MS21250 bolt torque values

[PhilLee]

I have a combination of the following bolt & nut (also some washers):
Bolt MS21250-05016
Nut H55LH4367-054

I have no direction in the SRM regarding the torque. While I have requested confirmation from the aircraft manufacturer, in the mean time I am trying to chase down something that can be of help.

Does anyone have a suggestion?

TIA

Phil

 

[israelkk]

You can find the MS here:

http://docimages.assistdocs.com/watermarker/transient/0E555DCE78B540F1BB12F9E59904F1D9.pdf

This is 180ksi rated bolt series for up to 450F degrees. For every bolt size you can find the ultimate tensile strength (force to brake) of the bolt in the last column of the table. I assume your bolt is 5/16" and for that size the minimum tensile strength is 11100 lbf.

You will need to calculate the bolt tightning torque such that the induced force in the bolt will be less than the break load of 11100 lbf with the desired factor of safety.

 

[GBor]

I see a note (E) that says "Wrenching element shall be in accordance with AS 870". It will take me a while to find AS 870 and see if it is of any use, but mathematically, you have a 5/16 in diameter bolt for a cross sectional area of 0.076in^2. If you can find the torsional allowable, you should be able to calculate the maximum torque.

 

[PhilLee]

FYI I realize that torque specs are part of the joint design but I guess I'm wondering if there is any relevant reference that may help. A stab in the dark I know...!

BTW if there are any c130 folks out there, this relates to the Main Landing Gear Beam to Drag Angle connection (STA577, RBL61.625, WL255 {approx}).

Phil

 

[PhilLee]

The hard copy of SAE AS 870 is available ($72.68) from IHS but I don't really have time to order it. The cost is not so much the issue...
Phil

 

[israelkk]

Here is MIL-HDBK-60 Threaded Fasteners - Tightening to Proper Tension

http://docimages.assistdocs.com/watermarker/transient/BD29897A7A5C483F9567A847B3BC94B6.pdf

 

[israelkk]

And here is NASA Fastener Design Manual

http://gltrs.grc.nasa.gov/reports/1990/RP-1228.pdf

 

[FieldTeam]

Wouldn't AC65-9A A&P General Handbook work?

Chapter 6 states that the standard torque table should be used as a guide in tightening nuts, studs, bolts and screws whenever specific torque values are not called out in the maintenance manual.

A 5/16 - 24, 160+KSI using any nut except shear type = 140-203 inch pounds.

 

[cedarbluffranch]

You need to wait until you get confirmation from the aircraft manufacturer. The amount of tension (preload) in a joint as compared to torque varies based on coatings of the nut, coatings on the bolt, thread size, pitch, nut material, and bolt material. The aircraft manufacturer likely has done testing of the nut/collar combination and will have exact data for you.

 

[FieldTeam]

"You need to wait until you get confirmation from the aircraft manufacturer."

Why wouldn't the standard torque tables/formulas be used in a situation where the torque is not called-out in the MM/SRM?

If he is working on a C-130 (and assume this is a military aircraft) then their T.O.'s will list the 1-1A-8 - Aircraft Structural Hardware, as applicable to this airframe.
There is a section in this TO that describes how to calculate torque if it is not given by the manufacturer.

AOG waiting for the aircraft manufacturer to give torque for standard hardware?

 

[PhilLee]

It is not a military C130 but rather a civilian L100-30.
We have resolved this particular issue but getting a copy of TO 1-1A-8 would be nice...
Phil

 

[FieldTeam]

What was the resolution?
Too many times people post here, then drop without finishing the thread.

 

[PhilLee]

We finally received specific torque values from the OEM...235-265 in-lb torque.

 

[cedarbluffranch]

Good solution! The OEM has extensive data on specific combinations of bolts and collars and that's the best way of ensuring that you are repairing the airplane to new condition. Using NASA references or other sources probably wouldn't pass DER muster.....

 

[HeviiGuy]

"Torque value", huh? On a very critical application at that, eh?

It saddens me that highly-educated people continue to put their faith into something which clearly has dubious or limited, at best, relationship to bolt load. :-(

There are so many variables which affect how much of the input torque actually results in bolt tension, yet many of us choose to remain oblivious to this reality. No wonder cranes collapse, reactors leak, wheels fly off of trucks, and airplanes fall out of the sky! C'mon, we all know that "Torque" is not and CANNOT be an indication of how "tight" a bolt is!

Tightening a bolt by applying "torque" (with a calibrated torque wrench even!) and then walking away, exepecting all to be fine, is almost negligent. Since "torque" has such an unknown relationship to a bolt's load, one must always take the next obvious step: measurement and verification. The easiest way of doing this is by measuring the stretch of the loaded fastener.

Ciao,

HevïGuy

http://www.heviitech.com