easyupbug 

Titanium workability varies with the grade, while low grades would file easily your crank bolts should be at least Grade 9 which will be hard on the file but work much like high strength steel.

jccaclimber

1. I have a feeling many here haven’t spent much time filing anything harder than aluminum.
2. If you’re half competent with a file, and have a half decent file in reasonable condition, this is a sub 10 minute task for the pair.
3. The big question is how you’re going to hang on to it. A bench vise would be decent, though installing it into the spindle with no crank arm and using care not to carve up your frame’s BB shell would likely do just fine. You can slip the crank arm on the opposite side to stop spindle rotation.
4. Off topic, but I rather like self extracting crank arms. It takes less time, and while I’ve seen a couple strip with a worn tool, I’ve not seen any strip with an already installed self extracting bolt. They don’t look quite as nice as a nice flush dust cover IMO, but we’re really getting into the weeds at this point.

squirtdad

interestingly enough, that is the same thing Rene Herse recommend for their titanium bolts

TiHabanero

I agree with Rene Here. Use a steel bolt to bring into spec, then replace with the ti bolt. Precautionary measure to avoid breaking a ti bolt in the spindle. Makes sense to me as removing a broken ti bolt may prove to be a less than pleasant experience.

70sSanO

That makes sense. Rene site also suggests 25nm for the titanium bolt. It does look like a square taper replacement, but I think the torque ranges overlap some.

John

smd4

Took about 40 minutes for one with a new file. FYI...Titanium is HARD!!
Put the 7MM torque wrench socket into the drill, put the bolt onto the Allen head, held it in my lap and put the file up to it while watching The Office. Kept measuring with the dust cap and a caliper.
I too prefer the flush dust caps of older Dura Ace, but racing teams back in the day didn't even use them, so the Octalink setup doesn't look to bad to me. I like the no-nonsense functional look.

Thanks for everyone's suggestions--it takes time, but is doable.

jccaclimber

Hopefully you were moving the file across the part quite a bit, if not, that’s part of why it took so long. I’m glad you were successful.

smd4

Yes, I was moving the file as much as I could. Wasn't the ideal situation, but again, doable. and got the job done.

WizardOfBoz

And also to machine. Cost factor of 6 over (easily machineable) leaded steel. Requires sharp, coated carbide tools. Easy to build up heat in the turned part. You sure you want to get into this? Probably the tooling would cost you more than just buying new Ti fasteners that fit.

Why is titanium so hard to machine?

WizardOfBoz

Agree - if the bolts are Grade 2 (pretty pure Ti) then machining could be easier than Grade 5 (which has 6% aluminum and 4% vanadium and hence is called 6Al-4V). But unless you have an X-ray Fluorimeter handy you might not know.

If you have a good, rigid lathe and excellent work-holding tooling I guess you could give it a try. For my money, though, I'd just buy properly sized bolts!

smd4

The job’s done, both bolts. C’mon!! It wasn’t THAT difficult! A lathe? Tooling?? A new file cost me $6 bucks from Lowe’s. I used my drill as a “lathe.” The only Ti bolts for this particular application are the ones I bought.

70sSanO

I would guess that since the title used the word turning that is inherently done on a lathe.

My Dad had a metal lathe when we were growing up. Great fun. That said, I have use both a drill and even a bike crank to “turn” something, but it is only a primitive operation with little ability to hold any tolerances.

John

jccaclimber

I guess all the titanium hardware and rod that I’ve worked on a lathe with freehand ground HSS tools and worked with a low price hand file (I have better now) must be an anomaly.
Industrially competitive is hard and has overhead. By hand for qty<10 doesn’t need to be complicated as the OP has shown.

smd4

The titanium bolts I turned without a lathe on a hand drill are well within the tolerances required. I wasn’t building a surgical instrument.

pdlamb

Have to wonder about the self-extracting bolt application, though. It would seem that you'd be loading the bolt both during installation and removal of the crank, and just asking for galling both ways. Be sure to use anti-sieze!

smd4

I used plenty of anti-sneeze.

WizardOfBoz

Glad you were able to do it.
I agree with you that if the large shoulder was just poor manufacturing quality control, reducing the diameter to the design spec is fine.
And others have mentioned that Ti is horrible for galling but you are using anti-sieze.
Regarding the lathe, well, I grew up working in a machine shop and while the tool and die makers might use a "get 'er done" approach, they were so good that they'd probably figure out a workholding solution on the lathe and have that 0.7mm off while maintaining concentricity and leaving a good finish. In about five minutes. So my prejudice for the lathe option.
But if it works, cool.

smd4

Let’s put it this way: I wish I had a lathe!