I always think that a big press is failrly straight forward; 10 ton hydraulic jack and a frame work from welded steel or multiple 4x2 Timbers. The scratter is the more difficult thing to make; roller, bearings, chutes, etc etc
Looking on YouTube found one guy who was using a [u:13q3133n]garden shredder [/u:13q3133n]as a scratter. Brill idea! <!-- s:D --><img src="{SMILIES_PATH}/icon_biggrin.gif" alt="

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Only concern would be to check the motor deck won't allow juice to enter the motor. I doubt it can but deoending on the model then it might need a bit of FG silicon
PS: Only use it for juicing apples <!-- s:wink: --><img src="{SMILIES_PATH}/icon_wink.gif" alt="

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Cheers
Will