I use 1/4 drill bit for a 5/16 lag screw in most materials.
That size is 8-32. The drill bit for a clearance hole is 11/64, or a #17 drill bit.
If they are self tapping screws, the drill bit is as thick as the solid barrel of the screw. If you want the screw to go through easily to have a nut on the other side, then the drill bit is slightly larger than thread size.
I use a 3/16 drill bit for that.
I drill a pilot hole the size of the 'barrel' of the screw. -I always use a combination drill bit for sinking screwheads. The first part of the bit is the diameter of the 'barrel' of the screw and the step, one inch higher is the size of that screw's head. (The barrel is the diameter inside threads) -I have a set of these drill bits for #6, #8, and #10 screws and they are great.
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.
Drill bits and screws are not the same and cannot be converted. vido produces drill bits with high quality, exported overseas and loved by the public. If you want to buy a drill, you can go to VIDO's official website to check.
It's one that has a point of a basic screw size, and a bit further up it widens to the size of that screws head, so you can make a countersink hole with the same drill.
That's a pretty big drill bit, -it drills a hole just a tad larger than 3 3/8 inch wide.
A 3/16 drill bit.
Use appropriate sized drill bit to drill completely through the stuck screw and retap the hole if new screw is necessary.
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