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Will 3 out of 4 lag bolts secured to studs hold a wall mount with a 45 lb 40" LCD TV?

post #1 of 14
3/27/12 at 9:50pm
Thread Starter 
Will 3 out of 4 lag bolts secured to studs hold a wall mount with a 45 lb 40" LCD TV? One of my four bolts snapped off in the wall while hanging my wall mount plate (lower right corner bolt of plate); the other three are solidly in the studs 16" apart. Realistically should this be a problem holding a 45 lb. LCD Samsung 40" TV? Here is the wall mount I'm using:

It's product # 8587 on Monoprice (I can't yet post the URL since this site won't let me).

I tried extracting the bolt from the wall with an extracting bit without luck. Let me know your thoughts, thanks!
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post #2 of 14
3/27/12 at 11:55pm
Did you pre-drill the holes before driving the bolts in?

My worry would be if one bolt broke, could the others have also suffered some stress from being driven in without a big enough pilot hole.
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post #3 of 14
3/28/12 at 5:08am
Thread Starter 
Thanks for the reply, Sebberry. Yes, I did pre-drill all four of the holes with a 5/32 (4mm) drill bit, which is the size Monoprice's instructions say to use for the M8x90 lag bolts they included. The instructions say to drill the holes 3" deep. I may have only gotten them a little over 2.75 inches deep due to my bits not being long enough, so I'm not sure how much of an impact that would have.

I tried drilling a new hole through the plate above the broken bolt's hole but I can barely put a dent in the steel. Is there a special drill bit recommended for drilling a holt through a steel plate?
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post #4 of 14
3/28/12 at 6:15am
Quote:
Originally Posted by wildclay View Post

Thanks for the reply, Sebberry. Yes, I did pre-drill all four of the holes with a 5/32 (4mm) drill bit, which is the size Monoprice's instructions say to use for the M8x90 lag bolts they included. The instructions say to drill the holes 3" deep. I may have only gotten them a little over 2.75 inches deep due to my bits not being long enough, so I'm not sure how much of an impact that would have.

I tried drilling a new hole through the plate above the broken bolt's hole but I can barely put a dent in the steel. Is there a special drill bit recommended for drilling a holt through a steel plate?

I think 3 bolts should be fine.

But I snapped a bolt before and just redrilled a hole above it. You need a good metal bit (gold colored bits work for me) and use high speed if your drill has low and high.

I have a Ryobi 18volt cordless that went through the plate like butter. You should nor have that much trouble with the right bit.
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post #5 of 14
3/28/12 at 1:26pm
Thread Starter 
Thanks for your input, Hockeypuck25! Was the wall mount plate you drilled through a Monoprice mount? The steel on my mount (Monoprice product # 8587) is pretty tough, but I only have bits made for wood (and concrete, but that those slide right off the metal). I was barely able to put a dent in the plate after 10 minutes of high-speed drilling at it.

Do you or anyone else have any suggestions for extracting a M8x90 lag bolt from half an inch in the wall? I bought an extraction kit, but like the mount plate, the bolt's steel is too tough for me to drill a pilot hole into the center of the broken bolt. I'm hoping a good metal drill-bit set will also aid in this in addition to possibly trying to drill a new hole in the plate.
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post #6 of 14
3/28/12 at 7:34pm
Quote:
Originally Posted by wildclay View Post

Thanks for your input, Hockeypuck25! Was the wall mount plate you drilled through a Monoprice mount? The steel on my mount (Monoprice product # 8587) is pretty tough, but I only have bits made for wood (and concrete, but that those slide right off the metal). I was barely able to put a dent in the plate after 10 minutes of high-speed drilling at it.

Do you or anyone else have any suggestions for extracting a M8x90 lag bolt from half an inch in the wall? I bought an extraction kit, but like the mount plate, the bolt's steel is too tough for me to drill a pilot hole into the center of the broken bolt. I'm hoping a good metal drill-bit set will also aid in this in addition to possibly trying to drill a new hole in the plate.

Is the bolt snapped flush with the wall? Or is it sticking out slightly?
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post #7 of 14
3/28/12 at 9:24pm
Thread Starter 
Hi Foley_49, thanks for asking. The bolt is actually broken off about a quarter inch inside the wall, so neither flush nor sticking out. I can see the snapped end when I look in the hole.
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post #8 of 14
3/29/12 at 6:22am
If you snapped the bolt while putting it in, I would go to the hardware store and buy 3 new lag bolts and replace the existing 3, then hang the TV and enjoy.
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post #9 of 14
3/29/12 at 10:19am
Quote:
Originally Posted by wildclay View Post

Thanks for your input, Hockeypuck25! Was the wall mount plate you drilled through a Monoprice mount? The steel on my mount (Monoprice product # 8587) is pretty tough, but I only have bits made for wood (and concrete, but that those slide right off the metal). I was barely able to put a dent in the plate after 10 minutes of high-speed drilling at it.

Do you or anyone else have any suggestions for extracting a M8x90 lag bolt from half an inch in the wall? I bought an extraction kit, but like the mount plate, the bolt's steel is too tough for me to drill a pilot hole into the center of the broken bolt. I'm hoping a good metal drill-bit set will also aid in this in addition to possibly trying to drill a new hole in the plate.

Yes, it was a monoprice mount for a 52" LCD. I just left the bolt in the wall because it was under the sheetrock. Dont waste your time. The bit I used came in a Ryobi drill kit like this one. The gold bit is what you need.

http://www.homedepot.com/Tools-Hardw...&storeId=10051

And it is not a case of bad bolts. I have snapped all kinds of bolts due to overtorquing. You really need to make sure you drill a good pilot hole first. There should be some resistance up until about the last few threads. If you are fighting it the entire way, you need to ream the hole a little more.
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post #10 of 14
3/29/12 at 9:28pm
Quote:
Originally Posted by airscapes View Post

If you snapped the bolt while putting it in, I would go to the hardware store and buy 3 new lag bolts and replace the existing 3, then hang the TV and enjoy.

That's a great idea. Can you move the mount a quarter inch up or down?

If you think 3 may be adequate, then hang on the mount - lift your feet up. Try to pull it down.

It's the Big Boy Test. Find an obese friend, if you're not up for the challenge.
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post #11 of 14
3/30/12 at 1:32am
2 Bolts would have held a tv that size with a mount designed for a single stud.
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post #12 of 14
3/30/12 at 5:31pm
I had a similar situation. Three lags held my 46" for 5 years till I took it down. I tested it by hanging on it. Lags into studs are very strong.
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post #13 of 14
4/3/12 at 12:29pm
I always remember being told to use a soap bar to lubricate the threads of the lag bolt before driving it in, but a quick googling brings up worries about rust. Beeswax or vegetable oil is recommended.
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post #14 of 14
4/3/12 at 1:22pm
Quote:
Originally Posted by Hockeypuck25 View Post

If you are fighting it the entire way, you need to ream the hole a little more.

That's what she said! Sorry, I just couldn't resist.
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