Restoring a Divider: Part 2

Tapping a New Thread

When you can’t find the right thumb screw for an old tool (see Part 1 here), your best option is to drill and tap a new hole to accommodate a modern fastener. In the case of our antique divider, I found an old thumb screw from a lampshade retaining ring that was a perfect fit. Rather than enlarging the original hole—which can sometimes compromise the integrity of the piece—I opted to drill and tap a fresh hole on the opposite side of the mortise wall.

The Tapping Process

Tapping a new thread is a straightforward process, but it requires care and patience. The key steps are:

• Drill the correct-sized hole – This ensures the tap has the right amount of material to cut into.
• Use a tap to cut internal threads – This allows the new screw to seat properly.
• Lubricate with oil – Reduces friction and prevents the tap from binding or breaking.

Today, you can buy inexpensive drill-and-tap combo sets, which feature bits with hex shanks that transition from a drill to a tap, allowing you to complete both steps in one go. While these are convenient, I recommend a more controlled approach:

• First, drill the hole using a drill press or handheld drill.
• Then, remove the drill/tap bit from the chuck and install it in a T-handle 1/4″ hex bit holder.
• This method provides better control and reduces the risk of breaking the tap, which can be difficult to remove if it snaps inside the hole.

Step-by-Step Guide

1. Mark the location – Use a center punch to create an indentation, guiding the drill bit.

2. Drill the hole – Install the drill/tap bit in a drill chuck, apply a drop of oil, and drill slowly.

3. Tap the threads – Remove the bit from the drill and install it in a T-handle 1/4″ hex bit holder. Slowly turn the tap into the hole, applying steady pressure.

4. Back out to clear shavings – If tapping becomes difficult, reverse the tap slightly to break and clear metal shavings, then continue forward. Reapply oil as needed.

Conclusion

With the new threads cut, the antique divider is back in working order. This process not only restored the tool but also extended its useful life for years to come. The ability to repair missing hardware makes buying used tools far less intimidating, knowing that minor issues can often be fixed with simple techniques. So next time you come across a well-worn tool with a missing screw, don’t pass it up—you might just bring it back to life with a little drilling, tapping, and patience.