IF I can find it I use a professional grad ratchiting crinper I got to admit the crimps it turns out look 100% professional. I have used it on wire up to 10ga in fact teh wire is right in front of me. 40 amp poles or so they are rated.
Last pair I put on I used the "Crimp" feature of a pair of needle nose pliars but it was much smaller wire and I had do do some additional "Crimping" to get it to grip properly but its solid now. THat connection is in the other room.
Go to West Mountain Radio and look over all the Power Pole stuff they carry...