BobK207 wrote:
On Mar 29, 9:46 pm, Robert Allison wrote:

Pat wrote:

A 5/8" hole through a 4" wide beam reduces the load capacity by 1/4. Unless
your beam is oversized you may damage it enough to cause it to fail.

Please don't top post.

In addition, I would like to hear from the engineers in here
about the validity of the above statement. I do not believe it
for a minute. This is done quite often and I would be surprised
to learn that it compromises the integrity of the beam. Unless
you meant to say by 1/4 of 1 percent.




"MiamiCuse" wrote in message
...

I need to drill a 5/8" diameter hole through a laminated beam that is 16"
deep. This beam is sitting 10 feet above the floor across a room support
part of the roof. So I will be standing on a bench drilling from below
pushing the drill up.

I need this hole to be perfectly vertical as I will be passing a rod
through for a ceiling fan.

I know in the past when I had to drill through something much thinner like
a 2x4, I often end up with a slanted hole.

What can I do to ensure my drill is perfectly vertical?

I cannot afford to make a mistake and redrill.

Thanks,

MC

--
Robert Allison
Rimshot, Inc.
Georgetown, TX


Robert, I believe he's assuming that removing the hole material will
reduce the effective width of the beam & thus the load carrying
capacity.

I'm with Edwin & the others....drilling through the beam isn't a great
idea

but the actual capacity reduction depends on the beam width, the
location of the hole & whether the beam is currently bending stress,
shear stress or deflection limited (which depends on the depth & span)

for a 16" deep beam, the span has to be in the vicinity of 16' or so
(or greater) to be deflection limited....if the beam performance is
deflection limited then a 5/8" isn't going to change the deflection
performance that much. It will boost the local stresses so it should
be checked to make sure the allowable stress aren't exceeded.

cheers
Bob


Thanks, I was having nightmares about the dozens of beams that I
have either drilled holes through, or seen holes drilled through.
But then, almost all of my jobs have required an engineer to
write a letter for all of the oddities that the city just can't
stand to pass without professional opinions on paper. I think my
PEs would have mentioned something if I were compromising loaded
beams by as much as 25%.

--
Robert Allison
Rimshot, Inc.
Georgetown, TX