course thread stud - torque

[Mark L]

Can someone post the torque value for 3/16" and 5/16" course thread studs. These would be for mounting the prop governor and the SD-20 B&C Standby Alternator on the accessory pad (in my case).

Thanks

[Bob Kuykendall]

I think what you're looking for is in this table from AC43.13:



Thanks, Bob K.

[Mark L]

Thanks Bob but I think these are rather classfied as engine studs and are torqued to higher limits and fall somewhere around 200 in lbs for 5/16, but I am still unsure.

[alpinelakespilot2000]

Originally Posted by Mark L

Thanks Bob but I think these are rather classfied as engine studs and are torqued to higher limits and fall somewhere around 200 in lbs for 5/16, but I am still unsure.

Can't help you directly, Mark, b/c I'm not sure about that pad, but you are correct that engine studs are often torqued to a much higher spec than 43.13. The carb attach studs are one such place and were, I think, 200 in-lb. If I remember correctly, someone pointed me to a Lycoming manual and/or something at Sacramento Sky Ranch.

[Walt]

BOLTS, SCREWS AND NUTS (from the Lyc manual)

10 (3/16) = 49 in/lbs
1/4 = 96 in/lbs
5/16 = 204 in/lbs
3/8 + 360 in/lbs

[rzbill]

Mark,
I'm travelling and don't have these readily at hand. I got the Lycoming document from a post here on VAF. I think it was from Gil but maybe Mel.

Do a search and I think you will find the right doc. The studs you are using will be in the section on standard torques. There is a considerable listing of "special" torques, but the two pads you are fiddling with are not included in the special section.

I can attest that the Lycoming torque values will make your sphincter tighten up after being accustomed to the light AN values. I know $$ signs danced before my eyes while I was installing the prop governor. Its OK, they really mean them to be that tight.

EDIT ** Thanks for helping my neighbor, Walt

[az_gila]

Originally Posted by rzbill

Mark,
I'm travelling and don't have these readily at hand. I got the Lycoming document from a post here on VAF. I think it was from Gil but maybe Mel.

Do a search and I think you will find the right doc. The studs you are using will be in the section on standard torques. There is a considerable listing of "special" torques, but the two pads you are fiddling with are not included in the special section.

I can attest that the Lycoming torque values will make your sphincter tighten up after being accustomed to the light AN values. I know $$ signs danced before my eyes while I was installing the prop governor. Its OK, they really mean them to be that tight.

EDIT ** Thanks for helping my neighbor, Walt

Probably one of my posts. From the Lycoming overhaul manual - note the bit on lubricating the threads, unlike airframe bolts.

[chipf]

The table that Gil attached shows 204 in/lbs for bolts, but it's not clear if it applies to Lycoming exhaust studs, which are 5/16-18 on my O320-E2A. I used this number, which I found in another post a while back and now have the pleasure of installing Heli-coil repairs on at least one exhaust stud.

Larry Vetterman's page recommends a much lower number, 140 in/lbs, and that's more in line with the data that Bob K attached.

[Walt]

Exhaust stud torque is listed under "Special Torque Requirements" section:

5/16-18 Exhaust Port stud = 40 in/lbs min.

[az_gila]

Originally Posted by Walt

Exhaust stud torque is listed under "Special Torque Requirements" section:

5/16-18 Exhaust Port stud = 40 in/lbs min.

Is that for putting the stud in, rather than the nuts?

The exhaust system is usually an airframe item on a certified plane, so I checked my Tiger Maintenance Manual which gave 110 - 130 inch pounds for the exhaust flange nuts using new star lock washers - fitting in with the previous Larry Vetterman number.