I assume by "a plating machine" you mean a dc power supply (or rectifier as it is called).
I know a lot of you try the "cheapo" let's try and save a buck method of getting the juice to do you plating, however, using a "real" power supply makes life so much easier and more efficient.
Go to Caswell's site below:
http://www.caswellplating.com/kits/rect.htm
The 3 amp constant voltage/current model will work for smaller items and the price is just frigging fantastic!
The 20 amp constant voltage/current model would be all you would ever need unless you were getting into chrome plating over 20 square inches in coverage.
I have a power supply similar to the 20 amp (mentioned above) except it is a 10 amp supply (Instek brand---looks identical in appearance to Caswell's 20amp supply) and I paid $350.00 for it (2) years ago.
Wish Caswell would have had the 20 amp unit when I bought mine!
You just can't beat the price on Caswell's 20 amp unit.
For $300.00 it is a great deal.
Additionally, either of the constant voltage/current models Caswell sells will allow you to get ultra precision control over the plating.
Spend the bucks on Caswell's units....you will be glad you did!
GW