So you have to fasten something to anything with a machine screw or a wood screw.... but what sized hole should you drill? We all have various tools to do every little thing but how many of us use a drill gauge? Drilling the correct sized hole can make all the difference between a professional installation and a regret.
A must have in my opinion is a 29 bit drill index and a matching drill gauge. The holes in the gauge correspond to the drill sizes in the index (except for maybe the larger holes in the index). I believe they both go up by 1/64th of an inch. This one is a cobalt drill set from Sears Craftsman and will run you about $120. You need cobalt to drill stainless. As I break drill bits I replace them with individually bought ones to keep my set complete. If you never intend on drilling stainless you can get a similar drill index for less than half of that.
The drill gauge is an old school heavy steel one my father had laying around. It doesn't show well in the photo, but the drill gauge has the fractional size of the hole stamped next to the hole. This is the size of the drill bit to use to make that hole. Do not by a plastic one as it will not hold up.
Lets say you have selected the appropriate machine screw to install an item. You then pass that screw through a hole that fits on the gauge to see what size drill to use. If you want a tighter hole you would use the first smallest size that fits. If you want it a little looser you would go a size up.
Let say you want to mount a wood screw. In this example the screw fits a 1/4 inch hole.
But a wood screw has to go into a smaller hole in order for the threads to hold. So you try a few holes smaller and pick the one where you cannot get the screw to thread into, in this case 13/64ths. In fact you can even go one size smaller at times and if the screw is hard going in you can then drill it again with the next size up drill bit.
In this example if you drilled a 1/4 inch hole you would be screwed as there would be nothing for the threads to hold to. However, sometimes this is what you want to happen. For example if you wanted to screw a piece of teak to something with a wood screw. You may not want the threads to grab the piece of teak, rather you want the screw to grab to the thing you are screwing the teak into. You would line the teak piece up to where its being mounted, drill a 13/64th hole through both items, then remove the teak and drill a 1/4 in hole in just the teak. When you install the screw it will pull the teak hard against the mounting surface for a great hold.
My set fits together nicely so I always have them together.
In this photo I am using a automatic center punch to create a dimple for the drill bit to start in. As you depress the punch, it is spring loaded and will hammer a dimple in anything including steel.
I then use a small drill bit to drill the first hole as a small drill bit will be less likely to try to walk out of the dimple. I then follow it up with the correct sized bit which is lying on the table.
This process takes the guesswork out of which drill bit to use for which screw and leaves you with professional results and peace of mind. My drill, bits, gauge and center punch all fit nicely in the tool bag that came with my drill. Drilling holes may seem simple but this method makes it foolproof to get it done correctly.
