ASTM F680: nail testing and the MIBANT bend test

What ASTM F680 covers

ASTM F680 is a set of standard test methods for nails. In the pallet industry it matters because it defines the impact-bend test run on the MIBANT, the Morgan Impact Bend Angle Nail Tester. MIBANT is sometimes mistakenly expanded as "Morgan Fastener Test Apparatus"; the correct name refers to the impact bend angle.

In the test, a nail is clamped and struck with a controlled impact. The angle it bends to is the MIBANT angle, in degrees. A stiffer, stronger nail bends less, so a lower number is better.

Why nail stiffness matters in a pallet

Pallet joints fail mainly by nails bending and working loose as the pallet is handled, dropped and racked. A stiff nail resists that. Virginia Tech's Center for Packaging and Unit Load Design tested GMA-style pallets and found that pallets built with 11.5 gauge (0.112 in) nails lasted about twice as many trips as pallets built with collated 12.5 gauge (0.099 in) nails, 85.6% more durable in their result. Nail quality is one of the cheapest ways to add service life.

Key numbers

MIBANT quality bands (industry guidance)

These bands are published in trade press rather than in the standard itself. The Uniform Standard also limits shank failures in the test to no more than 8% of fasteners.

From MIBANT to bending yield strength

The Uniform Standard for Wood Pallets (Annex F) gives a public conversion from MIBANT angle to nail bending yield moment, and from that to bending yield strength using the shank diameter. Its minimum bending yield strength is 100 ksi (690 MPa). Bending yield itself is the subject of a related standard, ASTM F1575, and nail dimensions are covered by ASTM F1667.

Example acceptable nails (Uniform Standard Annex G)

These are the example minimums for reusable pallets. Quality nails on real spec sheets often test at 21 to 36 degrees.

Other checks that go with MIBANT

MIBANT measures stiffness. Two other properties decide how well a nail holds:

• Thread press-out is the thread crest diameter minus the wire diameter. Trade guidance rates more than 0.020 in excellent, 0.016 to 0.020 in good, 0.012 to 0.015 in marginal and under 0.010 in poor.
• Fastener withdrawal characteristic (FWC, or Cw) summarizes thread geometry. Plain shank nails are 1.00; threaded pallet nails on real spec sheets run about 2.58 to 3.69. The Uniform Standard minimum is 1.9 for reusable pallets and 1.5 for single-use.

Delivery format matters too. Collated nails for automatic nailers are often thinner (12.5 gauge) than bulk nails (11.5 gauge), and that trade-off shows up in pallet life, as the Virginia Tech result above shows.

Who uses ASTM F680

• Fastener makers certifying their nails.
• Pallet mills verifying incoming nails and reporting the MIBANT angle on spec sheets.
• Buyers writing nail verification into RFQs. ANSI MH1 includes a nail quality protocol that relies on these tests.
• PDS, which takes the MIBANT angle (or bending yield strength) as an input to its connection and durability analysis.

What to ask a nail supplier

• The MIBANT angle for each nail you buy, with the test method.
• Wire diameter, thread crest diameter, thread length and head diameter.
• The calculated FWC.
• Whether the nails are collated or bulk, and the gauge in each format.
• How often they test, and what share of nails may fail the bend test.

How it shows up on a spec or drawing

A PDS-style fastener block lists the fastener ID, type, length, wire diameter, thread dimensions, head diameter, MIBANT angle, the fastener withdrawal characteristic (FWC) and the total count. For example: 2-1/4 in helically threaded, 0.112 in wire, MIBANT 36, FWC 2.58, 84 per pallet. An RFQ can require MIBANT certificates or a fastener spec sheet from the supplier.

How palletdesign.ai uses it

palletdesign.ai records the fastener type, length and per-joint count, and computes the total nail count from the parts list using Uniform Standard Table 5 minimums. It does not test nails or model MIBANT, so specify nail quality separately on the RFQ. The nail quality page and pallet nails cover what to ask for.