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.
If it were me, I would drill the hole through the beam, then hang
the ceiling fan from the beam and use the hole for just the wire.
In the off chance that you MUST do it like you are stating, then
there isn't really an inexpensive method of making SURE that it
is perfectly plumb. I would assume that you are using an auger
bit. If so, then you can take a block of wood say six inches
thick and, using a drill press, drill a hole straight through the
block. You can then use the block as a guide for your drill bit
to hold it square with the bottom of the beam.
I have also used torpedo levels to line up my auger bit, then
drilled by hand, checking every so often with the level to make
sure my bit is plumb. When I can't get the level on it anymore,
then it will usually guide itself the rest of the way.
I wouldn't invade the beam at all- I'd build a hollow 'U' out of
matching wood that fits over the beam from below, and trim out so it
looks like it belongs there. If the beam is sloped, you can make it look
like the added block was for purpose of giving a flat mounting point.
Hard to give good options without seeing it.
16" is a long way to drill "perfectly straight" by hand.
I also assume you're using an auger bit (at least 18 to 24" long)
Got any of the glulam left over? Practice.
Hot gue or "affix" in some manner two framing squares at 90 deg to
each other & parallel to the axis of the hole to be drilled.
Use he square to eyeball the straightness of the hole, a "spotter" is
....drilling the hole a bit over sized (3/4") will give you some
per Robert's suggestion why not just drill the hole for wiring &
figure to do the mechanical mounting a different way. A 5/8"
"nutplate" would do the trick.
Personally I would avoid drilling through the beam that way and would
instead hang the fan along the side of the beam. If I were going to the
trouble of deep drilling through the beam, I would be going large enough
to feed 1/2" rigid metal conduit through to allow the power to feed
through "invisibly". With a beam like that you can support a fan rated
box from the beam with a couple lag screws if you're going to be routing
power to the box along the beam anyway.
A perfectly made 16"-deep hole will be difficult to make, and how to
keep a hand-held drill plumb and steady is another problem. Perhaps,
clamp a table-top drill press to the beam and use various length 5/8"
Could you make 3 sided jig?
Start with 2 vertical pieces of wood clamped to the beam.
If the beam is wider than the drill body, use filler strips below the
beam. If the drill body is wider than the beam, the filler strips
would go between the beam and the vertical pieces.
The idea is to sandwich the drill body so it cannot swing side to
Once this "channel" is in place, close off the back side with a board
so you can put the back of the drill body against it to prevent back
and forth movement.
If the drill can't go side to side or back and forth, your hole should
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.
Robert, I believe he's assuming that removing the hole material will
reduce the effective width of the beam & thus the load carrying
I'm with Edwin & the others....drilling through the beam isn't a great
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.
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%.
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