JonJackjon t1_j26zqtd wrote on December 30, 2022 at 2:35 AM

Was the pre drill size from the mounting instructions?

As suggested I would pre drill deeper, drag the screw across a bar of soap before reinserting it. You might need a hand screwdriver for the last few turns.

huongdaoroma OP t1_j271maa wrote on December 30, 2022 at 2:49 AM

Update: Drill bit broke inside one of the screw holes while pre-drilling after advice. Can it hold 55 lb with only 3 of 4 screws (middle screw not used...)?

JonJackjon t1_j27g8oo wrote on December 30, 2022 at 4:43 AM

I would not venture to take a guess.

However if I were motivated to use only 3 holes I would purchase longer screws in stainless steel. The stainless steel part is important. It approximately doubles the tensile strength.

keestie t1_j27ne7o wrote on December 30, 2022 at 5:50 AM

I work construction. Stainless steel screws are terrible. They snap, bend, and the heads strip far more easily than normal steel. The only use for them is if you really need to avoid corrosion.

huongdaoroma OP t1_j27gfi0 wrote on December 30, 2022 at 4:45 AM

I'll just get drywall mud and redo it again with a Ryobi driver/impact set. Any suggestions for drill bit brands?

huongdaoroma OP t1_j2705lh wrote on December 30, 2022 at 2:38 AM

There actually wasn't a predrill size in the instructions if doing it in drywall>stud. The ones for brick/concrete gave a predrill size that included wall plugs (8mm/0.314 inch drill bit)

a2_d2 t1_j29fzxk wrote on December 30, 2022 at 4:43 PM

I always pre drill into stud if it’s any type of load bearing like this is. Just start from a small bit and increase size until youre approaching but still smaller diameter than the target screw. And you can use a regular (non power) screwdriver for the last few turns if needed. Good luck!