Posted: Dec 14, 2011

Rockler Thread Detective

Extremely handy gizmo to have around

Available in both standard and metric from Amazon

Many times, when repairing items around the house, you need to replace a lost or stripped bolt or nut. But getting the right replacement may be a pain. For example, the bolt is gone and it goes into a part you can't carry to the hardware store. So you're left guessing at the size and thread pitch.

My dad was really good at that. He could look at a bolt and tell you "yeah, that's a 3/8 - 24" or "go pick up a metric M6". Me, not so much. (He was also way better at guessing wrench sizes, too)

So, for me, having something like the Rockler Thread Detective around is a real help. I can quickly ID the size and thread of bolts, studs, nuts, threaded holes, etc.

Rockler makes two versions of the Thread Detective. The standard version has 14 sizes, from #6-32 up to 1/2-13. The metric set has 11 sizes, M4-0.7 through M12-13. It's a nice touch that the standard set is black and the metric red.

Each size has a threaded stud for checking nuts or other threaded holes. On the other side is a threaded hole you can use on bolts or threaded studs.

Each version also has an attached plastic card with both standard and metric scales you can use to measure the length of the bolt/stud.

The sizes are held together with a braided steel cable, with a handy loop on each end you can use to hang the set on a handy nail in the wall.

I've found the Rockler Thread Detectives to be easy to use. My only complaint is that there's no way to detach the size checkers from the cable. This can make Thead Detective very clumsy if you're using it to check a threaded hole or stud, especially if it's in a tight space. Turning the size checker with all the other's attached can be difficult if not impossible, some way to remove them from the cable would be a nice addition. I've seen at least a half-dozen thread detectives of similar designs and they all share the same problem. One different version, however, is Lee Valley's Thread ID, which allows you to remove the threaded studs and use them separately in a threaded hole. However, the Thread ID has it's own issues, namely it would be difficult if not impossible to use on studs, plus you have to remove the stud from the block to check a bolt. Also, the Thread ID is limited to a maximum size of 1/4" or M6.

Overall, the Rockler Thread Detectives are sturdy, well-made, and a very worthwhile addition to the shop.