NR prop bolt concern

[avidflyer]

The NR bolts had an 8.8 marking on the heads. JImChuk

[jrevens]

The NR bolts had an 8.8 marking on the heads. JImChuk

If that marking denotes a grade 8 bolt (I don’t know if it does - are they metric?) then those bolts are likely supposed to have a greater tensile strength than a normal AN bolt. AN bolts are roughly equivalent to a grade 5. NAS bolts are available in higher strength than AN bolts also.

Just as an aside, I know that a few American wood prop makers used to specify stronger industrial bolts for their props also. Coming from trusted US manufacturers, they were usually equivalent to grade 8.

[Av8r3400]

If that marking denotes a grade 8 bolt (I don’t know if it does - are they metric?) then those bolts are likely supposed to have a greater tensile strength than a normal AN bolt. AN bolts are roughly equivalent to a grade 5. NAS bolts are available in higher strength than AN bolts also.

Just as an aside, I know that a few American wood prop makers used to specify stronger industrial bolts for their props also. Coming from trusted US manufacturers, they were usually equivalent to grade 8.

8.8 is NOT a grade 8 bolt. It is a metric designation closer to an SAE grade 5.

I ordered special size metric 8.8 hardware for mine that attached into the metric threaded hub inserts. I needed longer hardware for the prop spacer, balance ring and the prop hub. I put the bolts into my milling machine and cross drilled the heads for safety wire.

Metric-Bolt-Grades-Compared-to-SAE-metric-bolt-grades-vs-SAE-DGMF-Mold-Clamps-Co.-Ltd.jpg

https://www.engineeringtoolbox.com/m...html#gsc.tab=0