I'm wanting to replace the Nervar crankset that came with my Sprite with something more modern and lighter and stronger and without those dang cotter pins.

However, the bottom bracket is the wonderful 26tpi Raleigh. How can I upgrade this? Are there new spindles I could buy that'll fit the original cups? Do I have to spend an arm and a leg to go the Phil Woods' route? How expensive is it to retap the threading?

Also, will modern sidepull brakes work with the Raleigh frame? I've got 27" wheels for it so I'm guessing the new brakes will work but wanted to check before I bought some.

This may help:
https://www.sheldonbrown.com/raleigh26.html

I hate cottered cranks. As per Sheldon's site, I upgraded my wife's Raleigh Sport 3 speed to cotterless cranks by using the original cups, loose balls and a Sugino axle. Some axle bearing races won't fit thru the hole in English cups. Suginos just barely did.

Okay, I went to Harris' site and measured my axle but there's no perfect match. Short side is 32, middle is 52, but the long side is ~47mm or so. Overall ~133mm. The long side being the one holding the crank; so I can go with something shorter since I'm just putting a single chainring on the crank. But what length do I choose?

On this chart, most everything is gone forever.

There is a Sugino that's 35mm, 52mm, 37.5mm; part #3S-B that's 124.5mm but everyone else says their 3S-B is 121.5mm.

On another site I've found I found a track axle; the 3NN-B. it's 36mm, 52mm, 36mm. There's also the SG-75 spindle that's also 109mm.

The track spindle seems to be the proper choice; the Sugino RD crankset is what I put on my wife's Peugeot.

CharlesC, which Sugino spindle did you get?