Warp HP-L blade clamping bolt size?

[dholly]

Re: Warp Drive 3-blade prop w/ HP-L hub on 912ul.

While re-torqueing my prop and 1/4" blade clamping bolts I discovered galling on a few of the clamping bolts so I'm replacing all. Unfortunately, I can't find a definitive size for the clamping bolts in my docs, on the Warp site or here, and I don't have an old bolt handy.

Can anyone confirm my best guess of AN4-20A please? Tnx

[Dave S]

dholly,

Your best bet, if you don't have an old bolt to measure, is to call up Warp. A person would like to think they are all the same....but that never seems to work so I don't want to venture a guess based on my setup.

If you can give Warp your model and serial # I am sure thay can provide the correct dimension. I have found they are pretty good at answering questions about their products.

Otherwise, measure your hub with a washer and nut sitting on the one side and pick a bolt size that will give you 1-3 threads beyond the end of the nut. Make sure the grip length is less than the thickness of the hub. FYI AN bolts can vary in length by +/- 1/32" but that isn't normally a factor in measuring.

Sincerely,

Dave S
KF7 Trigear
912ULS Warp Drive

[dholly]

Thanks Dave, but Warp is closed today and my hub is offsite with the plane. Warp simply lists "Clamping bolts, nuts, washers--per blade" for the 3-blade HPL hub, so I believe all 3-blade HPL hubs take the same size bolts. Like to get an order in today so I was just hoping someone here had the size and could save me the trip.

[dholly]

Been meaning to come back and leave the info for future reference. Pretty sure the old bolts were AN4-20A (2.031" Length x 1.562" Grip). I think they were too long with a single washer under the nut, felt like the nut was bottoming out on the threads when we were torquing it. Same size new with two washers under the nut still felt questionable to me so we ended up using AN4-17A (1.906" Length x 1.438" Grip) with a single washer.