Spindle bolt torque

[Earthboundmisft]

I am finding conflicting numbers for the (dry) torque value on my grade 8, fine thread spindle bolt. Also some have suggested using a grade 8 mechanical locking nut instead of the typical castle nut / cotter pin. Can anyone with experience advise me, as the 'search' function has been little help. Thanks, Mike.

[GrantR]

You spindle bolt is aircraft grade correct? I though grade 8 was hardware store quality bolts.

[Earthboundmisft]

Grant, my hardware was purchased from East Coast Aircraft Supply, with paperwork.
AN-8. There seems to be some conflict on past threads regarding the proper grade
bolt for the spindle. My spindle bolt is a specific grip length, and was only available special order from ECAS. My rotor head is a Parsons.

[MikeBoyette]

Mike Dad uses grade 8 bolt and a grade 8 nylock nut. He replaces the nut about once a year. Not sure what torque should be but, I can check.

[Earthboundmisft]

Hey Mike, I would sure appreciate that torque spec, thank you. I read his thoughts regarding the nut, and took his advice. Interesting service interval. Mike H.

[edypaul]

Thats the first I've heard that you should change the spindle bolt nut once a year on a Dom? The estimated yield strengh of a grade 8 , 1/2 inch. bolt is about 19,000 lbs. Breaking strength is about 24,000 lbs.

[EI-GYRO]

AN-8 or Grade 8 ?????????

AN-8, surely.

I know, don't call me shirley.

[Earthboundmisft]

Shirley, thats where part of the confusion is. My understanding is that AN hardware is graded differently than SAE. The AN-8, is roughly a grade 5 in SAE terms. Obviously the
-8 is the diameter in 16/ths. I think Ernie uses GRADE 8 on his machines, which is overkill as previously stated. THEN, there are other differences beyond me, like ductility, hardness etc.:noidea:

[Earthboundmisft]

Oh yah, I am still looking for the proper torque for this rascal...

[docrob]

Grade 8 bolts have a spec sheet min tensile strength of 150,000 psi. AN8 (aircraft) bolts have a min tensile strength of 125,000 psi. The kicker is in the manufacturing process. Grade 8 bolts (may) have cut threads with a Class 2 fit. AN bolts WILL have rolled threads with a tighter (Class 3) fit, so the bolt/nut assembly of the AN bolt is stronger in tension, which is how a spindle bolt is loaded. In other words, the nut may pull off of a Grade 8 bolt easier than off of an aircraft quality bolt, even though the Grade 8 bolt is (maybe) stronger. Quality control is (presumably) higher in an aircraft bolt. AN8 twenty thread/inch bolts are torqued to 480 to 690 inch pounds, according to the Aircraft Mechanic's Handbook. All this information can be found on the web (that's where I got it!) I use AN bolts an all critical applications, and I consider the spindle bolt somewhat critical (DUH!) Also, if you are concerned about the torque changing in use, the MS17825 nut is a castellated nut with a fiber locking insert, which gives double safety, sorta like wearing a belt AND suspenders.

Dr. Rob

[JEFF TIPTON]

On the single seat Dominator, if the spindle bolt is the passes through the hub bar bearing and is an AN8-31, the torque is 480 to 690 inch pounds.

[edypaul]

I have never heard of a , AN8. There are grade 8 and AN bolts. No AN8 bolts.

[Passin' Thru]

I have never heard of a , AN8. There are grade 8 and AN bolts. No AN8 bolts.

Yes there are! AN 8 is an AN bolt 1/2" diameter. The "dash number" designates length of grip.

[edypaul]

Thats correct for the size of a bolt . He was refering to bolt strengh.

[edypaul]

I may have misread the post. I thought he was mixing An8 and grade 8 to some kind of fastener strength spec for an aircraft bolt.

[edypaul]

I am finding conflicting numbers for the (dry) torque value on my grade 8, fine thread spindle bolt. Also some have suggested using a grade 8 mechanical locking nut instead of the typical castle nut / cotter pin. Can anyone with experience advise me, as the 'search' function has been little help. Thanks, Mike.

My chart says for a Cad Plated 1/2 20 grade 8 bolt tightened to 60% of proof for Dynamic loads. Torque should be 83 foot lbs. If you use a self locking nut you should add the resistance of the nut to turn to the value of the tightening torque. Maybe someone here on the forum can verify these numbers.

[JEFF TIPTON]

Ernie show the AN8-31 bolt in his plans, not a grade 8 bolt. The torque is 480 to 690 inch pounds.

[Earthboundmisft]

JEFF, THANK YOU SIR, I was waiting for Mike Boyette to respond with the spec, and you beat him to it. You know... Im trusting you man, Mike H.:sad:

[Earthboundmisft]

Edwin, thanks for your input. Maybe this will help others too. Where do you work?

[edypaul]

I work for Continental Airlines in Orlando. You know, the sunshine state were it rains all the time! Ernie uses Grade 8 bolts in his rotor heads.

[Earthboundmisft]

Edwin thanks again, I THOUGHT Ernie used grade 8. I will torque accordingly. Hope your shop is busier than ours, part 135 is slow.

[edypaul]

They keep thinking of ways to spend money. Were installing Live TV in all our Planes so people can watch soap operas and Gerry Springer to pass the time .Our contract is up so they need to find ways to cry broke! Where are You At?

[Earthboundmisft]

Baer Air Charter, Melbourne Airport. We currently operate 10 aircraft. Its been slow for 6 months.

[edypaul]

Hang in there man! Its got to get better. It can't get any worse!

P.S. I love your Tail Art.

[edypaul]

If you're interested here is a web site that sells a CD called Mech tool box. with some good info for the Aviation Mech. Torque specs , Hardware info , Procedures and Tech stuff. http://www.mechanicsupport.com/index.html

[Earthboundmisft]

Edwin, I will check out that cd, thanks again.

[UtahBenson]

Good thread, I also needed that info..thanks.
edypaul, kinda pushing your luck with that statement cause I have found whenever you think it can't, it will !!

Hang in there man! Its got to get better. It can't get any worse!
P.S. I love your Tail Art.