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Tips on using threaded inserts

Shop fixtures and jigs often require the installation of various clamping or adjustment knobs. That's when you'll reach for threaded inserts. Commonly available in sizes from #8-32 (a #8 screw body with 32 threads per inch) to 3/8"-16 (a 3/8" screw body with 16 threads per inch), there are two basic types: thread-in and press-in, shown top right..

Use thread-in inserts in softer woods and plywood where their coarse outside threads cut easily into the surrounding wood. Simply drill a hole sized for the body of the insert, and screw it into place. In very hard woods, such as white oak and maple, or when the insert is close to the edge of a part and screwing it in may split the wood, drill a hole slightly larger than the outside thread diameter, and epoxy the insert in place. To protect the internal threads from epoxy, cover the end of the insert, as shown bottom right.

Press-in inserts, with their barbed exteriors, work well in hard woods, soft woods, and plywood. Drill a hole sized for the body of the insert, and press it into place with a clamp or tap it in with a hammer and a block of wood. For applications in which the clamping action tends to push the insert out of the wood, such as the knobs that tighten down on the drill-press fence extension rods, drill a hole that engages just the tips of the insert barbs and epoxy it in place.


Comments (6)
barnagh wrote:

I often use these to attach necks to electric guitars. I use a length of threaded mild steel rod in my drill press, with two lock nuts, to wind them carefully into place, in hardwoods. The diameter of the pilot hole is critical, measure at the base of the threads with a caliper and add a little bit for clearance. Use a run of candle wax for lubrication. they are immensely strong when they are well installed.

11/25/2015 10:08:40 AM Report Abuse
tomnlisaw wrote:

I used the thread insert in maple. I used a tap the size of the outside threads on the insert and threaded the maple.

12/13/2012 03:20:55 PM Report Abuse
jlcusimano1 wrote:

Most important part of installing inserts is the hole diameter. How does one go about determining this diameter to be big enough to drive w/o damage (brass inserts break easily)and small enough to hold securely??

12/13/2012 02:15:44 PM Report Abuse
cgoog-sale1 wrote:

use a dowel the same diameter or slightly less wraped in a layer of saran or plastic wrap. That will keep the expoxy from sticking to the dowel. Also it will help to wax a bolt to fit the insert to keep expoxy out of the insert. This will also help to keep the insert at the right "depth" in the hole.

4/19/2012 10:25:03 PM Report Abuse
Chips N Dust wrote:

I see that your pressed in inserts that are held with epoxy are only drilled to a depth of the insert. If you have to account for a bolt that will be longer that just the insert, how do you expoxy the insert in that situation? For example a leg leverler would need a hole deeper than the insert is long by say at least 3/4" to 1 1/2"

3/28/2012 05:33:42 PM Report Abuse

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