Brad nail lengths?

[tjr]

I'm planning some basement shelving made from 2x4's and plywood in my junk pile. Want to use my new brad nailer to nail the plywood shelves to the frames - is there a rule of thumb (other than "don't nail your thumb") for brad length to nail 1/2" or 3/4" plywood to dimension lumber?

Thanks for any help...

[Black wallnut]

I don't know if there is a right answer but I'd use the longest that would not go all the way through and that my gun could shoot to just below flush.

[LarryG]

Here are two rules of thumb that don't always agree with each other:

1. Fastener length = 3x the material being fastened; 1/3 of the fastener length is in the material and 2/3 is in the substrate. So for 1/2" material you'd use 1-1/2" nails.

2. Express the thickness of the material being fastened in eighths of an inch -- i.e., 1/2" material is 4/8" -- and the number of eighths is the penny size of the nail you should use. So for 1/2" aka 4/8" material you'd use a 4d nail, which happens to be 1-1/2" long and agrees with ROT #1 above. But for 3/4" aka 6/8" material, this ROT calls for a 6d nail which is only 2" long, rather than the 2-1/4" suggested by ROT #1.

Rules of thumb being what they are, either will be close enough in most cases.

[cabinetman]

Black wallnut nailed it pretty good. Brad length will be limited by the capacity of the gun. For 18 ga, many go to 2" and some to 2 1/8". The trick is what Mark said is to get it as long as possible without going through.

My first staple and brad guns were Duo Fast, and in 18 ga both brads and staples 1 1/4" were the maximum lengths they would shoot. I never had a problem with fastening 3/4" hardwood plywoods to any substrate with that length. Shortly after buying the guns they offered a magazine exchange to accept 1 1/2" staples. For gauges greater than 18, such as 16 ga, or 15 ga the fasteners can accept longer lengths.

For seating fasteners to a lesser depth, the air pressure can be reduced slightly. You'll find a happy medium of minimum pressures to actuate the gun efficiently.
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[LCHIEN]

i use teh 2/3 of the brad in the backing material rule that LarryG recommended provided that the backing is thick enough to hold the nail. From personal experience, you don't want a nail to come more than 1/8" from breaking out - because the wood will start breaking out even if the nail does not.

[shoottx]

Find the length that hits your thumb on the outside of the nailing surface and the go at least 1/4 in shorter.

[cabinetman]

i use teh 2/3 of the brad in the backing material rule that LarryG recommended provided that the backing is thick enough to hold the nail. From personal experience, you don't want a nail to come more than 1/8" from breaking out - because the wood will start breaking out even if the nail does not.

You're still limited to the capacity of the magazine. For example, if nailing two pieces together of defined thickness, like 1/2" to 1/2", the 2/3 rule doesn't apply. All you can do is figure out a good length, remembering that the head may seat 1/8" or more, depending on the material. On denser applications, a shorter length may be necessary for the head to seat. On some fastenings where glue is used, the fastener only has to hold sufficiently until the glue dries. Then there are situations where a brad is used just to maintain a position until a screw can be driven.

For an example like nailing 3/4" to the edge of a stud, you're back to the limits of the gun.
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[tjr]

Thanks, y'all. Sounds like 2" could work for everything unless I wind up nailing 1/2" plywood to the 2 side of a 2x4, where 1 1/2" would work, or in a pinch 1 1/4" which would also do for nailing 2 3/4" boards together.

[LarryG]

Thanks, y'all. Sounds like 2" could work for everything unless I wind up nailing 1/2" plywood to the 2 side of a 2x4, where 1 1/2" would work, or in a pinch 1 1/4" which would also do for nailing 2 3/4" boards together.

Sounds like a plan to me. In the case of the last, it would be a good idea to back up the mechanical fasteners with some glue. Failing that, use more nails than you might otherwise use, and if possible drive/shoot them from both sides. (This is really a different situation than you originally asked about, which was attaching 1/2" and 3/4" plywood to dimensional lumber.)

My 18ga nailer will shoot up to 1-1/4" brads, and I have used it to attach 1/2" material to the supporting framework. But for thicker materials, I find some other way. You don't ever want to let limitations of the tool you happen to have in your hand dictate the way you work. That's the quick road to shoddy workmanship.