Originally Posted by
RobbieTunes
Just a note on the 5mm clearance. I am restoring a 1985 Raleigh, and simply pulled the R crank arm off. It will not go back on as close to the BB as it was before. I've filed any possible burrs inside the crank arm and on the spindle, and still, I'm about 2-3mm farther out than I want to be. I have no idea why.
[MENTION=108582]RobbieTunes[/MENTION] bear with me and I might have an answer for you.
Short course on BB spindles...
The 1st section covers traditional square taper bottom brackets with cups and loose or caged ball bearings.
The highest quality BB spindles were made from high quality alloy steel or bearing steel.
They were fully machined from bar stock in an unhardened condition to near finished dimensions. The shape of the bearing races and the 2° tapers were cut on both ends. Bolt holes or through holes were drilled and the threads were tapped. The 2° tapered flats were machined in another operation.
The spindles were then heat treated to a high temperature and quenched to either through harden or deep harden them, depending on the type pf steel. The spindles were hardened to about 60 Rc. (Rc stands for the Rockwell C Scale which is a measure of hardness - for example, hand files are about 55 Rc, metal cutting tools like drills taps and so on are 60 to 68 Rc)
The last steps were to precision grind the bearing races to size (which can leave a polished finish). The flats were finish ground too.
Campagnolo Record, Nuovo Record, steel Super Record, C-Record, Chorus and some of the others were made this way.
Suntour G1 top quality Spindle ???
A few other companies produced BB spindles with the same quality.
The flats of many BB spindles were not finish ground after hardening which could leave a rough surface that can cause the soft aluminum to gall on tapers and the arms may not seat properly.
[MENTION=108582]RobbieTunes[/MENTION] this may be your problem...
Check out the cutter feed lines on these tapers.
Avocet/Ofmega spindle
Lower quality Suntour Spindle
Stronglight from the 1950's
Later Stronglight 118 Spindle
TA 344 Spindle
Some other methods used to form the basic spindle shape are:
Hot drop forged blanks - this leave separation lines from the forging dies in the mid section.
Hot roll forging reduces the amount of machining. The complete rough shape including the tapers and flats can be done in one operation.
Roll forged Stronglight spindle for lower priced cranks like the TS, 100, 200, 104 etc.
Continued in next message....
verktyg
Chas.