Q. What are the pros and cons of clipped-head versus full-head nails? Are there any framing nailers that drive both kinds?
A. Eric Borden, owner of ESB Contracting in Forked River, N.J., responds: Clipped-head nails are collated at a steeper angle than round-head nails. The steeper collation angle provides two main advantages: There are more nails in a stick, and the working clearance (the angle between the gun and the work) is greatly improved.
The model building codes do not require the use of round-head nails. The codes specify nails by length and by shank diameter, not by the type of nail head. Lateral load capacity depends on a nail shaft’s shear strength, and withdrawal resistance depends on shank type. An increase in withdrawal resistance can be achieved by using a screw-shank or ring-shank nail.
The industry reference for evaluating pneumatic nails is the National Evaluation Report (NER-272), which is posted at the SENCO Web site (www.senco.com/pdf/facts/ner272.pdf). This report lists the nailing schedules for pneumatic fasteners for all of the model building codes (BOCA, CABO, SBCCI, and ICBO). [Editor's note: NER-272 has been replaced by ICC ESR-1539; you can find it posted here.]
A panel’s shear strength depends more on the depth to which fasteners are driven than on the shape of the nail head. Nail heads should be set flush with the surface of the sheathing, not countersunk. When fasteners are driven through the outer ply of plywood or OSB, shear strength decreases significantly. But if the nails are properly driven, there is no difference in performance between the two types of nail heads, because the pull-through values of both nails exceed the performance requirements for the assembly. Of course, regardless of the type used, proper spacing of the nails is essential.
Although there is no evidence that round-head nails provide greater shear strength or withdrawal resistance than clipped-head nails, some building inspectors ignore the facts and require round-head nails on exterior sheathing. These inspectors reason that the larger head area of round-head nails reduces the likelihood of overdrive.
Currently, all manufacturers make separate nailers for the two types of nail heads, and the nails are not interchangeable. Nails with a third type of head, the offset round head, are available from Paslode, Senco, and Hitachi. These nails can be used in clipped-head guns. For more information, see "Choosing Collated Nails," 6/00.