Sheet-metal hardware: clinch parts and rivets

A laser-cut plate with one or two bends and a few pressed-in nuts or studs is a stiff, cheap mounting plate. Rivet two of them together and you get a box that one part cannot fold into. This page covers the bought parts for that pattern: which self-clinching (PEM-type) parts and blind rivets the checks know, what they cost and where to buy them. The checks come first and the price second, so a part is only ever ranked once it fits.

Drawn by tools/process_figures.py from cadagent.mechanical.sheet_hardware on research/sheet-hardware.yaml. A test redraws it and fails if the committed chart differs. The prices are as read on the dates in the footer.

The pattern, step by step

flowchart TD
    B["bends<br/>check_bends"] --> H["holes near bends<br/>feature_to_bend"]
    H --> C["clinch parts<br/>choose_clinch"]
    C --> P["place each<br/>check_placement"]
    P --> R["rivet seams<br/>choose_rivet"]
    R --> J["each seam<br/>check_joint"]
    J --> S["price<br/>cost"]
    classDef here fill:#fffdf5,stroke:#173d3c,color:#173d3c
    classDef out fill:#ffe1cc,stroke:#bd3a12,color:#173d3c
    class B,H,C,P,R,J here
    class S out

flowchart TD
    B["bends<br/>check_bends"] --> H["holes near bends<br/>feature_to_bend"]
    H --> C["clinch parts<br/>choose_clinch"]
    C --> P["place each<br/>check_placement"]
    P --> R["rivet seams<br/>choose_rivet"]
    R --> J["each seam<br/>check_joint"]
    J --> S["price<br/>cost"]
    classDef here fill:#fffdf5,stroke:#173d3c,color:#173d3c
    classDef out fill:#ffe1cc,stroke:#bd3a12,color:#173d3c
    class B,H,C,P,R,J here
    class S out

Each box is a function, and each one gives the next a number it needs: the bend allowance for the clinch part's distance to the bend, and the stack for the rivet's grip. The sheet-metal-hardware skill walks an agent through it.

from cadagent.manufacturing import sheet_metal as sm
from cadagent.mechanical import clinch, rivets, sheet_hardware as sh
sm.check_bends("5052", 1.6, [20, 20], relief_width_mm=1.6, hardware=True,   # flanges, relief, and the
               shop="sendcutsend")                    # shop's limits for a part with hardware
sh.choose_clinch("632", "5052-h32", 1.6)       # S-632-1 ($0.0847), then CLS-632-1 (no price read)
clinch.check_placement("S-632-1", "5052-h32", 1.6, edge_mm=6.5, to_bend_mm=8.0,
                       bend_allowance_mm=sm.bend("5052", 1.6)["allowance_mm"])
sh.choose_rivet(3.2, 3.0)                      # 1/8 in rivets for a 3.0 mm stack, cheapest first
rivets.check_joint("mcmaster-97447A015", [("5052-h32", 1.5), ("5052-h32", 1.5)], edge_mm=6.4, pitch_mm=25)
sh.cost({"S-632-1": 8, "mcmaster-97447A015": 24})   # $1.71 in pieces, $11.46 in packs; $6.16 to press the nuts in

The common, cheap choice

From research/sheet-hardware.yaml. Loose prices are Bossard Americas' prices for 1–249 pieces ([ref:bossard-pem-prices], read 2026-11-02). Rivet prices are McMaster-Carr's pack prices divided by the pack quantity ([ref:mcmaster-blind-rivets], read 2026-11-01). The pressed-in prices come from SendCutSend's ordering feed ([ref:sendcutsend-catalog]), which does not say whether its price includes the part.

So pressing a part in costs 7 to 11 times the loose part for the nuts and studs up to #10 and M5, and 3.6 to 5.8 times for the larger parts and the standoffs. A riveted seam costs a few cents per rivet. Stainless parts cost 1.8 to 3.3 times the steel ones, and none of the listed parts goes into stainless sheet.

Where to buy

flowchart TD
    P["PEM parts<br/>Bossard"] --> X["you press<br/>them in"]
    S["SendCutSend<br/>sheet, pressed"] --> Y["you rivet<br/>the seams"]
    X --> Y
    R["rivets<br/>McMaster"] --> Y
    classDef here fill:#fffdf5,stroke:#173d3c,color:#173d3c
    classDef out fill:#ffe1cc,stroke:#bd3a12,color:#173d3c
    class P,S,R here
    class X,Y out

flowchart TD
    P["PEM parts<br/>Bossard"] --> X["you press<br/>them in"]
    S["SendCutSend<br/>sheet, pressed"] --> Y["you rivet<br/>the seams"]
    X --> Y
    R["rivets<br/>McMaster"] --> Y
    classDef here fill:#fffdf5,stroke:#173d3c,color:#173d3c
    classDef out fill:#ffe1cc,stroke:#bd3a12,color:#173d3c
    class P,S,R here
    class X,Y out

Where each part comes from. A sheet part the shop has pressed its clinch parts into needs only riveting; loose clinch parts from a distributor are pressed in first. Rivets come from a distributor.

• PEM parts: Bossard Americas sells them loose without an account, with stock counts on each part page. PEM sells through distributors, so other sellers have them too.
• Rivets: McMaster-Carr sells them in packs of 100 or 250. POP rivets, whose ratings the rivet check also uses, are sold through distributors. No POP prices are recorded yet.
• Pressed in: SendCutSend presses in 151 hardware parts from its feed, when you order the sheet part with hardware. Check its own limits with the shop="sendcutsend" checks.

Keeping it current

Limits. These are dated public prices before shipping and tax. Minimum orders and tooling (a press or a rivet gun) are not counted. They are not quotes. A part the checks list without a price comes last, with offer empty. The strengths behind the checks are the makers' test averages, not allowables, so test a sample part.