How Tubs Are Drilled
Some tubs are purchased pre-drilled, and others drilled at the time of order. To have a custom drilling done, it's necessary to provide the faucet's specification sheet which details the hole diameters, the spread of the faucet, and diameter of the faucet escutcheons.
With custom drillings, special templates are placed over the tub to mark the locations of the faucet holes and ensure a perfect setting. Then a low-speed drill (600 RPM), fitted with a diamond encrusted hole saw, is used to cut the holes. Light pressure is applied to the bit, creating a smooth hole without distorting the tub walls.
Faucet holes drilled in tub wall are 1-1/4" in diameter. Holes drilled in the tub rim are 1". Typically, the overflow hole is 1-1/4".
There are three distinct tub drilling options, depending on the type of tub and the faucet you'll be using: tub-wall-mount drillings, deck-mount drillings and overflow-only drillings.
Not to be confused with a faucet installed into the bathroom wall, tub wall-mount faucets are installed on the interior wall of the tub. With a traditional single-ended roll-top tub, the tub has one "finished" end and the other end designed for placement against a wall to access water lines. For this tub type, you'll want to use a tub wall-mount faucet. Many tubs of this sort are manufactured with the holes drilled in the actual wall of the tub. The faucet holes are 3-3/8" apart when measured from the centers of each hole. The overflow hole is usually centered 3" below the faucet holes.
For tubs that have two finished ends, the standard application is a deck-mount faucet. Also called rim-mount faucets, these fixtures require drillings on top of the tub rim, the holes 7" apart when measured from their centers. The overflow hole is drilled in the tub, centered between the two faucet holes.
Freestanding Tub Faucets
With a slipper or other freestanding tubs, the faucet may not physically mount to the tub. Therefore, only an overflow hole needs to be drilled into the wall of the tub. The tub may also be pushed up against the wall of the home and a wall-mount faucet can be used. As mentioned above, the wall-mount faucet is connected to a water supply located in the wall of the home, unlike the freestanding faucet, which conencts to water lines through the floor.
DIY Tub Drilling
For people who prefer to drill the holes themselves, we recommend using a wood hole saw drill bit, found in many hardware stores. When using the hole saw, it's important to not let the bit too hot. Typically, a wood hole saw will last for only one or two sets of tub holes.