Lag Screws

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jmellc

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Location
Durham, NC
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Facility Maintenance Tech. Licensed Electrician
I may have to find another place to buy lag screws. I installed a strut yesterday with 2 1/2 inch galvanized lags I bought at Big Blue. Popped the head on 3 & I know I wasn't turning that hard. Popped about where the threads begin, 1/2" or so from head. I see that with toggle bolts too sometimes.

Maybe Fastenal has a better quality screw. None of our local supply houses usually have lags.
 
I don't think lag bolts use the head marking code you find on machine bolts.

I stopped using ordinary lag bolts over a decade ago. Instead, I use the ones made by Simpson Strong-tie, and usually stocked with the Strong-tie connectors, rather than in the nuts & bolts aisle.

The Simpson bolts have washered hex heads, which are a natural for driving with an impact driver.
 
renosteinke said:
I don't think lag bolts use the head marking code you find on machine bolts. ...
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Understanding and correctly using the marking code is a small science in itself. JMO

Lag bolts are cast not rolled or machined that one finds at a big box store.
 
GUNNING said:
I watched a lineman nail one in with a hammer instead of using a ratchet. Worked pretty well. That was before battery impact drivers.
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I haven't seen many hammer type lags in recent years. We used to use them in the 70's to mount pole lights & other things. They usually had a square head & threads were long spiral type, more like a spiral shank nail.

Next time I'm near Fastenal, I'll see if they have galvanized lags & buy a small box or bag of them.
 
GUNNING said:
I watched a lineman nail one in with a hammer instead of using a ratchet. Worked pretty well. That was before battery impact drivers.
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The ones that they do that with are designed for that. They are harder steel and threads are designed to slip into the pole easier but will need to be turned to remove them.

Try doing that with typical hardware store lags in a hard new pole and you will only enter the pole slightly and will probably eventually break the bolt.
 
Cow said:
Are you predrilling?
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Yes, a size below 3/16", for a 1/4" lag. 5/32" I think. I always drill for anything larger than #12. They all snapped about the same place, about a 1/4" before the threads.
 
jmellc said:
Yes, a size below 3/16", for a 1/4" lag. 5/32" I think. I always drill for anything larger than #12. They all snapped about the same place, about a 1/4" before the threads.
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I am guessing you are also putting them into some pretty hard wood, most general purpose construction lumber is soft enough you shouldn't have much trouble installing a lag screw. Engineered framing members can be very hard as they usually have a high density as compared to natural wood.
 
kwired said:
I am guessing you are also putting them into some pretty hard wood, most general purpose construction lumber is soft enough you shouldn't have much trouble installing a lag screw. Engineered framing members can be very hard as they usually have a high density as compared to natural wood.
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Mounted a strut to the outside roof facia board on a mobile home. Have to get attachment point out a ways to keep incoming triplex from hitting the roof edge. I put a long eye bolt (from POCO) into a 7/8" strut about midway. Strut is 3 feet. I drilled a large hole for the bolt/nut to rest into the wood, put 3 lags either side to further support the eye bolt. Lags go through 1/2" plywood facia into a 2 x 4. Being a mobile home, I doubt the 2 x 4 being anything other than standard #2 stud. It is not new, so it may have seasoned a little in the sun for 2-3 years. But drilling it was no problem.
 
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I was napping in my office one day when one of our shop guys came into complain about a bunch of defective bolts I ordered. I go out and watch him break the head of off several of them. I ask him what he is torquing them to, and he says some number. I look it up and that is the right number and he has it set right on the torque wrench.

So I try it myself. Works fine.

He tries it again and snaps another one off.

I am getting nervous, thinking there is a bad lot of bolts UNTIL I watch what he is doing real close. He was using the kind of torque wrench that just breaks a little when it hits the right torque but than tightens up again about 5 degrees later. He just kept going.
 
petersonra said:
I was napping in my office one day when one of our shop guys came into complain about a bunch of defective bolts I ordered. I go out and watch him break the head of off several of them. I ask him what he is torquing them to, and he says some number. I look it up and that is the right number and he has it set right on the torque wrench.

So I try it myself. Works fine.

He tries it again and snaps another one off.

I am getting nervous, thinking there is a bad lot of bolts UNTIL I watch what he is doing real close. He was using the kind of torque wrench that just breaks a little when it hits the right torque but than tightens up again about 5 degrees later. He just kept going.
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These lag bolts don't come with any torque specs. There may be some in the factory office, but not posted at the retailer. I just predrill & turn until flush, then snug up by feel. I have lost a lot of strength in my hands/arms, so I'm sure I'm not doing the King Kong thing on them. I have been plenty guilty of that in the past.:)
 
Breaking off heads ...

My weekend work reminded me ... I hardly ever break off heads since I started using an impact driver, rather than a drill / screwgun. Even a small impact driver will drive 1/4" lags with ease.
 
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