persianmd2orchard,
If you are just grafting pome fruits (pears right?) you can probably use the factory edge without any increase in failure. They are very forgiving, I have even heard some very experienced grafters suggest "You could probably graft apples with your teeth". Though, as Vince pointed out, you are putting yourself at more risk. $50 seems pretty cheap after going in for stitches ;) You also don't need an expensive stone to get started, there are plenty of less expensive options. Pretty much any reasonable fine sharpening stone will allow you to make a large improvement over the factory edge.
The sharpening steel you have for your kitchen knives does not perform the same function as a sharpening stone/hone. The sharpening steel essentially "combs" the kinks out of the edge of a knife that it acquires during use. Where as a hone actually removes metal to create a sharper edge.
I would strongly discourage you from using the sharpening steel on your grafting knife. To work correctly the steel composition of the steel needs to match that of the knife. A leather strop, like the paddles shown in the video, are what you use with a very fine edge.