Threaded Fastener Torque in 6061-T6 Aluminum

[michaelbarclay]

All the information that I can find on recommended threaded fastener
torques and corresponding clamp loads are based on the proof load of
the screw, not the material that it is screwed into.
Where can I find information on the recommended torque of a fastener
being screwed into a 6061-T6 Al plate? Also the coresponding pull out
load (i.e. at what load do the threads strip in the aluminum)?


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[Jeff Finlayson]

michael barclay wrote:

> All the information that I can find on recommended threaded fastener
> torques and corresponding clamp loads are based on the proof load of
> the screw, not the material that it is screwed into.

> Where can I find information on the recommended torque of a fastener
> being screwed into a 6061-T6 Al plate? Also the coresponding pull out
> load (i.e. at what load do the threads strip in the aluminum)?

You should be using an insert. But since you aren't..

The thread shear strength is a function of part thickness, ie number
of threads carrying load.

You need to perform a preloaded bolted joint analysis. Calculate
the preload and combine with external loads.

Some references:
Mechanical Engineering Design by Shighley
Bolted Joints (something like that) by Bickford
Criteria for Preloaded Bolts (NASA standard), NSTS-08307A
Screw Thread Standards for Federal Services, FED-STD-H28/20

I can tell you more later when I can get to these at work.

[David Stribling]

"Jeff Finlayson" <finl...@hiwaaay.not> wrote in message
news:113n6mk...@corp.supernews.com...

Jeff,
I did a search on your NASA standard, and found this excellent reference
page
http://euler9.tripod.com/fasteners/

David Stribling

[Brian Whatcott]

On 18 Mar 2005 14:16:06 -0600,
mbar...@atsautomation-dot-com.no-spam.invalid (michaelbarclay) wrote:

>All the information that I can find on recommended threaded fastener
>torques and corresponding clamp loads are based on the proof load of
>the screw, not the material that it is screwed into.
>Where can I find information on the recommended torque of a fastener
>being screwed into a 6061-T6 Al plate? Also the coresponding pull out
>load (i.e. at what load do the threads strip in the aluminum)?
>

Off the top: screwing into aluminum plate does not seem like a great
idea.
I could suppose that a force of 90% of pi D X T X shear strength
of plate per unit area would pull out the fastener
A staked nut on the far side of a plain hole, a steel spring nut over
(thin) plate edge, an externally/internally threaded boss/insert of
stronger material would all be better approaches?

Brian Whatcott Altus, OK

[BobK207]

OP-

Jeff's references are excellent, the only one I would add is
Machinery's Handbook.

Depends on what the actual installation looks like & what it the
service environment;

Depending on the application maybe a coil insert or nutplate might be
indicated.

You could also consider factoring the bolt torque by the ratio of the
bolt material yield to the aluminum yield

There's very little chance of an aluminim plate (of reasonable
thickness) fully developing a steel bolt of any kind of strength.

cheers
Bob

[BobK207]

check these out

http://www.engineersedge.com/thread_strength/thread_minimum_length_engagement_fed-std-h28.htm

http://www.engineersedge.com/fastener_thread_menu.shtml

[BobKat]

A resource I have found particularly useful is Unbrako's engineering guide
(2.17 MB pdf file). It has methods for determining pullout as well as high
temperature fastener analysis.
Find it here.
http://www.spstech.com/unbrako/htm/unbrakodl.html
BobKat

"michaelbarclay" <mbar...@atsautomation-dot-com.no-spam.invalid> wrote in
message news:423b3...@127.0.0.1...

[Jeff Finlayson]

David Stribling wrote:

Thanks, I'm aware of that one. It's available on NASA sites too.
The Fed-Std was the main one I need to look at.

[BobK207]

Jeff-

Is there an free online source for FED-STD-28?

I have an electronic copy of MIL-HDBK-5 & a bunch of others but I could
find FED-STD-28.

cheers
Bob

[Jeff Finlayson]

Jeff Finlayson wrote:
> michael barclay wrote:

>> All the information that I can find on recommended threaded fastener
>> torques and corresponding clamp loads are based on the proof load of
>> the screw, not the material that it is screwed into.
>
>> Where can I find information on the recommended torque of a fastener
>> being screwed into a 6061-T6 Al plate? Also the coresponding pull out
>> load (i.e. at what load do the threads strip in the aluminum)?
>
> You should be using an insert. But since you aren't..
>
> The thread shear strength is a function of part thickness, ie number
> of threads carrying load.
>
> You need to perform a preloaded bolted joint analysis. Calculate
> the preload and combine with external loads.
>

> Some references: [corrected 3/21]

> Mechanical Engineering Design by Shighley

> An Introduction to the Design and Behavior of Bolted Joints by Bickford

> Criteria for Preloaded Bolts (NASA standard), NSTS-08307A

> Screw Thread Standards for Federal Services, FED-STD-H28/2B

OK from the Screw Thread standard, the simplified shear area is

As = pi*Dp*Le*(3/4) (for internal threads only)

where,
Le = engagement length = (5/9)*(Dt^2/Dm)*(Ftu-ext/Ftu-int) [simplified]
Dp = pitch diameter
Dt = tensile diameter = (D - 0.9743/n)
Dm = minor diameter = (D - 1.299/n)
D = major diameter (nominal bolt size)
n = bolt's number of threads per inch
Ftu-ext = ultimate tensile strength of external threads (bolt)
Ftu-int = ultimate tensile strength of internal threads (aluminum part)

Basically if the aluminum part's thickness is equal or greater than
the bolt diameter, use Le = thickness.

The aluminum's shear strength capability can be found by

Ps = As*Fsu (shear area times aluminum shear strength)

[kevinjc...@gmail.com]

I'm just gonna put this here for someone in the future.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170003491.pdf

Your welcome 😉👌