Drilled Holes With Threads: How To Determine What Fits These Holes

How many times have you encountered a drilled hole in metal or wood and these holes have threads, like screws? It is actually pretty common, especially when these holes are drilled to accommodate bolts and/or screws of accompanying size. Yet, when you have the drilled hole but you do not have the bolt or screw, how can you find out what fits the hole? If it is a wood hole, how do you make something to fit it? The answers to these questions follow. 

Use a Nut Thread Gauge

A nut thread gauge is used to find the size, expanse, and type of thread inside a hex nut or other screw-on nut. It goes inside the hole of the nut and measures the threads from inside. In this case, where you are attempting to measure the threads inside the wooden or metal pre-drilled hole. You will have to use both metric and standard/empirical gauges to find an approximate fit for the drilled hole when you do not know what size drill bit made the hole to begin with. 

A Threaded Wood Hole

Many handcrafted toys and wooden furniture pieces use threaded wood holes for stronger assembly. The holes are drilled, which makes it easier to discover just what size drill bit made the holes. Using a nut thread gauge will help you find the size of the threads and the size of the drill bit that was used. Once you figure out what the proper size of the threads and the gauge of the drill bit were, you can begin to work on a replacement wooden bolt. It requires an extra set of tools to craft the wooden bolts, but you may enjoy the process and the knowledge of knowing that the wooden bolts can be glued in with wood glue as they are screwed into place. Otherwise, it is okay to use the proper size/gauge of bolt or screw to insert and twist in the wooden holes. 

Metal Holes May Need a Little Grinding

The thing with drilling metal is that it can leave small metal shavings and rough edges behind on the threads inside the holes. It is possible to flush the holes and clean them up with some metal wire brush tools, but you have to be very careful not to grind too much. If you grind too much, the nut thread gauge used to determine the size of the hole's threads will not be accurate. Remember that if you are the one cleaning it but not the one who drilled it.