Yeah, you'd be surprised how many people I've seen giving this advice online. I guess they're worried about the cranks working their way loose and/or couldn't find a torque spec.

And maybe that's why the "do not grease" recommendation got put into several bike maintenance publications. A caution to over-zealous, ham fisted amateur mechanics.

I always use a torque wrench and always tighten to 25-27 ft/lbs.

Dang, first time in my life I ever heard of that. How do you keep track to get it back to the original position? Magic Marker?

And since I'm usually building up a bike with parts from various sources, maybe it doesn't matter anyway...

A couple of tiny adjacent "prick punch" marks on each piece is the norm.

It's pretty much a standard machinery pre-disassembley maneuver.

Tape, magic marker and alike will work, but the chance of losing those references is high.

I was trying to show manufacturing variables, especially between 2 supposedly identical Stronglight spindles.

Up through the late 70s most BB spindles were asymmetrical.The drive side was longer.

One other thing, on used crank arms there is not that much difference between JIS and ISO tapers... Per Sheldon Brown (rip), it fits it works!

I think that I posted some notes with the pictures,

Chas. verktyg

Ah, good advice. Come to think of it, I have seen that on parts before. Thanks!

Yeah. A couple of small indentations, like at the red areas shown here would do it.




Matter of fact, if the components were able to be flipped side to side or end to end, a set of single marks on one and and double marks on the other end would ensure correct orientation and placement.

Present company excepted of course. Don't like to quote myself but thought the above may possibly get misconstrued as a slight against someone on the forum. I'm the only ham-fisted amateur mechanic I know here.

Hmmm...."Clocking"......I thought that term sounded familiar........I used to "clock" my spark plugs (for a whole different reason you might know about) on my cars and motorcycles per recommendations from car/bike gearheads which I confess I was, at one time. Never thought of doing so with a crankset, but I think it makes sense as I agree that bicycle component tolerances weren't the best with many manufacturers in the 70's and 80's

Chombi

And I'm sure that many were assembled with component "sweet spots" factored in for best fit-up. That and maybe "tweaked" just a little to conform to fit.

Gives one a whole new "heads up" when swapping in donor parts too, huh?

I may be over emphasizing the component relationships, but I've been trained on everything from Nuc Submarines to (well) BIKES!

Hey now, I resemble that remark!

I'll have to give it a try, but it wouldn't surprise me if the spindle was as hard as the punch. I know they're pretty hard, at least in the bearing race regions.

The ones I've seen are not, at least on the ends as pictured. There IS always the magic marker indication with a careful resolve to not erase them.

You could also take the procedure a step further using a Dremel with a stone grinding tool, should hardness prevail. Just a touch-off mark is all that's needed to ID.

Carbide or diamond tipped (vibrating) engraving tools or simply a hand held Machinist scribe with the same type tips, will suffice too!

AND...nail polish works!

Lots of options.

I think you are giving bike assemblers way too much credit.

Sheldon Brown vs. Jobst Brandt: Clash of the Titans.
Brandt is a curmudgeonly wonk, Brown was a maven (I say that with all due respect to both). I'm generally a Brownian, but I take the Brandtian approach to spindle greasing. I really doubt that it matters much either way.

On the subject of grease/no grease, I've heard that up to 80% of the torque you apply to a bolt can go to overcoming friction between the mating surfaces, rather than establishing the right preload. So anything effecting friction could definitely make a big difference. Which is why really important applications use hydraulic or thermal tensioning instead of torque, but of course we generally don't have that kind of equipment in our garages. More than anything, just go on feel, and be gentle. Do not use a lot of force unless you know it is called for.

That has merit with regard to the threaded portion and under head contact surface of the fastener, as any torque needed to overcome resistance can throw off the ultimate bolt torquing spec.

Machinery assembly (engines in particular) use a bolt stretch measuring device, verses straight up torque values for that reason.

The grease or no grease issue is confined the the square tapered portion of the shaft in this bike case. There, I don't think the end result (w/grease or w/o grease) is significant. I wouldn't purposely degrease that surface, nor would I intentionally lube it up, but just clean the area of any debris. WD40 there maybe. Then a little oil on the threads or some anti-seize lube.

