Hi Richard

​Just looking at my SM-9, it has two springs, one either side. Now, it's been quite a few years since I left England, so I'm not at all sure what the iron mongers stores are like today, but here's what I would try first. Take the existing spring off your machine and head down to your local Halfords, Dobson's or DIY store, or what ever store you like to frequent and ask them if they can match up a pair of springs.

Over here in Canada, springs are usually sold in packages of 2, so you get a matched pair. Install both springs and see how your machine behaves. If you can't find an almost exact match, get a pair of springs that are slightly longer so you can cut a few coils off the end and bend the last coil up to form a new hook. The stronger the spring, the harder the machine will be to shift, but you'll have a more positive lower case stop. As Uwe says though, the best would be to find a spring or a pair of springs from a donor SM-8 that's being cannibalized or scrapped out, then you'd know the spring would be factory original specifications.

Best of luck with your venture, and a happy new year to you,

​Sky
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