If I can dig up this thread as well, thanks a ton @mmaner this is great info.
In addition to the excellent info on type, material, grades, and finishes, a gap in this discussion I noticed is appropriate torque values.
Especially when using fasteners on rotating machinery or in a vibration heavy environment (skateboarding being a perfect example), torquing down your fasteners can go a long way to keeping everything firmly affixed. Just about every fastener on your car, mountain bike, and motorcycle has a torque spec; why wouldnât you use the same philosophy on your board. Additionally, torque wrenches arenât very expensive, especially compared to the general cost of this hobby.
Machineryâs Handbook 26th Edition - Fasteners:
Tightening Bolts: Bolts are often tightened by applying torque to the head or nut, which causes the bolt to stretch. The stretching results in bolt tension or preload, which is the force that holds a joint together.
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High preload tension helps keep bolts tight, increases joint strength, creates friction between parts to resist shear, and improves the fatigue resistance of bolted connections.
If we want to get technical, measuring the elongation of the fastener while tightening is on average, a good bit more accurate than using a torque wrench, but thatâs not always physically possible or convenient.
Correct torque value is affected by many variables - ambient temp, lubrication, thread lockers, fastener grade and material, head type, finish, intended load, washers, etc.
That said, we can use a torque table to get more accurate than âhand-tightâ. Fastenal has a really thorough guide, broken out by size, head style, and material:
https://www.fastenal.com/content/merch_rules/images/fcom/content-library/Torque-Tension%20Reference%20Guide.pdf
Most common use case for us is probably the truck mounting bolts:
| SIZE | TPI | STYLE | MATERIAL | GRADE | Finish | Torque | Link |
|---|---|---|---|---|---|---|---|
| #10 | 32 UNF (Fine) | Button Head | Medium Carbon Steel | Grade 5 (120ksi tensile strength - medium) | Zinc | 48-60 in-lbs DRY* | McMaster-Carr |
| *This assumes youâre using locknuts, not loctite, and youâre adequately spreading the load with washers so you donât risk damage to the deck. |
If youâre concerned about any of your nuts rattling loose over time, or especially if youâve had issues before, you may try whatâs called torque striping/sealing. Itâs an instant visual indication of tightness. You can buy specialty high-viz compounds for this (or just start with a sharpie).
On a related note, this is why Iâve almost completely stopped using phillips or flat head fasteners - too easy to strip and you cannot reliably measure their tightness.
Note #2: When choosing screws, I generally aim for zinc-plated, alloy steel, hex drive. Theyâre higher strength than stainless, and zinc is a better coating than black oxide, which Iâve seen rust regularly in humid conditions.
This may be overkill, but itâs good to at least be aware of when and how to use a torque wrench. Hope it helps someone.