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ASME B18.7.1M-2007 (2012) — Metric General Purpose Semi-Tubular Rivets — Oval Head
🔗 ASME B18.7.1M-2007 (reaffirmed 2012) is the metric rivet standard in the ASME B18 fastener system, developed by Subcommittee 7 (Tubular and Split Rivets) and superseding the ANSI/ASME B18.7.1M-1984 (R2005) edition. The Standard provides complete general and dimensional data for oval head semi-tubular rivets for general purpose applications. A semi-tubular rivet has a straight hole (tubular section) at its shank end; during setting, the shank end rolls outward to form a head under the forming die, requiring far less force than a solid rivet and producing a clean, attractive joint. These rivets are suitable for joining metallic and nonmetallic materials or combinations thereof.
💡 Semi-tubular rivets are the workhorse of automated assembly lines: the tubular section drastically reduces the force needed to form the clinch, so a single automatic riveting machine can feed, position, and set parts at high speed — the primary fastening method in electronics, appliances, luggage, toys, and automotive component industries.
1. Scope and General Framework 📌
The Standard covers oval head semi-tubular rivets for general purpose use. Key technical requirements include:
- Semi-tubular rivets: shanks with straight holes, normally produced by extruding or drilling.
- Head style: only the oval head is standardized in this edition; the Committee has declared its intent to expand coverage to other head styles, tapered holes, full tubular rivets, and rivet caps as metric usage becomes apparent.
- Units: unless otherwise stated, all dimensions are in millimeters and apply before any coating; finished dimensions after plating or coating are as agreed between supplier and purchaser.
- Geometric tolerancing: symbols follow ASME Y14.5M.
Inclusion of dimensional data does not imply that all products are stock sizes; consult manufacturers for special-purpose types. No ISO standard for tubular rivets exists at this time.
⚠️ The depth of the tubular hole determines the clinch roll and the shear strength of the joint. Selection must match hole depth, shank length, and total workpiece thickness: too short a shank gives an incomplete clinch with insufficient strength; too long a shank leaves protruding material or damages thin panels after setting.
2. Technical Requirements and Size Data 🔧
| Parameter | Requirement / Description | Key Control Point |
|---|---|---|
| Head style | Oval head, low-profile domed contour | Head appearance and bearing surface |
| Shank hole | Straight hole, extruded or drilled | Hole depth consistency; clinch formation |
| Concentricity | Outside edge of head concentric with shank | Feed and die alignment in automatic machines |
| Units | Millimeters, before coating | Finished dimensions after coating by agreement |
| Length tolerance | Per Table 2 length increments and tolerances | Total length calculation for stacked joints |
Because semi-tubular rivets are used in automatic assembly machines, concentricity of the outside edge of the head to the rivet shank is an important functional attribute. On a low oval head rivet the axis of the head is difficult to locate, so the true head position method of measuring concentricity is not used; instead, practical gaging methods control the attribute.
3. Engineering Practice Essentials 🛠️
- 🔍 Hole depth and shank length matching: total clinch thickness = sum of workpiece thicknesses + clinch allowance; select the length increment per Table 2 so the set end forms a full clinch without damaging part surfaces.
- 🔧 Automatic assembly design: alignment of the feed chute, guide bushing, and forming die governs whether concentricity requirements are met; sample with concentricity gages during machine acceptance.
- 📋 Surface treatment: zinc or nickel plating for appearance parts must be defined in the dimension agreement, since coating build-up can change shank and hole fit.
- 📊 Quality inspection: perform dimensional sampling per the B18 quality assurance system, checking head appearance, clinch completeness, and absence of shank cracks; avoid excessive set pressure on brittle materials.
4. Frequently Asked Questions ❓
❓ Q: What is the difference between semi-tubular, solid, and blind (pop) rivets?
A: Semi-tubular rivets have a straight hole at the shank end, need low setting force, and suit high-speed automatic riveting. Solid rivets are stronger but need high setting force. Blind rivets are installed from one side for closed structures. Choose by strength, accessibility, and cost.
A: Semi-tubular rivets have a straight hole at the shank end, need low setting force, and suit high-speed automatic riveting. Solid rivets are stronger but need high setting force. Blind rivets are installed from one side for closed structures. Choose by strength, accessibility, and cost.
❓ Q: Why does this edition only cover the oval head?
A: This Standard began as the metric companion to ANSI B18.7, covering the most widely used oval head semi-tubular rivet first. The Committee intends to expand coverage to other head styles, tapered holes, full tubular rivets, and rivet caps as metric usage develops; other styles are available from manufacturers and should be based on the dimensions in this Standard.
A: This Standard began as the metric companion to ANSI B18.7, covering the most widely used oval head semi-tubular rivet first. The Committee intends to expand coverage to other head styles, tapered holes, full tubular rivets, and rivet caps as metric usage develops; other styles are available from manufacturers and should be based on the dimensions in this Standard.
❓ Q: Why is concentricity so critical for semi-tubular rivets?
A: Automatic riveting machines locate the rivet through feed tubes and guide bushings into the forming die. Head eccentricity causes jammed feeds, off-center setting, or incomplete clinch. Controlling concentricity is essential for production line stability.
A: Automatic riveting machines locate the rivet through feed tubes and guide bushings into the forming die. Head eccentricity causes jammed feeds, off-center setting, or incomplete clinch. Controlling concentricity is essential for production line stability.
🔍 Q: What does “dimensions apply before any coating” mean?
A: Table dimensions are nominal values before any coating. When plating or coating is specified, the finished product dimensions are as agreed between supplier and purchaser, avoiding coating build-up that causes shank interference or head protrusion.
A: Table dimensions are nominal values before any coating. When plating or coating is specified, the finished product dimensions are as agreed between supplier and purchaser, avoiding coating build-up that causes shank interference or head protrusion.
