Replacing the cassette on a vintage bike

My wife and me have completed a few Eroica rides on unmodified vintage racing bikes. By unmodified I mean that the bikes still had the original rear cassettes, which are really meant for racing on mostly flat asphalt roads. The biggest sprocket would be a 23 or a 26. This makes it almost impossible to climb some the steep Eroica white roads ('strade bianche').

Strade bianche uphill on the Eroica Montalcino course

After doing the medium route of the Eroica Montalcino in 2017 (2000m elevation on a 100km course) I decided to modify our Eroica bikes so that we would be better prepared for the next Eroica rides.

Replacing the cassette on  the Koga-Miyata Gent's Racer 1984

The original cassette on this bike was a Shimano Uniglide with 7 sprockets (23-21-19-17-15-14-13). The sprockets seem to be made out of titanium, which might actually be the case for a Dura Ace series.

At first I could not understand how to disassemble this cassette, but I found this very useful video that explains how to go about it. If you prefer text, try this page on the well known Sheldon Brown web site.  You need 2 chain whips to perform this operation.  If you are lucky, you own one yourself, and you can borrow a second one from your neighbor.  If you cannot get your hands on 2 chain whips, you might try the procedure explained on this page.  I used 2 chain whips, and it worked fine.

Shimano Uniglide with 7-sprockets. There is no lockring with notches.

The smallest sprocket (13) is threaded, you can unscrew it using one chain whip.
You need a second chain whip around the largest sprocket (23) to stop it from rotating.

The smallest sprocket has been removed

All sprockets have been removed. Notice the thread on the top of the hub.
Good news is that this hub is compatible with Hyperglide, one of the notches is wider.

I my collection of spare parts (collected over many years from parts discarded by bike shops) I found a Shimano Hyperglide cassette with 6 sprockets: 32-28-24-21-18-15.  This cassette fits perfectly on the Uniglide/Hyperglide compatible hub. I screwed the original 13 sprocket to the hub, using a chain whip.

Replacement Hyperglide cassette

New cassette composed of the replacement Hyperglide cassette and the smallest sprocket (13) from the original cassette

After fitting the wheel back on the bicycle, a small adjustment of the screws that control min and max position of the rear derailleur was necessary.

Koga-Miyata Gent's Racer (1984) with the new cassette: 32-28-24-21-18-15-13.