Ok this is bordering on insanity. I did a Sheldon BB upgrade on a 1973 Supercourse, used the original cups and swapped the spindle to a 173MM MTB spindle to go cotterless with a Stronglight 104 crankset.

Everything is fine with the BB itself, and the drive side chainline is perfect. The left side however could come in a bit more, like 6MM.

Has anyone ever tapered a spindle slightly with a dremel to snug it up? I know using a file would take days, being case hardened steel and all. (Not sure if I want to take a file to the inside of the crank arm (cringe).

This is one of those minutia things that just irk you a little. Could it cause tolerance problems and creaking... probably, if you shaved too much (sigh). Versus time spent endless searching for a spindle that would fit a Stronglight married to a British bike, a strange combo. At least I ditched the Mafac Racers, they squealed like a pig...

no experience in this situation, but i advise not to do it. either post wanted in the sales thread, or keep it as an item in the back of your mind when you go to bike swap meets.

Nah, the tolerances are too high to be done by hand. That and 6mm is a lot longer than it looks when it comes to those kinds of angles. Take good measurements of the one you have and go shopping.
Here's a useful database;
https://mountainbikers.hubsystems.com...s/chapter9.pdf

A mechanic I know filed the inside of a crankarm with a small flat file to get it closer to the BB cup. I doubted about that, but it worked OK.

just get a new spindle.

I get the feeling that the left BB cup is sticking out too much - not the spindle - because the OP says he put a 73mm spindle in a Super Course. A Super Course would have a 71mm bottom bracket.

The 73mm conversion only works on the Raleigh Twenty. If I have interpreted this right, the OP needs to find a 71mm 5-series spindle, or a suitable 70mm Italian spindle.

-Kurt

get a 70 mm spindle and us larger bearing, in theory it should put the left side arm closer in and since its a smaller spindle the larger bearing should push the spindle so the chain ring is where it should be, someone tell if im wrong i dont actually know if its 100% correct to do

Not a great idea, there is only one size of ball that will match the race machined into the spindle.

Just get a ldifferent spindle.

i've had a similar question just out of curiosity.
if the problem is simple enough,
for instance: JIS spindle + ISO crank arm, so there needs a few millimeter more to push in,
could we just file not the spindle but the square hole on the arm side—which should be relatively easier than filing the spindle?
totally understand it's not a nice idea. just thought like why not when things don't idealistically work...
i'm sure there's someone who's tried this, no?

I once filed the taper on a Ofmega crank to get it to go on further. It kinda worked ok but any deviation in the taper means it will rotate off center.

you're so right. didn't think it will become off center...
hmmm.

in fact, i'm having to match a suntour sprint spindle to a campy SR arms.
first it had been to match to an ofmega crank that was sold after learning that old ofmega had an obsolete spindle size. apparently that ofmega was an ISO size, comparing to the campy i got as a replacement. still need to push the spindle in like another 5 - 6 mm.
really love the NOS suntour sprint spindle and want to make it work not having to look for another campy spindle or so...
it does seem ok to screw the bolt in with that 5mm gap—as mr.brown has once said ok too in his article, but you know...

If one had a crank arm that was butchered, say from wobbling by a dazed rider with no sense and the tapered region was hacked, then and only then would I attempt a re-file of the taper. Pretty dire circumstances. Taking of equal amounts from four sides is possible by hand, but one would have to really as ONE with the file.

Digging into the spindle beyond the hardened region... I would only with a mill and a set up, then knowing that the remaining spindle is short changed.

In short, measure what you have and go spindle hunting. My first stop would be the oldest local bike shop in town that was adult bike oriented in the past. And take a caliper. Marginal shops are still dropping like flies here, many with no external notice, just one day- poof, gone. A bummer, but one guy walking into a smoke filled shop buying oddball parts on a routine basis is not a business plan.

