Before I made a diamond shovel and then enchanted it, I read on the wiki that silk touch is tough to get. You need an enchanted book with silk touch for sheers. One part of the wiki said that you can get silk touch on the diamond shovel normally and with luck. I made the shovel and enchanted and it gave me Fortune II (at lease I can get more flint from gravel when I need it), unbrakeing III, and efficiency IV.But no silk touch even though I tried it from level 32. Is there anything that I did wrong or was I miss-leaded by the wiki?
My advice to get more diamonds faster is to do a branch mine at eye level of 12. Check out the wiki for how to go aboutt his if your unsure. It's also galled grid mining.
As to your topic, it's random so will take a few tried to get what you want, unless you use mods that let you pick which enchant you want (I wouldn't do it personally as I like the randomness of it, though it can be a massive time and diamond saver)
Try enchanting a Book, if you get Silk Touch, make an Anvil and convert the Enchanted book into the Shovel
^ Do not follow this advise. You have a much lower chance of getting silk touch on a book than on a shovel, so it is only useful if you have an enderman farm. Just enchant shovels. It's approximately one chance in five, last time I checked.