I have just bought a 5 speed derailleur Brompton..fitted into 120mm dropouts..The hub is a freehub cassette with 5 sprockets..12 to 23.....The freehub cassette has been cut down..spacers have been taken off the non drive side..

But my question is this..how can you cut down a freehub..so that it only takes 5 sprockets..

Some early Shimano Freehubs were 5 speed.

This is a freehub not a screw on freewheel..

Some of the early Shimano free hubs were only 5 speeds and not freewheels but cassettes The other thing is if it is a new bike and you are a manufacturer almost any part can be made for your OEM bike. Roger

I was not referring to a freewheel. A Freehub is a trademarked cassette system.

Don't think older uniglide freehubs were as small as 12t
even Dura Ace freehubs for Race Bikes, in the 80s were 13t top gear cogs

but until the Poster submits pictures It's only going to be a blind guess.

Given Brompton never sold a bike with more than 2 cassette gears.

But people have the ability to make changes, after sale, with home machine shops.

https://www.velobase.com/ViewComponen...m=110&AbsPos=9 for a 5sp freehub. That threaded Uniglide cog size went down to 12t, the smaller Dura-Ace thread went down to 11t but I don't recall whether DA was produced in a 5sp option.