Firstly, make sure your swede is fresh. It should be very firm all over without any very soft spots. It's a very tough vegetable so you will need an appropriate knife - ideally a large chefs knife which is very sharp.
First cut off the top and bottom of the swede. This will make it easier to peel as you can rest it cut side down and it won't roll around. You can use either a vegetable peeler or run the knife down the sides, just a couple of millimetres in.
Once peeled, cut the swede in half by placing it cut side down and using your hand to help push the knife through - be very careful. Now place the wide-cut side down on the chopping board and cut into 1 cm slices. You can then cut each slice along the length and then across the width, again around 1 cm in width. This will then give you uniform 1cm chunks.