Pilot hole for a 1/4" lag screw
Hardwood
3/16"
Softwood
3/32" to 1/8"
Published charts do not agree on lag screw pilots, so this page gives the range. Start at the smaller end and test on scrap.
1/4" lag screw pilot hole sizes
| Lag screw diameter | 1/4" 6.35 mm |
|---|---|
| Softwood, chart 1 | 3/32" |
| Softwood, chart 2 | 1/8" |
| Hardwood, chart 1 | 3/16" |
| Hardwood, chart 2 | 3/16" |
Which size to pick
The drill size depends on the wood and on the screw's thread depth. Dense wood and long screws need the larger end; soft wood the smaller.
If the screw is hard to drive or the head twists, drill a bit larger. If it spins freely, drill a bit smaller. The shank (unthreaded part) also needs its own full-diameter clearance hole in the board you are fastening.
Tools for this job
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