Hi Babylon, i'm afraid thats a common problem with Yew and lots of other woods actually, the problem is that the wood is drying and thus shrinking, are you taking the pieces straight into a heated home after you've done them, if so this will exaggerate the problem, ideally the piece needs to dry very slowly, this i'm afraid takes time, hence the idea of roughing out bowls etc. Turn something oversize, then store it until the moisture has balanced out with enviroment, then re-turn piece, on a finished piece straight off the lathe, one suggestion would be to weigh the pieces individually, and then place in a paper bag with the weight and date on the bag, place low down in the workshop and weigh perhaps weekly, when the weight has dropped and no further difference is found from one week to the next, then it has dried out to the same moisture content as the atmosphere. You can move it higher up in your workshop after a few weeks, and once you take the piece indoors put low down again in a cool place and let it acclimatize to your home. Its a bit of a chore, but in time you get to know how long things take approximately and can plan ahead. There are other ways such as microwaving the wood, boiling the wood, etc and sure you'll get several more ideas on here soon. Good luck.
regards Darren