A avoid all traces of lube, too, for the same reason. I have never had a problem removing a crank either.

-G

I like to use an anti-seize compound, like Loc-Tite C5A, on both threaded and slip-fit connections, especially between dissimilar metals...like the steel and aluminum alloy of the BB axle and crank arms, to minimize the risk of corrosion/electrolytic galling and seizing. It's essential to clean the mating surfaces before assembly and use a light coating of lubricant/anti-seize compound. If you're careful about torquing you will not overtighten or undertighten the connection. I use C5A on my seatpost and barstem slip joints and have never had to deal with a seized (or loose) joint.

Of course you can have problems if the mating surfaces are sloppy to begin with, but that is another issue.

Lots of superstition and old wives tales here. I've not studied square taper crank spindles in particular but they are a subset of machine assembly in general. Whether it's the square taper or the threads, coefficient of friction plays a major and analogous role in both cases. At the end of the day, with a bolted joint, you want a deterministic axial preload, for the integrity of the joint. In the case of the square taper crank spindle, the bolt preload does two things simultaneously: it indirectly determines the radial preload on the square taper (via the jacking effect of the axial preload on the radial preload), and it ensures that the bolted joint has sufficient axial preload to preclude loosening and backing out of the fastener, due to cyclic stress reversals.
Now the radial preload on the square taper is there for two analogous reasons; one, to pre-load the crank arm in hoop stress so that the added hoop stress due to the jacking effect of applying pedalling force to the crank arms is relatively small, so that the cyclic stress reversal amplitude due to pedalling is relatively small compared to the DC hoop stress, and two (a byproduct of one) the possibility of relative motion between the crank and the spindle is nil, so that fretting and/or loosening will not occur.

Lubrication, per se, is a bit of a side issue. Both the aluminum crankarm, and the fastener, have upper limits of stress that they can withstand without yielding plastically. Typically, in both in a bolted joint, and in this special case of a square taper crank, plastic yielding is bad, but there are definitely exceptions in specially designed bolted joints, and it's possible there are in square taper cranks, though I doubt it.
The thing is, the specified torque, whether a bolted joint or square taper crank, is only valid with the specified lubrication. One without the other is an incomplete formula. The specified lubrication (and prior preparation, e.g. cleaning) determines the coefficient of friction that results in the conversion of torque to axial preload (in the case of the bolted joint), and the conversion of axial preload to hoop stress, in the case of the square taper joint.

So, with the incorrect lubrication or the incorrect torque, the joint is compromised one way or another. Here are the possibilities:

1. too much friction, correct torque - the preloads will be less than designed, which can cause loosening of the bolt or the crank, fretting of the crank, and probably worst of all, increased fatigue damage to the crank due to higher cyclic stress amplitude
2. correct friction, too little torque - same as 1
3. too little friction, correct torque - danger of plastic or complete failure of crank or fastener - may result in early fatigue failure of crank, or make the assembly impossible to tighten properly after being disassembled
4. correct friction, too much torque - same as 3, this is probably what happened to the OP.

Clear as mud? Good... I thought so.

I know this is an old thread, but I have a related question. I bought an old frame that has a BB with a square taper spindle (old DA?). If crank openings become slightly enlarged with each install/uninstall cycle, how much of a gamble is it a to buy any old crank in hopes that its opening isn't too large for the spindle I have?

I have never had an issue with this and have used a lot of old cranks. Sure there is a chance, but I bet you will be fine. I would be more concerned with have the correct spindle length for the crank.

+1

This goes back to elastic v plastic deformation. Proper tightening should result in elastic deformation of parts, where any change in dimension is completely reversed when the part is removed or the bolts de-tensioned. If you go beyond the range of deformation that is elastic, you get irreversible plastic deformation, which actually represents weakening of the crystal structure of the materials, in this case the aluminum of the base of the crank arm. With enough of this over tightening, the crank arm will fracture, possibly during a climb.