I realize this subject has been done but would like to show an alternative to 240 volt drive .As with everyone else I used what was available in the shed and local dump.I found 3 treadmills and scavenged the motors and heaviest frame from them .There were 3 different power ranges ,1.25 hp , 1,75 hp and the one I used 2.25 hp.
The frame is old step treads and treadmill frame .The motor mounting is a treadmill setup / I tried to use a cam set up for the motion but it was not successful and the revised motor set up was used.
The table top frame is 25mm steel with piano hinges to offer different side slope . Currently it is set to 15 mm .the top is 3mm lamipanel with the slots routed in at 1mm .I only had a square sided bit but this works very well with fine gold and tin .
Sorry out of upload for more pics .
The motors are rated to 180 volts DC .With a speed controller from ebay , i have tried 24 vdc and the speed range is 50 -60% of the voltage . At a pinch a single 12 v battery will power it for over 1 hour .
Additional diagonal side supports have been added to allow the unit to slide .Hope this gives some ideas .

The frame is old step treads and treadmill frame .The motor mounting is a treadmill setup / I tried to use a cam set up for the motion but it was not successful and the revised motor set up was used.

The table top frame is 25mm steel with piano hinges to offer different side slope . Currently it is set to 15 mm .the top is 3mm lamipanel with the slots routed in at 1mm .I only had a square sided bit but this works very well with fine gold and tin .
Sorry out of upload for more pics .
The motors are rated to 180 volts DC .With a speed controller from ebay , i have tried 24 vdc and the speed range is 50 -60% of the voltage . At a pinch a single 12 v battery will power it for over 1 hour .
Additional diagonal side supports have been added to allow the unit to slide .Hope this gives some ideas .