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ASME B94.27-1970 — Die Buttons: Basic Taper Relief, Press Fit
⭕ ANSI B94.27-1970 is the dedicated American National Standard for die buttons used in stamping dies. Its full title, “Die Buttons — Basic Taper Relief, Press Fit,” defines both the cutting-edge geometry (basic taper relief) and the mounting method (press fit). Published by ASME and developed in cooperation with the National Association of Punch Manufacturers (NAPM), it specifies types and dimensions for press-fit die buttons and is a key element of the standardized stamping tooling system that also includes ball-lock punches (B94.18) and punch guide bushings (B94.23). As the female cutting element that mates with the punch, a standardized die button guarantees cross-vendor interchangeability.
💡 The die button bore mates with the punch point to form the shear clearance. “Taper relief” means the wall below the cutting edge flares outward in a controlled taper, letting punched slugs discharge cleanly and self-align, while a short straight land preserves cutting accuracy and edge life.
1. Standard Theme and Structure 📌
The theme of this Standard is the standardization of press-fit die buttons. The body provides dimension tables for each button size, defining:
- Bore (mating with the punch) and the straight-land length.
- Taper relief angle and relief-section geometry.
- Outside-diameter press-fit section and overall length.
- Head/lead-in chamfer details for pressing and location.
⚠️ The button bore must match the punch point diameter and the desired die clearance. Standard buttons are graded by nominal bore size; the actual clearance is set by work material and thickness, so select the closest standard bore and finish the land to the target diameter.
2. Function and Construction 🔧
The die button performs the core shearing function in a stamping die:
- Shear land: the straight land at the top of the bore pairs with the punch to form the shearing pair that determines blanking-edge quality.
- Slug discharge: the taper-relief section guides slugs downward, preventing slug buildup and re-pull problems.
- Location and retention: the OD is pressed with interference into the die shoe, resisting the blanking reaction force.
🚨 Never grind the relief section from inside a worn button — that destroys the relief angle and land geometry, causing slug hang-up and degraded edges. When the land fails, replace the button wholesale with a standard size.
3. Dimensional and Fit System 📏
| Design Element | Description | Engineering Role |
|---|---|---|
| Bore (land) | Graded by punch diameter, with straight land height | Sets die clearance and blanking quality |
| Taper relief angle | Standard relief angle, ~1/2°–1° order | Clean slug discharge, anti-stick |
| OD press-fit section | Interference fit in the shoe bore | Retains the button, carries blanking force |
| Overall length and head | Selected by shoe thickness, with chamfer/step | Axial location and press-in guidance |
💡 Press-fit buttons are individually replaceable and easy to manage: the shoe needs only standard through-holes, and different bore sizes are obtained by swapping button grades — giving multi-hole dies flexibility and fast maintenance.
4. Materials and Heat Treatment 🛠️
Die buttons are normally made of wear-resistant tool steels hardened overall. Common choices include:
- High-carbon, high-chromium cold-work die steel (D2-type): excellent wear resistance for medium-to-high volume blanking.
- Bearing steel (52100-type): cost-effective for general blanking.
- Powder-metal high-speed steel or carbide: for ultra-high life and high-speed blanking duties.
💡 Button bores are usually internal-ground or honed to guarantee roundness and surface finish of the land. Matching hardness with the punch point gives even wear and longer regrind intervals.
5. Engineering Practice Essentials 📋
- 🔍 Selection workflow: derive the bore from punch diameter plus clearance → pick the standard bore grade → select overall length from shoe thickness → verify press-fit interference and shoe-hole tolerance.
- 🔨 Pressing: press the button into the shoe bore with a press, keeping it vertical; use a pilot pin if needed to protect the land.
- 🔧 Clearance check: after mounting, verify the actual clearance distribution between punch and button with shim stock or a gage.
- 📏 Wear maintenance: measure land wear periodically and set replacement thresholds; check the button land first whenever burr growth appears.
6. Frequently Asked Questions ❓
❓ Q: What is “taper relief”?
A: It is the conical flare of the button bore below the cutting edge. Punched slugs discharge cleanly and self-align through the taper, while the short straight land preserves blanking accuracy.
A: It is the conical flare of the button bore below the cutting edge. Punched slugs discharge cleanly and self-align through the taper, while the short straight land preserves blanking accuracy.
❓ Q: How are button bore and punch diameter related?
A: Button bore = punch diameter + total (both sides) die clearance; clearance is typically 3%–8% of stock thickness depending on material. Pick the closest standard bore grade and finish to the target dimension.
A: Button bore = punch diameter + total (both sides) die clearance; clearance is typically 3%–8% of stock thickness depending on material. Pick the closest standard bore grade and finish to the target dimension.
❓ Q: Why replace a worn button rather than repair it?
A: Because reworking the relief destroys the relief geometry and shortens life, whereas replacing with the same standard grade restores accuracy quickly and keeps all lands in a multi-station die consistent.
A: Because reworking the relief destroys the relief geometry and shortens life, whereas replacing with the same standard grade restores accuracy quickly and keeps all lands in a multi-station die consistent.
🔍 Q: How does this Standard relate to B94.27.1M-1983?
A: B94.27-1970 is the inch (U.S. Customary) edition; B94.27.1M-1983 is the metric (SI) edition of the same content, so users can choose the units system most convenient for their drawings and toolroom.
A: B94.27-1970 is the inch (U.S. Customary) edition; B94.27.1M-1983 is the metric (SI) edition of the same content, so users can choose the units system most convenient for their drawings and toolroom.
