I'm pretty sure everyone would rather have the repair enchantment on a tool or piece of armor that is not the less speedy, protective, or durable thaumium material, but by using an anvil or enchanting table you will never be able to get repair on your shiny diamond pick.
However, I have discovered through the use of the Twilight Forest's mod's Uncrafting Table, you can take a once enchanted thaumium tool or piece of armor with repair on it and swap out it's material for diamond.
Shown below is an example. Please forgive me using a hoe as an example, but it was the first tool that got enchanted with repair
Also note that this method can be further used to get Soul Stealer on a repair item and then on a diamond sword. Also do note that enchantment level can get rather high (my pick cost 49 levels). Also this will only work on items that can have their materials replaced.
However, I have discovered through the use of the Twilight Forest's mod's Uncrafting Table, you can take a once enchanted thaumium tool or piece of armor with repair on it and swap out it's material for diamond.
Shown below is an example. Please forgive me using a hoe as an example, but it was the first tool that got enchanted with repair
Also note that this method can be further used to get Soul Stealer on a repair item and then on a diamond sword. Also do note that enchantment level can get rather high (my pick cost 49 levels). Also this will only work on items that can have their materials replaced.