Prop bolts....what's the consensus?

[stangflyer]

Any of you every change your prop bolts? If so, any particular reason? Any particular time? Any particular amount of flights? Any particular hardness? Other than soft Chinese of course. I am speaking of course for other than obvious reasons. Threads iffy and such. Speaking of threads on prop bolts, how much thread do you all like to see going into the prop hub? 1/4"? More?

 

[Ohio AV8TOR]

I buy a box of 20 from Fastenal or McMaster and always weight them to exact weight batches for use.  I do not change out on a frequency but I do from time to time.  Thread depth should always be at least 2x thread diameter so 1/4" is not enough. 5mm screw x2 = 10mm (0.393").  I always use a torque wrench as well.  Torque is a whole other subject.   

 

[stangflyer]

Ohio.AV8TOR said
I buy a box of 20 from Fastenal or McMaster and always weight them to exact weight batches for use.  I do not change out on a frequency but I do from time to time.  Thread depth should always be at least 2x thread diameter so 1/4" is not enough. 5mm screw x2 = 10mm (0.393").  I always use a torque wrench as well.  Torque is a whole other subject.   

Hmmm!!!! Not questioning your knowledge a bit.... but just curious. How do you come up with the formula of thread depth? I had a Falcon 32x10  but due to my SUPIDITY I had to replace it and all I could find was a 32x11. The 157 turns it fine, but not like it turned the 32x10. So, I have a PT Carbon Fiber 32x10 I was going to swap it out for. But the PT is much thicker at the hub than the Falcon. Prop bolts are only giving me about 1/4" of threads in the hub. Hence my questions.

 

[Terryscustom]

Yes change out, I do every 5 times I have the prop off (with carbon props).      Reason is they stretch and get weaker.      I get boxes of 20-25 from McMasters because Fastenal wants an arm and part of a leg for them.     I also use nord-lock fasteners on the prop bolts instead of lock washers for a little added security.      Washers are expensive but especially the stainless ones can be used countless times.     Rule is 2-2.5 times the dia.    I normally shoot for 1/2-5/8" minimum with 3/4 being my goal.     Class 12.9 seems stronger than most bolts included with engines, I even replace the ones included with my DA's after a couple times of use:     http://www.mcmaster.com/#catalog/120/3094/=ucjdg6

 

[Terryscustom]

Ohio.AV8TOR said
I buy a box of 20 from Fastenal or McMaster and always weight them to exact weight batches for use.  I do not change out on a frequency but I do from time to time.  Thread depth should always be at least 2x thread diameter so 1/4" is not enough. 5mm screw x2 = 10mm (0.393").  I always use a torque wrench as well.  Torque is a whole other subject.   

The actual general rule in engineering is the engagement should be equal to or greater than one times the dia. of the fastener.      But the common sense rule of thumb is two times the dia. for fasteners under load.      In our case we have load and vibration so I would never fly with 1/4" of threads in the hub.

 

[stangflyer]

Terryscustom said
Yes change out, I do every 5 times I have the prop off (with carbon props).      Reason is they stretch and get weaker.      I get boxes of 20-25 from McMasters because Fastenal wants an arm and part of a leg for them.     I also use nord-lock fasteners on the prop bolts instead of lock washers for a little added security.      Washers are expensive but especially the stainless ones can be used countless times.     Rule is 2-2.5 times the dia.    I normally shoot for 1/2-5/8" minimum with 3/4 being my goal.     Class 12.9 seems stronger than most bolts included with engines, I even replace the ones included with my DA's after a couple times of use:     http://www.mcmaster.com/#catalog/120/3094/=ucjdg6

Thank you.... Really glad now I asked the questions I did.

Guess I am ordering prop bolts.... 

 

[ericb]

Terryscustom said

Yes change out, I do every 5 times I have the prop off (with carbon props).      Reason is they stretch and get weaker.      I get boxes of 20-25 from McMasters because Fastenal wants an arm and part of a leg for them.     I also use nord-lock fasteners on the prop bolts instead of lock washers for a little added security.      Washers are expensive but especially the stainless ones can be used countless times.     Rule is 2-2.5 times the dia.    I normally shoot for 1/2-5/8" minimum with 3/4 being my goal.     Class 12.9 seems stronger than most bolts included with engines, I even replace the ones included with my DA's after a couple times of use:     http://www.mcmaster.com/#catalog/120/3094/=ucjdg6

+1 on the nordlocks. They work great and really hold tight.

 

[stangflyer]

I honestly had not heard of these... Nord-lock systems. So I of course went to the ole' trusty youtube. This is what I found. I'm sold. Although I've not experienced any issues of my bolts loosening on any of my motors and to that, I've heard of prop bolts shearing, props coming off, vibrating etc., I thing now I have been VERY fortunate. Definitely ordering some nord-lock washers and a box of bolts. Thanks very much everyone.... I do appreciate it greatly. (Amazing the things a guy can learn if he is just willing to open his mind huh?)

https://www.youtube.com/watch?v=mgwmuZuJ02I

 

[tylerzx9r]

You just happened to ask the right questions! Then fortunately got the good people of the media to answer you with correct and good knowledge. There are a ton of people out there that would have filled you full of crap and had you second guessing yourself for weeks! So far that hasn't been too much of an issue from haters out there on this site! I will tell you I also have been fortunate enough to not have a problem on my own planes, but have seen to close to failure problems of bolts breaking, and I personally seen them torque them and do everything your supposed to. So better safe then sorry!  

 

[stangflyer]

tylerzx9r said
You just happened to ask the right questions! Then fortunately got the good people of the media to answer you with correct and good knowledge. There are a ton of people out there that would have filled you full of crap and had you second guessing yourself for weeks! So far that hasn't been too much of an issue from haters out there on this site! I will tell you I also have been fortunate enough to not have a problem on my own planes, but have seen to close to failure problems of bolts breaking, and I personally seen them torque them and do everything your supposed to. So better safe then sorry!  

Well, that being said... I promptly went down to my local Tacoma Screw this afternoon. Not only did they have the nord-lock washers, but they also had the right length 12.9 hardness bolts to replace the ones I have been using. As it stands, Terry mentioned he likes to shoot for 3/4" of threads inside the hub. Yup.... right at that very figure. Six new bolts, six new nord-lock washers and she's ready to rip again. I bought extras for back up. Now that was thinking huh? LOL