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Bolt-On Brass Neck Insert Installation

TRUSSRODSNeckInsertsTNI2at500The neck block and/or heel thickness on your instrument will determine the distance the bolt will thread into the insert. The neck should be close to having the right set on the body before marking and drilling for the inserts to avoid shifting the alignment when changing the neck angle. If the bolts supplied are too long, they can be cut down.

Marking for Inserts

  • First mark the center of the holes in the tenon or on the heel in the case of a flush mount neck. If the holes already exist in the neck block, then place the neck on the body and use a brad point drill bit or an awl to go through the holes and mark the tenon/heel. If you are putting the holes in the tenon/heel first, you will have to measure and drill out the neck block later. To prevent splitting, clamp a block of wood on either side of the tenon. Leave these clamped to the tenon through the installation process.

  • Once you have the centers of the holes marked, drill for the inserts. Use a brad point bit to drill out the holes. The TNI2 works best with a 10mm brad point bit (our part #HSS10B) and the TNIU and TNIU2 work best with a letter “G”( or .261") or a 17/64" bit. These are slightly larger than the bits the insert manufacturer recommends, but a slightly larger bit will prevent your heel from splitting when you drive the insert in. Make sure to keep the drill straight and parallel to the sides of the tenon/heel. This will make it much easier to drive the insert in and thread the bolt in straight. Drill the insert hole the depth of the insert plus 1/16”. Make sure you will not be drilling through the back of your heel before you commit to drilling.

    As an extra measure of quality and safety, reinforce the walls and bottom of the hole with thin super glue (our part# FGHO) applied with a pipette or a Q-tip. This helps strengthen the wood fibers and seal the grain to prevent moisture exchange in the endgrain.

Installing the Inserts

  • First thread the hex nut and then thread one of the inserts onto the same bolt until the bolt reaches the bottom of the insert. Bring the hex nut down against the insert and tighten them together with a wrench. Using the long end of the Allen wrench, place the end of the insert against the hole in the neck. Start to turn and apply pressure. Once you feel the thread catch in the wood, turn the wrench another half a turn and check for straightness. It is critical that the insert is straight, so check carefully. By moving the wrench one way or the other the insert can be straightened out to a degree. Once it is straight, continue turning slowly allowing the threads to cut into the end grain. Stop turning when the insert is just below flush with the face.

  • Turn the hex nut so that it is going back up toward the head of the Allen bolt until it spins freely. Back the bolt out and remove the hex nut. To really ensure that the insert willstay, wick a bit of thin super glue around the insert.

  • Repeat these steps for the second insert if applicable and then remove blocks clamped to the tenon.

Alternative Installation
An alternative to the installation technique above, is to oversize the insert holes and glue the insert in. This prevents problems created when the insert is not straight in the neck.