One of the biggest mistakes I have noticed through the years is the misunderstanding of two different metals forced to be together. Take the tapered cranks for instance. The correct torque used on the first assembly is a big deal. I have been restoring bicycle for many year now there is a big difference between a parts changer and a mechanic.
On new alloy cranks to a steel tapper spindle it is paramount you do it correct the first time. make sure you free ball to get that 50 to 75 years of use out of it.
well any way the aluminum cranks stretch when placing them on and this is what they are suppose to do. And blue loc-tite is a must. I never lubricate the tapper.
You want the electrolysis to happen. That is aluminum oxide and it will swell the crank and actually make a better fit.
remember we are building this for customers and want them to last. if it is hard getting them off 10 years down the road take the bolt off hit it with oil. wait a day and then little heat with a torch and it will walk off.
The main reason used crank installations fail is from the mechanic not letting the metal go back to shape. And the mechanic not marking the crank arm and spindle.
Remember it has changed the moment you put 500 pounds of muscle pushing down on it.
I like to put my cranks in the freezer. Yes in the freezer and my spindle.this makes my aluminum stiffer and it makes my spindle smaller. "Or wait 8 hours" This allows the alloy crank to shrink back.
The fact is that crank is not a virgin and will never be the same. It is up to you to look at it as your putting it on make sure you get at least 26 nm on them. the aluminum will warm up faster than the steel spindle slowly it will all meld together. This has never let me down after learning it from another old time bicycle mechanic.
Trust me you do not want to ruin a old set of TA cranks they are hard to replace. As far as old steel cranks the number one reason is the mechanic did no lube them put them on vibrate them with a drift then re torque them ride it then re torque .
as far as today's truvative or shimano type that use a bolt not a nut. It's the splines on the cartridge bottom bracket get ruined they made them this way sorry guys. I have a old suntour cartage bottom brackets that still going down the road. the threads on the newer cartridge get stressed out. you should run a tap down them clean them up then and new bolts loc-tite.
if you look at the newest cranks sets out today they look like what we had from the 1800's slide through and tighten one side up. yes they like to think it is new. fact is it is easier to assemble.
if you read all this thank you old timer
Flats Fixed.