I walked into another local shop last weekend, an immigrant couple bought the business from the previous owner who found out that an independent bike shop was a high work, low income life. Nice couple, I bought $20 worth of stuff before my children requested we GO. It was right before Christmas, the place should have been hopping... maybe I should leave my card for the asset sale.

It's a press fit........with dissimilar metals.......in a high torque location.

My advice would be to reexamine your own assumptions with regard to
what you are and are not capable of doing with a dremel or a file.

Then either be happy with your results or keep looking for the correct
spindle. They can be difficult to come up with. Look for a nearby coop
or other boneyard and look at the crapped out MTB's with tapered spindle
BB's. At one time they were all over the place, now not so much.

Tapering a spindle, without proper milling equipment, is not a good idea. As suggested by others, get a proper spindle.

Only God and one other guy can make a file go perfectly flat and true. That's why they invented machines.

6 mm is a huge adlustment. If it's case hardened, you'll be eliminating that layer, attaching your crank to te softer core metal. If it's through hardened, you'll probably wear out a box of files. Get the right size of BB.

Why do this? Campy spindles are not that hard to find.

What size spindle and taper do you need, I have a few kicking around?

Filing the spindle would be an even bigger mistake than ditching the MAFAC Racers.

"A Stronglight married to a British bike" is not a "strange combo" at all.

+1, get the correct spindle. It virtually impossible to achieve the necessary accuracy with the described manual process. Besides, once it was done, you could not tighten the crankarm sufficiently, as the spindle end would be protruding beyond the end of the tapered hole. You'd have to cut several millimetres off the end of the spindle and probably tap some more threads into the spindle hole. If it's a Maxy spindle style with protruding studs, it's even more work.

Stronglight spindle for the 104 crank is 118mm. Look at my avatar picture. It's a 104 on my '78 Raleigh Pro.

Problem I ran into: I couldn't locate English threaded Stronglight cups. And Campy BB spindles were too short. So - could I mate my Campy cups to my spindle? Nope - the Campy cups (along with a Sakae and something else I tried) were too thick and my left cup stuck out too far. So I located some thin Victory cups and all was well. Now my problem may be your solution. I was working with a 68mm shell. Kurt indicates you have a 71mm shell. Campy Record/ rifled-thick cups plus a 118mm Stronglight spindle may be your answer.

And you can preassemble these mixes off the bike and use calipers to measure the resulting BB external widths.

Off center. Crank arms not parallel. Tapers not fully engaged. Chances are those of us who are not mechanical engineers will miss a lot of things we should have thought about. That is why you get a new spindle. Of course...

You might get lucky, and things will work out just right. Or, you might find out, twenty miles away from home, the one, or both of the crank arms loosened off, rounding out the taper fits, there-by destroying the cranks. Which, of course, means that you get to walk home, buy the spindle and a new cranks set.

Good luck and keep us posted.

A really good Campy resource, Bicycle Classics (www.bicycleclassics.com) seems to be back up and running after being MIA for a while. On their Bottom Brackets page, at the bottom they have a Reference Table for Campy spindle and cup selection that is thought to be reliable for SR and NR cranksets.

He says NR and SR arms are identical in spindle fit. So the NR selections are applicalble for your crank as long as it's not really a Gran Sport ("GS" imprinted on it). So you need to look at this page, find your situation (crankset age, track/double/triple, BB shell width, BB shell threading, thick/thin cup) and find the spindle specs, then look at the available part lisitngs to see the imprints on the spindle. Don't worry about the prices, this seller specialized in mint, boxed, pristine NOS. But having learned what you need, you can search for the correct part NOS.

BTW, I have an Avocet crank which wants an Ofmega spindle (Avocet re-branded an Ofmega crankset). I might be interested in the one you have. It's obsolete, but I might be able to use it.

I have a 117 Nervar spindle, cups and bearings that might work others may comment on this.........

Thanks guys, that's pretty much what I expected to hear. I can "live with it" for now. capecodder, let me see what I can do. This bike is not a grail-bike anyway. I forgot about the Italian taper thing, thanks for reminding me.