Using Titanium screws

[freebutterflyx]

I bought some titanium screws. I got them from a friend who bought M3 but needed M4.
My question is: can i use them for all connections (alu-plastic, plastic-plastic, alu-alu,...) or are there places where i can't use them?
ans what are the advantages and disadvantages?

[racer234]

I haven't had any experience with titanium screws, but I can tell you what I've heard. They're lighter and stronger than steel. I've heard that titanium and aluminum can form a "cold weld". That's where the metals bond together if left together for too long. Now I'm not sure how serious this is, but I'd look into it if I were you. I think that if you put grease on the screw before it goes into the aluminum it will ford a protective layer so they won't bond together.

[TRF Drive Hard]

Never heard of that before... cold weld... i been using ti screws in all my high-end kits... i believe if overtightened on aluminum it will bond... but so far i havent had probs... ti is lighter than stock steel, about 3-4 times lighter... also same strength as stock steel... ;)

[DaFF]

Sorry, but that is overly exagerated.

Ti is not 3-4 times lighter than steel.

FYI, steel density is 0.284 Lb/inch3 while Ti is 0.163 lb/inch3

It translate into Ti being 1.74 times lighter than steel.

As for the strenght of Ti against the strenght of the steel, it all depends what type steel you are comparing Ti against.

There are for a fact high strenght steel that can exceed the strenght of Ti.

I don't want to be too technical ( I am a tech aeronautic engineer... ) but Ti strenght properties ( depending on exact type of Ti, but generaly speaking ) has a shear modulus of 6000 ksi and a modulus of elasticity of 16000 ksi.

A high strenght steel like 4140 has a shear modulus of 11600 ksi and a modulus of elasticity of 29700 ksi.

That being said, it is well know that Ti weight to strenght ratio still got the node over any steel and that is the reason why Ti is a material of choice when it comes to building plane or having screws that are strong, yet light.

Though I would clarified that.

BTW, carbon steel and stainless steel will corode when put together, it is a chemical reaction called electrolyt coupling ( or galvanic corrosion ) and because of that, it is recommended to avoid sst fastener on high carbon steel.

But Ti with alum is no problem, we have a lot of fastener in Ti that holds alum plate on planes !

DFF

[TRF Drive Hard]

FYI, i wasnt exaggerating... i only know what i know... but since you clarified the properties of Ti... thank u much... ;)

[microrcdude]

titanium is only half the weight of steel.

[InspGadgt]

In RC Car applications often the steel screws are stronger then the titanium. I've often had titanium screws snap where the steel ones would only bend so for high stress areas I still use steel.

[DaFF]

FYI, i wasnt exaggerating... i only know what i know... but since you clarified the properties of Ti... thank u much... ;)

Sorry if I offended you, I should have use another word than "exaggerating".

Anyway, if you have anymore question about material, feel free toask, I'll be glad to help you - not that I know everything, only is it part of my job to know a few thing about high exotic material ! -

DFF

[TRF Drive Hard]

Blah, i wasnt offended in anyway... just glad that, in the professional field you are in, helped me understand more... actually im interested in those kinds of things... im somewhat a "science nerd" but i like those things... :D

[BCSavage]

isn't Ti more brittle as well and shouldn't be used in high-stress areas due to having heads snap off?

[TRF Drive Hard]

Correct me if im wrong DaFF... Ti in its natural form is brittle... thats why it is mixed with an alloy to strenghten it... :D :p DaFF, help!!! lol :p

[freebutterflyx]

And what about stripping the head of the screws? Compared to steel screws?

[Cotharyus]

Actually birttle implies that it's very rigid and easy to break, that it has no give. In reality, aluminum is much more "brittle" than Ti, and even steel is more brittle than Ti, esp. if improperly hardened. Ti is actually very flexable, which is part of the reason parts from Ti have to be designed so carefully.

As far as stripping the heads of a Ti screw, I would think it would be difficult under normal circumstances. Especially given how hard it is to cut head slots into a good quality Ti screw, but keep that in mind...I said good quality, you need to know what you're picking up.

[freebutterflyx]

The titanium screw I have are from Mugen. So I supose they are designed for RC cars.