7 speed to single speed freewheel conversion
 

Some may have noted in my other threads, that I have an old Schwinn Varsity that I'm trying to turn into a budget commuter. One option that I'm looking at is converting it to a single speed.

I found some information on how you can convert a Shimano (and some other) freewheels into single speeds using spacers to replace the unused cogs. Anyone ever done this or see any reason it shouldn't work? I like the idea of having a selection of cogs and being able to fine tune the chain line by moving spacers.

It's a tad more tricky on a freewheel, as they are more resistant to disassembly than cassettes.
Also, the inner diameter of the f/w sprockets are different - not only when compared to a cassette, but also between inner and outer sprockets. And I've never seen a spacer kit for f/w for sale. You'll probably either have to make them, or scrounge a few scrapped f/w for parts. And even then you won't be able to use any sprocket in any position.

What you read has to do with cassettes, not freewheels. For a freewheel, you just buy a single speed freewheel and swap it out. Then you have to redish the wheel. Google single speed freewheel conversion, there will be an endless amount of info out there.

If your lucky you should be able to buy a 16 tooth or larger bmx freewheel and thread it on where the stock scwhinn freewheel threaded on the rear wheel. Chain line should be fine if you use the smaller chainring upfront but im not sure if that would give you the gearing you want or not.

+1, take the original 5 speed freewheel hub , wheel ...
re center the hub , keep the solid axle.
with a few different axle spacers
loosening the right side spokes, tightening the left.

you may need to change the front chainring setup to get the gear ratio size
that suits where you ride.