>>I have cut the small branch on a slant and insert itMany make it like this but not finished, 2 side cut's are important when bark grafting to get good cambium contact, see first picture.

Here is a link that might be useful: Konrad's modified bark grafting

thanks Konrad,so make the slant cut then square of the sides a small bit ,then slip in behind the tee cut. When you make your tee cut do you cut right to the wood or do you leave a little bit of soft tissue on the main trunk and slip between that and the bark.

For a bark graft you should due it when the sap is flowing and the bark slips.

If I understand what you are saying you should cut all the way to the wood. The bark should then peel back easily at the cambium layer. So there will be cambium on the underside of the bark and on the outside of the woody area.

It sort of sounds like you are trying to slip a scion into the bark of an untrimmed limb or trunk...like adding a brach? I forget the name of that graft but it is not very common in apple and a bit tricky to do. Not a graft I would suggest for your initial attempts. Also you can't use a "small branch", just a small piece of a small branch (the scion) and it should only have 1-3 budds on it.

That approach is more common with just inserting one bud removed off a scion into the T cut, and that usually gets done in summer (budding)

If that is what you trying, you will need to modify the scion more as Konrad suggests, scraping or shaving the sides, and also likely cutting a another slope on the opposite side of the scion to assure that the cambiums not only touch but actually have some degree of overlap.

There are many many types of grafts. My first suggestion would be to do an image search for fruit tree grafting, The most common are :
whip and tounge, cleft, and bark grafts with each having it's own variations. But these common basic grafts are much easier to learn with.

Any graft that requires you to separate or lift the bark (only some do) needs to be done when the bark is "slipping". The bark and the bulk of the cambium will lift off the true wood below.
Work fast,make smooth cuts, use clean sharp tools, avoid touching the cambium with your fingers. Seal well and tightly when done.

Yeah..right down to the wood.