Working with Titanium (6al-4v)

[mod_o_matic]

So, basically going to make bike axles out of grade 5 titanium. I have talked over with a machineist the best way of doing it and of course carbide tooling is going to be used...
What i am not sure about is heat treating. I am pretty sure you can't machine a heat treated part unless your grinding it down to tolerance. Is this correct?
Alsom is there a massive increase in strength after heat treatment in titanium, i have researched but have not found what i need to know...which is, if making a replica axle of a steel heat treated one, when made exactly the same out of titanium would it be the same strength? Would htere need to be heat treatment?

Also, if any one has recomendations on how to machine ti, i would love to hear it.
BTW, all work is going to be done on a lathe. I will try to get pictures of what i am trying to make..

Any help is useful, thanks!

[mod_o_matic]

Can anyone give me pointers?

[tobyaxis]

Slow RPM & Low Feed Rates.

Titanium isn't so bad when you get used to it but it takes time. It is best to try a test part first.

Your application may require buying a Steel Part and Reverse Engineering it.

BTW: Titanium Alloys do work harden when machining.

[Superman]

Bit of an overkill using Ti

Turning Ti should not be a great problem if you
- keep a good supply of coolant
- do not "dwell" the tool in one spot ( work hardens)
- use "sharp edged" tips ( and keep them sharp )
- keep a good, constant feedrate ( not a slow feed )
- entry into the cut is a real killer ( use a gentle lower feedrate at the start of cut, and then increase the rate
- cutting speed for carbide ( start about 45m/min=145 ft/min )

IMHO
Would be cheaper/easier using a case hardening or nitriding steel
( the centre kept softer to give a little flex, and avoid a bad break ?)

[the mill kid]

I have done a lot of turning and milling ti we are running 200 sfpm with a .012 feedrate and a .100 depth of cut on our lathes. Kennametal makes a great ti insert the grade is 5025 or 5525 one is for an interupted cut. Duramill makes a great endmill and it is cheaper than a z carb and we were running that at 200 sfpm 22 ipm with a .375 depth of cut with 50 percent of the endmill engaged and it ran awesome! OSG makes some great carbide drills and taps for ti. I was able to form tap 480 4-40 holes at 25 sfpm in ti with one tap!

[Rich Kay]

One tip I can share with Ti, if you have the capability to flood with coolant do so! If not, have a chemical fire extinguisher right next to your machine! Thin, "balled up" Ti chips can explode and burn if the chips get too hot. (I've seen this occurance FIRST hand)

Ti barstock actually is very easy to turn. Ti castings can be a real challenge. The issue with Ti is it's abrasive resistance, and it's ability to deflect and dissapate heat quickly. Ti is very common where minimum weight, and rigidness is a priority. Good luck!
Rich

[ChristianK]

Never machined heat treated titanium but in my experience titanium isn't quite as strong as heat treated steel. It is light and semi-durable but nowhere near steel.

Machining titanium isn't hard at all. Feeds and speeds are key, keep your tools sharp and machine rigid. WATCH FOR FIRES!

[mod_o_matic]

Thanks for the tips.
I have been told that you can machine heattreaded Ti with carbide, is that correct?
The axle is being replicated from a hardened steel version btw. I was taught not to use coolant with carbide cutters, is there a special case or something?
Thanks for the help!

[diecutter]

Either flood it with a constant heavy stream of coolant or cut completely dry. It's the thermal shock of intermittent coolant that causes micro-fractures in the inserts cutting edge.

[g-codeguy]

Originally Posted by mod_o_matic Thanks for the tips. I have been told that you can machine heattreaded Ti with carbide, is that correct? The axle is being replicated from a hardened steel version btw. I was taught not to use coolant with carbide cutters, is there a special case or something? Thanks for the help!

Depends. How hard will it be on the Rockwell C scale? You can always use ceramics if it is hard enough. However, giving its tendency to light up when hot, you'd better keep it flooded REAL good. We cut hardened steel dry, but I sure wouldn't try that on Titanium.

You should be able to cut the hardened material with carbide inserts, but the SFM will have to be cut. How much depends on how hard it will be.

Never heard that you shouldn't use coolant with carbide cutters. I work for the grandson of the man who started the company where I work. Guess you could say we have been doing it wrong for a long time then.

We don't machine that much Titanium so my experience is limited. Never have machined heat-treated Ti. I do know that I prefer machining some materials that have been heat-treated a bit versus the same material in is soft state.

EDIT: I don't think I would run it completely dry. I've seen fire on a lathe before. Not fun. Can't recall the materials we have had it happen with. Yes it has happened more than once. I know for a fact the last time it wasn't Ti that caught on fire.

[youngjim]

It might be helpful to note that there are cyclists who will strip the paint off their bikes to save a few grams, so titanium axles aren't that wild an idea

Jim

[mod_o_matic]

Oh this is not a wild idea at all. I have always wanted to make some instead of buying them as it is much cheaper =P. Its only since starting a tool and die course in college that now have some basics/tools/resources to do this now.

OSG only has imperial taps, is there any company that makes metric carbide taps for ti? Looked through and good pricing and a very wide selection...

If i have a m14 bolt what would be the best thread for it in a 6mm axle?
Give you and idea. 1'' OD (my stock size) with the said 14mm hole that would be needed...


The bolt currently is a m14 2.0 thread bolt in hardened steel with helicoil. Helicoil is just there for fool proofing it... Is there a better threading i could use to replace it? What is best for Ti, course thread or fine thread? Is a helicoil necessary for ti could i go without it. Any 1/2'' threading i could use?

I will get a more accurate picture with exact dimensions to give you a better idea. I should be getting my stock in a week or so...hopefully get some pics up to when start making it =P

Thanks for the help.