Bolt and nut made of aluminum 3

[eli28]

Hello everyone
I have to decrease weight in my assembly.
One of the suggestions is using aluminum bolts rather than using low-medium carbon steel.
I checked if it's possible when considering strength, and it's indeed possible if I increase the bolt's size (and I still lose weight).
The point is that I have no experience with aluminum fasteners (bolt, nut and washer).
Does anyone have some tips?
How can I deal with the risk of cold welding of both aluminum bolt and nut?
Which familiar manufacturer can provide me with such of the shelf 10-32 aluminum bolt?

Thabks!

 

[Tmoose]

Drilled / hollow steel screws with dished heads might be of benefit unless COTS is a requirement.

Sometimes smaller, stronger screws are worth considering unless the benefit of redundancy is of little consequence, in which case fewer screws might be considered.

 

[rb1957]

"I am still not sure about titanium seizure risk." This is standard process ... see the Hi-Lok/Hi-Lite website. Procedures to use Ti fasteners are well understood.

another day in paradise, or is paradise one day closer ?

 

[DAVIDSTECKER]

A good coat of Anti-seize should be all you need.
We used it successfully on aluminium NPT pipe for a hydraulic system that pipe dope and taped were failing.
Currently we use it on 316 SSTL fasteners and have not had many more screws lock up.

 

[Sparweb]

to the OP:
I hope you can see through the poor advice given by some people in this thread. All I can do is apologize. Many do not realize that there are different standards in different industries.
Perhaps you already know this very well:
[ul]
[li]DO NOT put anti-seize goop on HI-LOKS.[/li]
[li]DO NOT EVER put unspecified sealants or lubricants in contact with titanium.[/li]
[/ul]The manufacturer will provide you with their installation procedures when you purchase. Use the tools and materials they specify.

to the others trying to answer:
This is like the helicopter control training demo with the ball rolling on a curved surface - it keeps rolling off and actually is worse if you react too quickly.
Titanium is not stainless steel.
If you have never used a fastener that is designed by a fastener manufacturer to be installed according to a set procedure, then you might be surprised to learn that aerospace fastener manufacturers are VERY particular about how their fasteners are installed. They are not sold by the pound and the installation manuals are thick and specific. They don't do well with "auto garage" methods. Since the OP has marked (Aerospace) as their discipline, I'm answering according to aerospace industry practices.

Articles? Whatever... do it right. NASA RP-1228 Fastener Manual

 

[eli28]

Hey Sparweb and thank you for being care and giving advices. Is there a guide/article etc. that lists which compounds/lubricants contact with titanium is forbidden (and perhaps learning why and what are the risks of using these materials)?
I have some manufactured titanium parts with internal threads that we consider using VC3 for preventing bolt loosening. I will be happy to know if it's problematic.
Thanks!!!

 

[mfgenggear]

eli28 (Aerospace)(OP)10 May 21 05:42
This is for a carried device by an aircraft
what does this mean, an accessary inside the aircraft and how critical are the stresses, is it life flight critical. what would happen if the fastener crack.

 

[Sparweb]

Hello Eli,
Titanium is susceptible to hydrogen embrittlement and cadmium embrittlement. Given that cadmium is used in many coatings and corrosion protective compounds, and different solvents have different effects on coatings and plating, you need to know what you are using to do it safely.

MIL−L−46010 / MIL−PRF−46010 is recommended by the aircraft OEM that I'm most familiar with.

More can be found on Eng-tips about this:

https://www.eng-tips.com/viewthread.cfm?qid=332583

This is what makes aviation fun, isn't it?
Here's more fun stuff:

CAUTION: DO NOT USE CHLORINATED SOLVENTS TO CLEAN TITANIUM.
USE SLOVENTS LIKE METHYL ETHYL KETONE (MEK) OR OTHER
APPROVED SOLVENTS{}. CHLORINATED
SOLVENTS SUCH AS TRICHLOROETHANE WILL CAUSE
HYDROGEN EMBRITTLEMENT ON TITANIUM SURFACES.

CAUTION: DO NOT USE CADMIUM−PLATED TOOLS TO MAKE TITANIUM PARTS
WHEN THE TEMPERATURE IS MORE THAN 450 °F (232 °C). CADMIUM CAN
CAUSE A LARGE DECREASE IN STRENGTH IN THE TITANIUM PARTS.

CAUTION: MAKE SURE THAT TITANIUM PARTS DO NOT TOUCH LEAD OR
ZINC ALLOYS. IF YOU DO NOT DO THIS, YOU CAN CAUSE
CONTAMINATION DAMAGE TO THE PARTS SURFACES.

 

[3DDave]

Slovents are always a problem.

 

[eli28]

Thank you Sparweb, very useful information!

 

[Sparweb]

If you are already in contact with an aerospace fastener manufacturer like LISI, then you should have access to more information, and more specific recommendations, for safe titanium bolt installation.
Of course, we can circle back to the original question, and as others observed, reducing weight in the fasteners is a false saving, since they usually form only a small fraction of the structural weight, the alternatives cost more. You can rob money from a weight reduction program by spending it on costly fasteners.