T-nuts are threaded steel inserts with prongs that insert claws into wood when they are tightened, and often work when wood screws fail. After a T-nut is installed, a common bolt is used to join corresponding parts together. If you can drill a hole, you can install a T-nut.
Why Use T-Nuts
T-nuts and are more effective than wood screws. They are less likely to strip, or cause cracks or splits in any type of wood. Parts can be mass-produced with T-nuts, assembled and reassembled for shipping purposes, or packaged as a kit. T-nuts resist movement and vibration, and can be tightened at regular intervals. Because they have prongs, t-nuts grip softer materials, such as particle board, better than wood screws, which tend to strip.
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Purchase matching bolts when buying T-nuts. Bolt sizing information should be printed on the packaging.
Common T-Nut Applications
Common T-nut applications include speakers, chair seats or other upholstered furniture parts, among other things. Cabinetry, shelving or boxes -- things that you might want to disassemble later -- can benefit from T-nuts.
Speakers are a perfect example of a useful T-nut application. The constant vibration of speakers, particularly large bass speakers, weakens common wood screws. With regular tightening, T-nuts, have more longevity than wood screws for speaker installation.
Beds and Chairs
You'll often find T-nuts joining headboards to bed frames, or on removable braces or legs. T-nuts allow you to build the chair or headboard, finish it with stain and lacquer, add T-nuts to the upholstered seat or headboard of any type, and screw it on later.
Design, cut and layout cabinet jambs, sides, tops and bottoms. Mark and measure where the parts join together, but instead of screwing them together, build the cabinet or shelf system using T-nuts for ease of transportation , assembly and disassembly.
Wheels and Casters
T-nuts are often used to install casters. T-nuts are more effective than wood screws to control the stress of constant movement, and the caster can be tightened as needed. Another benefit of using T-nuts to install casters -- on some models you don't need bolts, the caster screws directly into the T-nut.
Install a T-Nut
Step 1: Size the Bit
Compare the drill bit to the end of the T-nut shank. The comparison is taken from the shank of the T-nut, which is the round cylinder. If you're not sure about the size, hold the end of a drill bit to the end of the T-nut shank. If it matches, it will work. The most common T-nut is 1/4 inch.
If you're unsure about bit size, err on a larger size bit. It's common to use a 5/16-inch bit for a 1/4-inch T-nut. The general rule of thumb is that the hole should be slightly larger than the shank, but no smaller than the shank. If you only have a 1/4-inch bit available, it's fine to use it.
Step 2: Drill the Hole
Drill the hole for the T-nut using a drill driver. Take extra care to ensure that the hole is perfectly perpendicular to the wood. Any tilt or angle of the bit can cause the T-nut to fail, because the bolt will also be angled.
Clamp two wood parts together tightly, as if they were already joined together. Drill a 1/4-inch hole through both of them at the same time to ensure that the parts and holes line up correctly. Remove the clamp and add the T-nut where you need it.
Step 3: Insert the T-nut
Fit the shank end of the T-nut into the hole. Push it down with your fingers, just enough so that the prongs dig into the wood slightly. Check to ensure that the T-nut is perpendicular to the wood.
Step 4: Seat the T-nut
Tap the T-nut with a hammer to drive the prongs into the wood. When the T-nut is flush with the wood, it's seated properly.
If the T-nut is tilted or has a gap under it, continue tapping until it's completely flush with the wood around the perimeter. If you can't get it flush, pry out the T-nut with a screwdriver and reinsert it. If you've drilled the hole crooked, use the bit and drill driver to straighten it out.
Step 5: Drill Another Hole
Drill a corresponding hole in a piece of wood or object that you wish to join to the T-nut. Insert a matching bolt through the hole. The bolt should extend a minimum of 1/2 inch from the corresponding hole. If it's too short, get a longer bolt.
Step 6: Thread and Tighten
Insert the end of the extended bolt into the T-nut. Use a wrench or drill driver to tighten the bolt into the T-nut, securing the two pieces of wood together.
Either Side of the Wood
T-nuts can be installed on either side of the wood. Speakers, for example, typically require that the T-nut be installed on the opposite side of the wood from the speaker flange. In this instance, or when there's not enough room to swing a hammer, use the bolt or a large wing nut to tighten bolt into the T-nut, pulling the prongs forcefully on the opposite side and sinking them into the wood.
T-nuts will leave a slight protrusion or relief where the round, T-nut flange flushes with the surface of the wood. If it's an issue for your particular application, install a sawtooth bit in a drill driver and countersink a slight -- about 1/6 inch deep -- depression or countersink hole so that the T-nut flange fits below the surface.
Specializing in hardwood furniture, trim carpentry, cabinets, home improvement and architectural millwork, Wade Shaddy has worked in homebuilding since 1972. Shaddy has also worked as a newspaper reporter and writer, and as a contributing writer for Bicycling Magazine. Shaddy began publishing in various magazines in 1992, and published a novel, “Dark Canyon,” in 2008.