3/16 inch since you are using a screw and you want the threads to catch the wood
if you meant lag bolt, make it 5/16 inch so the bolt will slide through
The recommended drill bit size for a 1/4 lag screw is 3/16 inches.
I use 1/4 drill bit for a 5/16 lag screw in most materials.
quarter inch drill bit
For a 1/2 inch lag bolt, you should use a drill bit that is slightly smaller in diameter, typically a 7/16 inch drill bit. This allows for a snug fit and proper anchoring of the bolt.
For installing heavy-duty shelves in your garage, you should use a 3/8 inch lag bolt drill bit.
A 3/16 drill bit.
The best screws to use for mounting a TV to studs are lag screws or lag bolts. These screws are strong and durable, providing secure support for the TV on the wall. Make sure to choose the appropriate size and length of lag screws based on the weight and size of your TV.
You should use a bit that is just a little bit smaller, but only drill the depth about 2/3 of the distance. This will allow solid penetration into the undrilled wood. 5/16 lags = 3/16 or 1/4 pilot drill bit.
Lag bolts are typically larger and have a hexagonal head, while lag screws are smaller and have a flat or round head. Lag bolts are more suitable for heavy-duty construction projects due to their larger size and stronger hold.
It depends on the material you are fitting it into. In most wood I pre-drill a 1/4 hole for this. In softer woods i would drill a smaller hole .
To securely install lag bolt anchors in concrete walls, follow these best practices: Drill a hole in the concrete wall using a hammer drill and a masonry bit that matches the size of the lag bolt. Clean out the hole to remove any debris. Insert the lag bolt anchor into the hole and tighten it with a wrench until it is securely in place. Use a torque wrench to ensure the lag bolt is tightened to the manufacturer's specifications. Allow the anchor to set and cure according to the manufacturer's instructions before applying any load.
For a 1/4 lag screw, it is recommended to drill a pilot hole that is slightly smaller in diameter than the screw itself and at a depth that is equal to the length of the screw.