Turning titanium?
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Turning titanium?
I’ve got some aftermarket titanium self-extracting crank bolts. The “shoulder” of the bolts is just a little too big in diameter (so the “dust caps” don’t screw all the way in).
Does anyone have any suggestions on how to turn the shoulders down to the original DA 7700 spec? Something I could do at home without a lathe? Should I try and find a machine shop who can do the work? Thanks!
Does anyone have any suggestions on how to turn the shoulders down to the original DA 7700 spec? Something I could do at home without a lathe? Should I try and find a machine shop who can do the work? Thanks!
#2
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File?
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#4
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Chuck the bolt in an electric drill
Clamp the drill in a vise..
Use a decent quality file. You may have to experiment with different cuts.
Clamp the drill in a vise..
Use a decent quality file. You may have to experiment with different cuts.
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It’s an M15 size bolt, so won’t fit in my drill, but my 8mm socket fits. I may give it a try. Have to remove 1.4 mm total diameter.
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1.4mm means 0.7mkm "all the way around.
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If I understand you correctly…. The bolts fit the threaded diameter of the crank, and are not to big to fasten the crank completely to the BB; no issues with properly attaching the crank.
But the shoulder diameter of the bolt, that holds the crank on the BB, is to large a diameter for the dust covers to completely thread onto the crank arm.
And the solution is to remove some of the material from the bolt that is holding the crank on.
Just wanted to understand the situation.
John
But the shoulder diameter of the bolt, that holds the crank on the BB, is to large a diameter for the dust covers to completely thread onto the crank arm.
And the solution is to remove some of the material from the bolt that is holding the crank on.
Just wanted to understand the situation.
John
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If I understand you correctly…. The bolts fit the threaded diameter of the crank, and are not to big to fasten the crank completely to the BB; no issues with properly attaching the crank.
But the shoulder diameter of the bolt, that holds the crank on the BB, is to large a diameter for the dust covers to completely thread onto the crank arm.
And the solution is to remove some of the material from the bolt that is holding the crank on.
Just wanted to understand the situation.
John
But the shoulder diameter of the bolt, that holds the crank on the BB, is to large a diameter for the dust covers to completely thread onto the crank arm.
And the solution is to remove some of the material from the bolt that is holding the crank on.
Just wanted to understand the situation.
John
Last edited by smd4; 04-28-22 at 07:48 PM.
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I've just never used them. I remove them, use a Park crank puller, and then thread the extractors back in as dust (thread) covers.
My question was whether reducing the shoulder on the bolt holding the crank, just to use the extractors, is a good idea. I could be wrong, but to get a nice look, I would reduce the extractor depth and use a crank puller to remove the crank when necessary; which probably isn't very often.
John
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My question is why you want Titanium crank arm extractors? Titanium, in general, is a poor material for fastening type applications though though overall the Titanium 64 alloy has good strength. Certainly, any weight savings is inconsequential. Just my opinion.
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I'm familiar with crank extraction devices that thread in and then removing the bolt pulls the crank.
I've just never used them. I remove them, use a Park crank puller, and then thread the extractors back in as dust (thread) covers.
My question was whether reducing the shoulder on the bolt holding the crank, just to use the extractors, is a good idea. I could be wrong, but to get a nice look, I would reduce the extractor depth and use a crank puller to remove the crank when necessary; which probably isn't very often.
John
I've just never used them. I remove them, use a Park crank puller, and then thread the extractors back in as dust (thread) covers.
My question was whether reducing the shoulder on the bolt holding the crank, just to use the extractors, is a good idea. I could be wrong, but to get a nice look, I would reduce the extractor depth and use a crank puller to remove the crank when necessary; which probably isn't very often.
John
But, you are wrong. Reducing the shoulder diameter to the DESIGN SPEC of the original bolts won't be a problem.
Last edited by smd4; 04-29-22 at 06:51 AM.
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Yes, weight savings. A gram saved is a gram earned. I would go aluminum if I could find any. The stress imposed upon the crank arm bolts is minimal. Thanks for your opinion.
Last edited by smd4; 04-29-22 at 07:08 AM.
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Doesn't sound like you understand self-extracting crankarm bolts and how they work. I don't even think you can use a standard crank arm puller (why would I even try? By design it's unnecessary). It's a completely different design.
But, you are wrong. Reducing the shoulder diameter to the DESIGN SPEC of the original bolts won't be a problem.
But, you are wrong. Reducing the shoulder diameter to the DESIGN SPEC of the original bolts won't be a problem.
Basically you are using an allen/hex head crank bolt with a wide shoulder. Torque the bolt and then thread in the dust/extractor cover “all” the way in with a pin spanner. The cover allows access to the crank bolt. When you want to remove the crank, loosen the crank bolt and the force against the extractor cover as the crank bolt is threaded out pulls the crank.
John
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I have cranks with self extracting bolts. Pretty simple design.
Basically you are using an allen/hex head crank bolt with a wide shoulder. Torque the bolt and then thread in the dust/extractor cover “all” the way in with a pin spanner. The cover allows access to the crank bolt. When you want to remove the crank, loosen the crank bolt and the force against the extractor cover as the crank bolt is threaded out pulls the crank.
John
Basically you are using an allen/hex head crank bolt with a wide shoulder. Torque the bolt and then thread in the dust/extractor cover “all” the way in with a pin spanner. The cover allows access to the crank bolt. When you want to remove the crank, loosen the crank bolt and the force against the extractor cover as the crank bolt is threaded out pulls the crank.
John
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I have no clue if reducing the diameter will have any impact or not; and I don’t really care. Self extracting systems are a convenience for an occasional removal, chainring or BB replacement, and removing the cover and the crank bolt and pulling the crank with a Park tool is a minor inconvenience.
Occasionally there are problems where the cover doesn’t hold when pulling the crank and it becomes more of a pain than it is worth, so I just take that out of the equation.
John
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That's the problem--it isn't the correct diameter. Hence my wanting to turn them down.
The crank bolt in this particular system has TWO "main functions." If the shoulder surface is even just 1 mm wider than the hole in the crank arm, it will be enough to do what it needs to do. There is very little if any outward force on the crank arm.
I don't think I would ever consider using a crank removal tool--Park or otherwise. Wouldn't want to booger up the BB spindle--which was not designed to have a crank arm puller forced against it.
...and can be torqued flush against the crank, not too large in diameter to fit, you are removing material that was hopefully designed to hold the crank onto the bottom bracket. While the bolt shoulder is designed to pull the crank, its main function is to hold the crank in place.
I don't think I would ever consider using a crank removal tool--Park or otherwise. Wouldn't want to booger up the BB spindle--which was not designed to have a crank arm puller forced against it.
Last edited by smd4; 04-29-22 at 08:35 AM.
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Thanks Cranky! I'll check these out. Prices aren't bad at all.
EDIT: Just bought the CCP-44 new from Ebay for $16 bucks.
EDIT: Just bought the CCP-44 new from Ebay for $16 bucks.
Last edited by smd4; 04-29-22 at 08:10 AM.
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Crank arms are supposed to be torqued at arround 35 to 40 nm, which is not insubstantial, my guess is that is why you don't find aluminum crank bolts
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There were aluminum crank bolts, as smd4 noted. The general recommendation was to use steel bolts to apply full torque and then substitute the aluminum bolts as replacement. More than one aluminum bolt was broken by not following this procedure.
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