in good times when buds are swelled and rootstock is flowing juices, most grafts would take, if not, a good grafting tape seals the moisture and prevents the wood from drying out, thereby increasing the chances of success. Grafting is fun, you will love it. Mangoes are not so easy to gain success, I have had 100% at times and then under 30% at other times depending on when I grafted. You learn by practicing it.