How to Use a Trim Nailer Gun

Learn to use a trim nailer

The first time I used a pneumatic trim gun, I was hooked. It's not just that it was lightning fast. I loved being able to install hardwood moldings without predrilling to prevent splitting, and I was happy to leave my nail set mostly in my toolbox. But even better was the fact that nail guns allow you to hold a molding in exactly the right spot with one hand while you instantly nail it in place with the other. And small nail guns called brad nailers allow you to quickly and easily secure thin, fragile moldings without ruining them. That's a job that otherwise requires the dexterity of a surgeon.

But things can go wrong. In this article, we'll show you the most common problems you'll encounter when nailing trim with a nail gun and the techniques you can use to prevent them.

Avoid blowouts by watching the angle

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Photo 1: Problem: Nail blowout

If you're not careful the nail will come out where you don't want it.

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PHOTO 2: Solution: Angle the gun in

Angle the gun toward the unseen side.

Once you master this angle technique, you'll have no trouble shooting nails exactly where you want them. Start by positioning the center of the nail gun tip exactly where you want the nail to enter the wood. Then carefully align the nail gun with the path you want the nail to take, just like when you line up a pool cue before striking the ball. Photo 1 shows what can happen if you get careless and angle the gun wrong. When you're nailing into door jambs or other areas where only one side shows, point the nail gun slightly to the hidden side where it won't show if the nail pops through (Photo 2).

Occasionally nails hit a knot or follow the grain—and pop out despite your best effort. If this happens, break or cut off the protruding nail with a nipper and use your nail set to recess the remainder.

Avoid split ends by placing nails accurately

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Photo 3: Problem: Split trim at the ends

Be careful. If you nail too close to the end of the trim, it'll split.

Driving nails with these tools is so simple that it's easy to get carried away and put nails where they don't belong. (Ask any painter who has to putty all the extra holes!) With practice, you'll get a feel for where the nail comes out of the gun and be able to drive a nail precisely. Photo 3 shows the result of placing a nail too close to the end of a molding. The same thing will happen if you nail too close to the end of a baseboard, especially on short pieces. Make sure to keep nails a few inches from the end of moldings to avoid splitting the wood. Brad nailers, which drive thinner and shorter nails, are the exception. With these, you can usually nail within 1/2 in. of ends and 1/8 in. of edges without splitting the wood.

Use the right size nail

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Photo 4: Problem: Exposed nail

If the nail is too large it can come out where you don't want it.

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Photo 5: Solution: Use a smaller nail

Brad nailers are better for work that's close to edges

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Different nail sizes

Be sure to get the right size nails for the job.

Changing nail sizes in the middle of a job is bothersome. It's tempting to use the nails that are loaded and hope for the best. But it's a bad idea.(Photo 4). We should have used a 3/4-in. brad or at most a 1-in. 16-gauge nail on this miter. A good rule of thumb is to pick a nail long enough to go through the material you're fastening and penetrate the underlying wood about 3/4 in. to 1 in. Allow more penetration for heavy-duty jobs like nailing door jambs, and less for fine work like securing miters.

I own a 15-gauge nailer and a brad nailer and keep them both connected to separate hoses while I work. (Install a T-fitting at the compressor to connect two hoses at once.) With this setup, it's an easy matter to pick up the brad nailer for intricate jobs like pinning.

Avoid underdriven nails

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Photo 6: Problem: Nail won't set flush

Nails that don't set must be driven in or removed. Use side-cutting pliers to pull protruding nails. Or use a nailset and hammer to drive them in.

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Photo 7: Solution: Increase the air pressure

Increase the air pressure on your compressor, or use a smaller nail if the nails aren't being driven in completely.

Nails that don't set, or that are left sticking out (Photo 6), are usually the result of pressure that's too low, a nail that's too long or an improperly adjusted nail gun. If the nail is sticking way out like the one in Photo 6 try increasing the air pressure to the maximum allowable for your nail gun (90 to 100 lbs., or check your instructions). If the nail still won't set, try loading shorter nails or brads.

The nosepiece on some nail guns is adjustable to help control how deep the nail is set. Use this in conjunction with pressure adjustments (Photo 7) to fine-tune your nail gun until the head of the nail or brad is slightly recessed. Keep a nail set handy for the occasional protruding nailhead.

Don't bother pounding in nails that protrude more than 1/4 in. They'll just bend over and dent the trim. Instead, grab the shank and bend it back and forth until it snaps, or use a side cutting pliers (Photo 6) to cut the nail near the surface. Then recess the rest with a nail set.