If you're thinking of buying one of ALDI's £5.99 table vices, don't bother. I bought one, and it's total crap. Neither of the threads - for clamping it to a table and opening and closing the jaws - work smoothly. The working part of the vice is connected to the table fitting by means of a ball joint, allowing the orientation to be adjusted. Problem is, said ball and its housing are both made of cast aluminium - with lots of flashing, preventing smooth operation.
I've improved it somewhat by totally dismantling it, fettling off the flashings and then lubricating everything before re-assembling it. Unless you're prepared to do the same, I would recommend avoiding it! Mine is now probably worth six quid after I expended twenty quid's worth of labour on it.