a whole millimeter (e.g., 6 mm or 10 mm) or an inch-barstock conversion (e.g., 6.35 mm or 12.7 mm). Always verify the actual millimeter value in the Standard table for that size step; otherwise the retainer bore will carry a systematic error.
3. Designation and Marking Rules 🔤
Metric punches are typically designated by “shank × point × point length” or by a standard code plus size digits. The Standard stresses that a designation must carry complete dimensional information and state the unit system (Metric) explicitly. The die drawing, purchase order, and punch engraving must agree to avoid costly unit mix-ups in assembly.
💡 Pairing with the inch edition: if one die uses both metric and inch standard parts (e.g., an inch retainer with a metric punch), confirm the retainer bore versus punch shank first; a metric punch cannot be mounted into an inch bore unless that bore converts exactly to a standard metric shank.
4. Engineering Practice Essentials 🛠️
- 🔍 Metric design workflow: define hole size (mm) and stock thickness → set point diameter from die clearance (5%–10% of thickness) → choose point length for regrind allowance → select shank from the retainer bore → verify head against the counterbore/retainer.
- 🔧 Installation: seat the head in the holder counterbore and clamp with a retainer plate; machine the holder bore and head counterbore in one setup to keep them concentric and avoid punch misload.
- 📊 Grinding and life: metric point length also reserves multiple regrinds; log each regrind amount and scrap the punch at minimum length. Build a punch life ledger by regrind count.
- 📋 Supplier consistency: procure from suppliers building to B94.14.1 and request dimensional inspection reports and material certificates; sample-check shank, head, and concentricity on incoming lots.
5. Frequently Asked Questions ❓
❓ Q: Can B94.14.1 and B94.14 (inch) be substituted?
A: Not directly. The subjects are the same but the dimensioning differs; unless the retainer bore happens to match the metric shank exactly, choose punches and retainers from one system as a set.
A: Not directly. The subjects are the same but the dimensioning differs; unless the retainer bore happens to match the metric shank exactly, choose punches and retainers from one system as a set.
❓ Q: How does the metric point diameter mate with the die?
A: As in the inch series, the point diameter follows the clearance rule (generally 5%–10% of stock thickness) and must be smaller than the die bore by that amount; the Standard gives a point-diameter range and the final diameter is ground at assembly.
A: As in the inch series, the point diameter follows the clearance rule (generally 5%–10% of stock thickness) and must be smaller than the die bore by that amount; the Standard gives a point-diameter range and the final diameter is ground at assembly.
❓ Q: Which dies use metric headed punches?
A: Punching, blanking, compound, and progressive dies for perforating and pilot stations, plus multi-station transfer dies needing rapid punch change. For ball-lock retention, use the B94.18 family (including its metric counterparts).
A: Punching, blanking, compound, and progressive dies for perforating and pilot stations, plus multi-station transfer dies needing rapid punch change. For ball-lock retention, use the B94.18 family (including its metric counterparts).
❓ Q: Why is a shank 6.35 mm rather than 6 mm?
A: 6.35 mm is the exact conversion of 1/4 in. for compatibility with inch bar stock and tooling; the Standard also offers pure metric preferred-number sizes. Which one applies depends on whether the die uses an inch-barstock or a pure metric system.
A: 6.35 mm is the exact conversion of 1/4 in. for compatibility with inch bar stock and tooling; the Standard also offers pure metric preferred-number sizes. Which one applies depends on whether the die uses an inch-barstock or a pure metric system.
🔍 Q: What routine checks apply to metric headed punches?
A: Inspect point wear, point-to-shank concentricity, and the head bearing surface for indentation. Sample-check the shank and head on incoming lots, and re-verify at each regrind interval; replace any punch that shows concentricity loss or head deformation to prevent misload damage to the die and press.
A: Inspect point wear, point-to-shank concentricity, and the head bearing surface for indentation. Sample-check the shank and head on incoming lots, and re-verify at each regrind interval; replace any punch that shows concentricity loss or head deformation to prevent misload damage to the die and press.
