Lag bolts that don't break?

Muhammad · Sep 20, 2020

I'm driving them into studs with an impact driver and I'm being fairly careful to not over-torque. I am pre-drilling but the holes are 1/8 and the bolts are 1/4 at the neck. Some broke off in the middle of driving them in. I guess I'm noticing this because I've done numerous projects before with lag bolts like this and even when I way over torqued them I never broke a bolt.

I have had great luck with construction screws in the past and in reality I probably don't even need the lag bolts for my kitchen shelves.

Tractor Seabee · Sep 20, 2020

The larger the lag bolt the more important are pilot holes the right size. View attachment Lag Bolts - Fastener Mart.pdf gives good info on lag bolts and their use. SS fastemers of all types are softer therefor more prone to breaking. Even wood screws need pilot holes especially the long ones. View attachment Bolt Depot - Pilot Hole Sizes for Wood Screws.pdf addresses these pilot holes.

Ron

oosik · Sep 20, 2020

I always predrill a hole if its a long lag bolt or long wood screw. Bar of soap on the threads and away she goes. I use an impact driver.

neverfailyou · Sep 20, 2020

I use lag bolts from TSC, drive them with battery impact driver, no pre-drilling. If I break one, it is usually because I drove it too much.

s219 · Sep 20, 2020

Muhammad said:
I'm driving them into studs with an impact driver and I'm being fairly careful to not over-torque. I am pre-drilling but the holes are 1/8 and the bolts are 1/4 at the neck. Some broke off in the middle of driving them in. I guess I'm noticing this because I've done numerous projects before with lag bolts like this and even when I way over torqued them I never broke a bolt.

I have had great luck with construction screws in the past and in reality I probably don't even need the lag bolts for my kitchen shelves.

I would think 1/8" hole for a 1/4" lag is the problem. You can get away with that in some soft wood (if it doesn't split) but not all. I have actually driven lags into soft white pine with no pre-drill at all, but the same technique is hopeless on yellow pine or any harder wood. If it's old wood, hard wood, or aged wood, you really need a large clearance hole. Let the threads bite and don't worry about the wedge effect (it's not a nail after all).

I remember once when renovating an old house, all of a sudden our regular tools seemed useless. Nail guns that worked everywhere else were having problems and basically bouncing off the wood. Construction screws that normally zip right in were struggling to gain a bite. Turns out the wood framing on that old house had gotten extremely hard and tough with age and heat. I realized that when I tried to drive a nail by hand and discovered the wood was hard as a rock.

I have seen the same problem with trusses up in attics. Due to heat, the wood up there gets very hard over time.

Tractor Seabee · Sep 20, 2020

Stay away from Phillips head screws, especially when using impact drivers. Long screws you want torque head.

Ron

Muhammad · Sep 20, 2020

Tractor Seabee said:
Stay away from Phillips head screws, especially when using impact drivers. Long screws you want torque head.

Ron

Yep! Agree completely.

The framing that I was lagging into was likely a contributing factor as it's from the early 80s, and although that's not super old those original studs did seem to be a bit on the hard side.

s219 · Sep 20, 2020

Muhammad said:
Yep! Agree completely.

The framing that I was lagging into was likely a contributing factor as it's from the early 80s, and although that's not super old those original studs did seem to be a bit on the hard side.

Oh yeah, 30-40 years is plenty old for wood to harden up, on the scale of things. It probably depends on the species/origin of the wood and the climate too.

3Ts · Sep 20, 2020

bcp said:
For more serious applications, I've been using this style.

CTX Construction Lag Screws

Bruce

pmsmechanic said:
GRK Fasteners | Home I haven't used these but have friends who have.

Structural Wood Screws Hidden Fastening Systems Timber Fasteners Look for the LOK line of screws. I have an assortment of these.

GRK uses a Torx driver and Fastenmaster uses a spline drive. I can't speak for the GRK but the LOK are very nice to use. The spline drive does not strip the way a robertson screw driver does in an impact driver. I no longer purchase lag bolts for use in wood.

Edited to add that I just looked through the Fastenmaster web site and it looks like they now use Torx drivers also.

I've used all of these and they work much better than the Lag screws. Lag screws (or Lag bolts) are made from soft steel and are not as strong as the new screws. There is a lot of improvements in materials, design, and coatings in these new screws. I do not use the actual Lag screws anymore. Some of these may still need a pilot hole drilled, especially if near the end of a board, even thou they are self-drilling.