Strength of a 1/2” screw eye?

[Seattlemusic]

I have four 1/2” screw eyes going into 2 x12s which are running perpendicular to 5x12 glulams holding up about 250 pounds total (hanging a cluster in a music studio). It seems rock solid but I have heard some say the break strength of ANY screw eye in wood of any type is 75 pounds. So yes technically it can hold it even with those numbers but not nearly at the safety margin I want. I will be sitting under this cloud/cluster often.

Curious if this is sufficient or if I should open up the ceiling and get up higher with a through hole or something that won’t have a risk of wood + bolt failure.

[J. Clarke]

numbers but not nearly at the safety margin I want. I will be sitting under this cloud/cluster often.

Here's a calculator that might be helpful

[Ed Pawlowski]

I found this:

1/2" diameter x 3-1/4" shank length, Hot Dipped Galvanized Screw Eye Bolt

Screw eye bolts are designed for screwing into wood. And because of this, do not have a working load limit assigned to them because it is not possible to determine the various densities and conditions of the wood the eye bolts are screwed into.

If I was sitting under 250# I'd probably use a thru bolt

[krw]

When I put in my hoists, I didn't trust screw eyes so added 2x8 beams across the room, sitting on the walls to take the weight. My jousts are "engineered" so can't take any suspended weight at all. The 2x6s allow me to put a 2x across them and use an eye-bolt and washer.

Whatever you do, make sure the fastener is rated for *lifting*. Most aren't.

[dpb]

A screw eye is more like a lag screw thread than an ordinary wood screw.

The maximum direct withdrawal load of lag screws from side grain of seasoned wood is

p=8100 G^(3/2) D^(3/4) L

where

p = Max withdrawal load, lbf D = Shank diameter, in G = Specific gravity of the wood based on oven dry weight and volume at 12% moisture content L = Length of penetration of threaded part, in.

For SYP assuming it is 1/2" shank (not clear) and 1" penetration, it's about 3,500 lbf for each.

If it is symmetrically-shared load, each is only about 60-65 lbf loading presuming your estimate of the total load is approximately correct.

Again, the above also presumes a properly-sized pilot hole and installation.

Can't really envision the physical arrangement of these 2x12 with respect to the glulams; are they inserts and if so, how are they being supported? There _might_ actually be the weak point, depending...