Turning titanium?
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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.
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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.
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.
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interestingly enough, that is the same thing Rene Herse recommend for their titanium bolts
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#29
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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.
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John
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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.
Thanks for everyone's suggestions--it takes time, but is doable.
Last edited by smd4; 05-23-22 at 07:17 AM.
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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.
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#34
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Why is titanium so hard to machine?
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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!
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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.
Last edited by smd4; 05-26-22 at 06:31 PM.
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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
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
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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.
Industrially competitive is hard and has overhead. By hand for qty<10 doesn’t need to be complicated as the OP has shown.
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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.
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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!
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I used plenty of anti-sneeze.
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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.
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Let’s put it this way: I wish I had a lathe!