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!

 

[Compositepro]

Titanium.

 

[TugboatEng]

Ditto, at that small of a size the price of titanium should be palatable.

If you do go the aluminum route use a metal free anti-seize compound.

 

[eli28]

Hey,

Do you have a known manufacturer of titanium screw?
Do you have a recommendation to an anti seize compound?

 

[desertfox]

Hi eli28

you can get aluminium or Titanium nuts and bolts here

https://raceboltuk.com/titanium-c4

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[mfgenggear]

aluminum on aluminum will gall unless they are coated. the threads will seize.

 

[eli28]

Do you have any recommendation to a coating that can prevent galling? I have in addition to apply a locking element such as patch.

 

[SWComposites]

Is this for an aircraft? If so, what part?

 

[mfgenggear]

anodize with chemical film is very cost effective then anti seize on threads. I would suggest to run test with elongation of the bolts to get correct torque.
aluminum will strip out very easily and easy to do, titanium if not cost prohibited would be a better choice.

 

[3DDave]

No anodize on fasteners - it is a fatigue crack initiator. Use alodine/chemical conversion coating.

 

[mfgenggear]

3DDave (Aerospace)9 May 21 20:36
No anodize on fasteners - it is a fatigue crack initiator. Use alodine/chemical conversion coating.
Hi Dave
that is news to me I made tons of aircraft parts anodize. do you have a white paper or data to support. I believe you
but engineers have to verify. chem film in it self is very thin and does not do much. why I suggested anodize it gives aluminum a hard
outer plate it is half penetration and half build up. more or less. and there are three types of anodize, I recommend sulfuric or chromic
hard anodize has to much build up.

 

[3DDave]

Described in

https://www.eng-tips.com/viewthread.cfm?qid=381192

and

https://hal.archives-ouvertes.fr/hal-00714350/document

"anodization of wrought 6061-T6 alloy gave rise to an appreciable reduction in fatigue strength (60% debit) and the presence of cracks throughout the film is responsible for this degradation." and other examples.

 

[eli28]

After reading all of your advices I understand that titanium is preferable. I still have 2 uncertainties regarding using titanium:
1. Is there a risk of cold welding when using titanium bolt and titanium nut without any special coating?According to this website, there is a risk of cold welding when using titanium:

https://www.boltdepot.com/fastener-information/materials-and-grades/thread-galling.aspx

2. If there is a risk of cold welding, and a coating such as "Tafgel" is required - how can I use it, if I also have to apply "VC3"(quite like Locktite) which is applied to the thread an hour before assembly and help secure the bolt, so it won't loose in vibrations? How can I combine both coatings, if possible at all?
Thanks

 

[mfgenggear]

Thanks 3Ddave
Eye opener. Very good archive discussion.
I retract my suggestion. Holy moly.

 

[3DDave]

I looked and saw a lot of ads for decorative anodized screws, so I can see where the impression comes from. And I have some dyed rivets, but maybe as they are under different loading than threaded screws it's OK. Or maybe they are also more decorative than high strength. The only aluminum screws (plain/no finish) I've used are wood screws for storm windows. Steel ones rust and stain.

 

[Sparweb]

off the shelf 10-32 aluminum bolt?

Please, everyone just stop talking about aluminum threaded fasteners. There are so many horrible things that haven't even been mentioned yet.

If this really is for an aircraft, I'm begging you... use Hi-Loks LISI

There are alternatives, there are even better kinds than this, but if you're casting about on an internet forum, and the munchkins are entertaining your aluminum notions or leading you around to "cheapboltbin dot com" then you need to get a "good enough for Boeing, Bombardier, and Airbus" kind of answer and move on. Quickly. If this really is for an aircraft, ignore all commercial types of bolts, all the bargain bin bolts, all the online order bolts, all the cheap stuff... just don't do it.

 

[mfgenggear]

The Op was asked if this was for aircraft, never answered.

 

[eli28]

This is for a carried device by an aircraft

 

[rb1957]

yes, agree with Sparweb. There are no weight savings using Al fasteners, only more hurt. Use Ti Hi-Loks or Hi-Lites for a minimal savings.

Fasteners are not the thing I'd try to save weight on, unless I was dealing with thousands/millions of them. I'd poke at the structure, maybe use 7450 instead of 7075.

Of course, once you meet some weight target, someone will say "we need to reduce the cost" !

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

 

[eli28]

Thank you all.
I will use titanium screws rather than Aluminum.
I am still not sure about titanium seizure risk.
Try to figure out through some articles.