We tell you everything you need to know about sandpaper – but were afraid to ask.
It’s easy to think that surfaces prepared on jointers and planers are ready for finishing, particularly when working with wood that has a straight grain and a fine, even texture.
But no – surfaces may look and feel quite smooth, though closer inspection almost always reveals the presence of minute grooves, or ripple marks, on the wood’s surface. There are also likely to be areas of tearout. While the marks may be very small, they need to be removed in order to ensure a first-class finish.
Don’t think that machines equipped with segmented (aka helical or spiral) cutterheads do any better – they also produce ripple marks that you will want to remove. The principle here is that machinery (including routers and shapers) are used to dimension your stock, not to prepare surfaces for finishing.