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why are these 1/4" lag bolts snapping??

1619 Views 38 Replies 29 Participants Last post by Andybb, Apr 20, 2022

Ross1985

Discussion Starter · Apr 18, 2022 (Edited by Moderator)

4

I'm mounting a rack in my garage. I am using 1/4" lag bolts that are 2.5" long I purchased from Home Depot. The lag bolts go through the rack bracket holes in the photo below, through 1/2" drywall and into 2×10 floor joists above. I drilled a 3/32 pilot hole first. I used my impact driver and the bolt snapped about 3/4 of the way through. I switched to just using a ratchet, thinking maybe it was the impact driver, but the same thing happened. Any thoughts on why this is happening?

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BurlyBob

· #2 · Apr 18, 2022

I'm going to say cheap Chinese metal.

syenefarmer

· #3 · Apr 18, 2022

Double check the depths of the pilot holes to ensure they're deep enough would be my first guess. If that isn't the issue then I'd look somewhere else for a source of higher quality lag screws than the big box store.

LesB

· #4 · Apr 18, 2022

I would think 3/32nds pilot is too small. I would go to 5/32nds or even 3/16 if the wood is hard.

Also it may be the unthreaded section of the bolt is hitting the wood before the bolt is tight and is unable to compress it to go in any further. In that case you may want to expand the first part of the pilot hole to 1/4", where that unthreaded part of the bolt enters the wood.

gtrgeo

· #5 · Apr 18, 2022

I agree with the cheap Chinese metal. I have had the same issues with the lag bolts like you are using. I have gone to using the SPAX or GRK lag bolts and have found them to hold up much better. They cost a little more but are well worth it.

controlfreak

· #6 · Apr 18, 2022 (Edited by Moderator)

Check the pilot hole and wax or soap the bolt threads. Might want to source the bolts with a better hardness rating too.

AlaskaGuy

· #7 · Apr 18, 2022

According to the charts, 3/32 is the right size for softwood and 3/16 for hardwood. Have you tried using a lube like bees wax?

1thumb

· #8 · Apr 18, 2022

SPAX or GRK

- gtrgeo

+1

northwoodsman

· #9 · Apr 18, 2022 (Edited by Moderator)

They make many different grades of bolts including lag bolts. I'm not an expert on the grading system but I'm sure someone with knowledge will chime in shortly. I'd go with at least 5/16" but most likely 3/8" lag bolts.

Unknowncraftsman

· #10 · Apr 18, 2022

Pilot hole is too small for cheap lags. I drill holes always for the root part of the screw.

redlee

· #11 · Apr 18, 2022

I refuse to ever buy Lags again, as said before Spax ,GRK.

gdaveg

· #12 · Apr 18, 2022

I agree with the cheap Chinese metal. I have had the same issues with the lag bolts like you are using. I have gone to using the SPAX or GRK lag bolts and have found them to hold up much better. They cost a little more but are well worth it.

- gtrgeo

After you use GRK Screws you will be amazed and swear off true lags.

But, if wood is hard online source says 3/16" pilot hole.

The commercial guys use a special drill that is stepped, drills pilot and lead hole at the same time.

EdDantes

· #13 · Apr 18, 2022 (Edited by Moderator)

You may need to drill the first part of the hole (equal to the length of the unthreaded shoulder) for the full diameter (1/4"). That would be corroborated if the screws are threaded 3/4s of the way…

https://www.finehomebuilding.com/2003/09/01/pilot-hole-sizing-for-lag-bolts

Alternatives would be to use fully threaded lag screws, or switch to a lag alternative as people have suggested.

JIMMIEM

· #14 · Apr 18, 2022

After drilling the initial pilot hole, drill the hole again to the depth of the smooth part of the bolt. If the smooth part of the bolt is a true 1/4" then use a 1/4" drill bit for this portion of the hole. Bolts come in different hardnesses. If you want harder bolts you may have to go to a good hardware store and go for maybe a Grade 8 bolt. Be careful if your impact driver doesn't have clutch settings or you may strip out the hole.

Knockonit

· #15 · Apr 18, 2022

lubricant, and drill correct hole size, we use the snot out of them, no issues, other than an occasional mishap like this,
and as noted lotsa other options also,

what amazes me is that folks do this to the bottom chord of a truss that is meant to hold no more than a few pounds per sq ft and load the sucker up with a lot of weight, heres hoping the truss manuf. did a good job
Rj in az

AlaskaGuy

· #16 · Apr 18, 2022 (Edited by Moderator)

lubricant, and drill correct hole size, we use the snot out of them, no issues, other than an occasional mishap like this,
and as noted lotsa other options also,

what amazes me is that folks do this to the bottom chord of a truss that is meant to hold no more than a few pounds per sq ft and load the sucker up with a lot of weight, heres hoping the truss manuf. did a good job
Rj in az

- Knockonit
</blockquote

He said Joist, not the bottom of a truss. He also said 2×10. Makes me think these are floor joist over his garage, for a room above
https://findanyanswer.com/how-much-weight-can-i-hang-from-a-floor-joist

therealSteveN

· #17 · Apr 18, 2022

4

This is my lumber rack. It currently has a few thousand bd/ft of lumber, and other odds and ends on it. I'd guess a few tons.

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It's held together, and mounted to the wall with a mix of 1/4" Lags, and 1/4 20 bolts. I have never drilled a pilot hole since I started using this tool to drive lags, Just hit to go switch, and walk them right in. I've never broken a lag. Been making frames, shelves, and all sorts of benches 2x material built, over the last 45 years, and have never broken a lag.

I buy my hardware from Tractor Supply now, it's good stuff for a fraction of the price of what they sell at the BORG's

My insert tool is this, with a socket to fit the head of the lag. I think it's the rattling that allows the lag to just walk on in.

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Knockonit

· #18 · Apr 18, 2022

lubricant, and drill correct hole size, we use the snot out of them, no issues, other than an occasional mishap like this,
and as noted lotsa other options also,

what amazes me is that folks do this to the bottom chord of a truss that is meant to hold no more than a few pounds per sq ft and load the sucker up with a lot of weight, heres hoping the truss manuf. did a good job
Rj in az

- Knockonit

[/QUOTE]

oops didn't read it all, either way, a load not intended, i'll remember to read in detail next time. thanks for pointing out.
i have a crew that all they do is repair trusses, amazing what folks belief is structual,

timber screws we use in framing a lot, simpson makes a gaggle of them.
hope it works out.
rj in az

ibewjon

· #19 · Apr 19, 2022 (Edited by Moderator)

Spax, GRK are great. Both have wide threads, and a smaller, harder shaft. They don't make lags the way they did in the past. I have never seen a grade 5 or grade 8 lag screw, no matter where I shop.

JohnDon

· #20 · Apr 19, 2022

In the OP's photos the breaks occur in the threads. If the pilot hole is too narrow for the unthreaded section, the break would have to be somewhere between there and the head, so that's not the reason. I say poor quality steel; lube might help.

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