I have wood block of 50 * 50 * 50 mm. I want to make 1mm hole ( depth), having diameter of 40mm. Which power tool should I use?
The best bet for this is to use a drill press so that you can maintain positioning of the block and the drilling tool for an even and square operation. A drill press often also includes a depth stop to help with maintaining a repeatable drill depth if you are producing multiple parts.



The type of drilling bit you want to use for an operation like this would be a Forstner bit. For shallow depth drilling you will want to use the type of bit that looks as follows with the smooth sharp radial cutters.



Avoid the type of bit that has the multi toothed radial cutters as this will not give you as smooth of edge on your shallow depression.



For safety sake make sure to securely clamp the small block of wood to the table of the drill press. One recommendation to make things a lot safer is to drill your shallow depressions into the face of a longer piece of material and then cut it down to size. It is far easier to clamp a larger piece.