Submitted by Old-Designer-7909 t3_11bhaex in DIY
Got some spax yellox ones and planning on using them to hang a suspended ceiling. Each clip takes 4 screws and each 36kg 1.2mx1.2m plasterboard takes 12 clips.
Can't find any info online at all of sheer strength of this kind of screw.
Try searching for "shear" not "sheer".
the shear audacity for u to point that out
Spax screws usually have a chart on the box with shear strength values.
To calculate the shear strength of anything, look up the shear strength of the material: about 30 kpsi for carbon steel. Then multiply by the cross sectional area: M5=> ~4.1mm od = 0.161in od => 0.0205 in^2. So shear strength is 30,000 psi x 0.0205 in^2 = 610 lbs. Then divide by 4 for a safety factor. So place no more than 153 lbs per screw in shear.
Just trying to halp.
Laden, or unladen?
Got a mechanical engineering education and went into a slightly different engineering field for work. Never do stress analysis.
Except this exact one that comes up every so often around the house. 😆
Imperial, or metric?
Check here
https://spax.us/uploads/resources/DrJ_TER_No.2010-02_Construction_Screw_Properties_12-16-2021.pdf
Yer screwed
What do you mean? African or European
If you're hanging a ceiling, then you are probably more worried about the pull strength (straight out of the mounting material) of the screws, rather than the shear (sideways), compression (push) or tensile (stretched) strength of the screw itself. If driving into wood, the type of wood fixing is going to have a lot more bearing than the respective strength of the screws.
On the face of it, 36kg/12 screws = 3kg per screw. If the mounting surface can grip the screw sufficiently, any 5mm x 50mm screw will support this easily, in any dimension.
atheken t1_j9ya3oo wrote
Page 5 of this should get you an idea.
Selecting a similar size (in “freedom units”), a #6x2” is listed as having a shear strength of 265lbs. That’s about 120kg…
But just to be clear, you’re basically talking about 3kg per clip, and .75kg per screw, pretty sure you’ll be OK.
It’s not clear how the screws are mounted, if they are parallel to the tile, then you’re talking about shear strength, if they are perpendicular, you’re talking about tensile strength (and really, more concerned with “ultimate pull out load”).
But in either case, as long as you’re screwing in to something solid like a joist or stud, I wouldn’t worry about the screws.