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I'm building a pot rack that will hang from my ceiling and I want to make sure it is secure. I rigged up a hanging apparatus that consists of a 1/2" x 12" bolt, two lock nuts, a 3/8" pipe floor flange, and two deck screws. The deck screws will be directly embedded into a solid ceiling joist.

I'd like to know generally, how much downward weight can a bolt like mine hold before the threads strip and fail. I'd also like to know the same thing regarding the deck screws. I couldn't find any sort of general chart or stats online. I included pics of my parts:

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    Deck screws are a dubious choice - this is a job for lag bolts.
    – Ecnerwal
    Commented Jul 13, 2019 at 3:10
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    Structural screws might be an option you can look at instead of those deck screws. They are used as an equal replacement to lag screws and then are smaller, thinner, and don’t require pre-drilling
    – UnhandledExcepSean
    Commented Jul 13, 2019 at 3:20

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The 1/2" bolts will hold up your truck, or thereabouts, so that's not an issue.

I'd be concerned about the pullout strength of the deck screws (especially if your rack was particularly big or you have a fondness for cast iron). Upgrade to something a little bigger. I'd lean toward a 1/4" lag screw, 3" or so, assuming that fits the flange. If that doesn't fit, aim for a #12 deck screw. Predrill pilot holes for the screws.

A little research... in typical conditions, you can expect a 2.5" fully threaded #12 screw to hold something like 300# in pine. See the calculator at engineering toolbox.

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Agree with banning deck screws for this. The lag bolts you used will be stronger than the joists you attached to, so I'd be more worried that the joists sag than that the bolts pull out. I'd suggest 3/8 or maybe even 1/4 lag screws, but make sure that you drill a small pilot before you sink the lags, or the joist may split and you have a much bigger project than you planned on. A possibility: span two joists with a 4x or 6x beam, and bolt your hanger to the spanner, that way you split the load to more than one joist.

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