Lag Screw Pilot Hole Sizes for Wood
Drilling Lag Screw Pilot Holes
Pilot Hole Size for Softwood | Lag Screw Diameter | Pilot Hole Size for Hardwood |
3/32″ | 1/4″ | 3/16″ |
9/64″ | 5/16″ | 7/32″ |
11/64″ | 3/8″ | 1/4″ |
1/4″ | 1/2″ | 11/32″ |
5/16″ | 5/8″ | 1/2″ |
3/8″ | 3/4″ | 9/16″ |
Lag Screws in Softwoods
When drilling into softwoods, it’s always worth trying a smaller sized bit. The lower density wood fibers allow for greater compression when receiving the screw. This results in an overall tighter fit and more secure fastener. There are a few exceptions to this like aromatic cedar and other hard softwoods. If you aren’t sure how if you should test a smaller drill bit, we have a chart with all the hardness ratings for North American softwoods. Though there’s no need to countersink your lag screw, we recommend smoothing the surface.
Lag Screws in Hardwoods
The most challenging part with hardwoods is driving in the actual lag screw. If you have a pack of nut setter bits, you’re in good shape…at least for the smaller sizes. For the other users out there that will be using a socket on a 1/4″ hex shank, it’s a different story. As the lag screw enters deeper into the pilot hole, the socket will likely ground out before the screw is fully inside. When you encounter this, stuff some small washers into the back of the socket. This will effectively make the socket shallower when it wraps around the lag screw’s head. Do be mindful that it is of course safer and quicker to use nut setter bits.

If your socket wrench bottoms out, insert some smaller washers between the top of the lag screw & the bottom of the socket. This will result in an effectively shallower socket.
Recommended Tools for Drilling Lag Screw Pilot Holes:
DEWALT Titanium Pilot Point Drill Bit Set
Why we like it:
- Drill bits feature tapered tips for greater strength
- Titanium coating provides greater longevity
- Complete coverage for all wood screw sizes
- Works for wood, plastic, & metal
- Shanks have flattened side to prevent slipping
DEWALT Cordless Power Drill
Why we like it:
- Handles well with no latency in power
- Compact size fits into tight spaces
- Impressive battery life with backup included
- LED light illuminates dark areas when drilling
- When it comes to power drills, stick to quality brands
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