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hardware store bolts for 1st engine start

A

alwaysoutdoor

Active Member
I am getting close to my first engine start (probably in the next month or so) and was wondering if I could use grade 3 hardware store bolts for the catto propeller? I haven't bought the final bolts yet because I haven't done my Weight and Balance (no paint/engine baffling ect.) and don't know If I'll have to put a 20lb crush plate on the front like others here on VAF. Should I use these bolts or wait to start the engine until the very end of the build when I have the right propeller bolts? Thanks for the help!
 
Definitely not Grade 3 bolts. Grade 8 is more like it, but you'll still run into the differences between cut threads on the hardware store bolts vs rolled threads on AN bolts.

I fly with Grade 8 bolts in my prop, drilled their heads on the mill so they could be safety-wired. Couldn't source AN bolts of the proper length so had to make a compromise. Would still prefer to have the right rolled-thread AN bolts.
 
I'll use alternate or substitute materials and parts here and there. But I'd never operate the engine without proper fasteners on the prop. Very critical application.
 
Thanks everybody for getting me straight! I was leaning towards that side of the argument anyway. I would never try anything like that without asking of course! I guess I will just keep going on the windshield/baffles/cowling/paint and start up the engine for the first time once I buy the right bolts for crush plate and CG.
 
most hardware store bolts are rolled now days, it just cheaper to make them that way. The reason not to use them is that the thread design is different and the AN bolt is a lot stronger. most AN uses what's called a J thread. even though the yield strength may be the same on the bolt the J thread has a 40% higher fatigue strength and a 10% higher shear strength. you really do not want one of those cheap bolts loosing torque and damaging the hole on a prop.

bob burns
RV-4 N82RB
 
Bolts

From the sabermfg.com website:
Bolts are not "aircraft certified".
Hundreds of these in use. I prefer to use the term non certified rather than hardware store bolts.

Absolutely no reason not to use the non aviation bolts, not only for ground run, but permanently, as long as they are the proper quality.

In the 90's, some well known aerobatic airplanes were using grade 8 bolts for the main spar to fuselage attach. Hundreds if not thousands of hours on these airplanes with as much as 10 G each flight. AN bolts of that length and diameter were not available at that time.
 
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