Drilling for lag bolts

[kevin nee]

I am putting casters on a bench.
I am using 1/4 inch by 1 1/2 lag bolts.
The material that the bolts will be in is 1 1/2 red oak.
What size pilot hole should I drill?
Is there a chart or a rule of thumb?
Thanks in advance,

[Kent A Bathurst]

Here's what I use....in fact, my copy has gotten pretty ratty [it sits on the drawer bottom, under 6 or 7 boxes of drills, baggies of drills, pouches of drills.............]

http://www.woodmagazine.com/woodworking-tips/techniques/free-woodworking-charts/?page=4


EDIT: Oooooops - that doesn't go above a #14, does it? Duh!! Sorry. That was pretty non-responsive, eh? :o Late night after the Tech v Tech football game [Hokies @ Ramblin' Wreck] - celebrating Tech's win................

My "rule of thumb" - To actually answer your question this time: calipers between the threads of a 1/4" lag screw show that the barrel itself is 3/16". The pilot hole's job is to remove the wood where the barrel goes, then you put the barrel in place of the displaced wood, and let the threads do their job. So - the pilot would be 3/16". If it was softwood, I personally would go slightly under that [by 1/64" or 1/32"]. If you are going up into end grain, I personally would undersize it a teensy bit as well. If I am going into hardwood long grain, I never undersize at all, and I always wax the screws.

hope that helps.

Kent



(http://www.woodmagazine.com/woodworking-tips/techniques/free-woodworking-charts/?page=4)

[Rich Engelhardt]

http://www.renovation-headquarters.com/lag-bolt-pilot-hole.htm

I use a 1/4" pilot and a 5/16" lag myself.
I've snapped too many 1/4" lags to be comfortable using them over 1" long.

[glenn bradley]

Proper pilot hole size is important for any screw. I will add to the chart supplied by Kent that for lags I drill about 1/4" longer than the screw's length. You don't want a fastener that size forcing its way into your material. Split material or a failed fastener can result.

[Rob Fisher]

I do what Kent does. Match the barrel size.

[Bill White]

Drill a hole equal to the "root size" of the screw-the dimension below the threads. I use a toilet bowl wax ring for a thread lube. Sure makes it easier to drive the screws/bolts.
Bill

[Kent A Bathurst]

I use a toilet bowl wax ring for a thread lube.

Bingo. I get the cheapest available, and smush it into a small, round, metal can with a lid. Stick the screws in it, and pull them out to drive. Every so often, re-smush it to fill the screws holes, get the air pockets out, and make a new flat surface.

In fact, mine is getting low - time to spend another buck or two, and reload for the next few years................