Rabbet or fillester?
Adam Cherubini
>I...sawed down the end (grain?) and across the grain with a back saw
Are we talking about rabbets or fillesters (rabbets oriented across the grain).
If we are talking about a fillester, I can see why you wouldn't want to use your #78. And yes, I can think of several reasons why the approach you took isn't a great idea. Before we get to that, there similarly several reasons why you wouldn't saw out a rabbet in a cabinetshop.
In general, rabbets and fillesters are related to an edge, both in terms of its shoulder and depth. Using a saw to create these features instantly and permanently removes this relationship, forcing you to use up your skill to create a decent feature (I only have so much skill to use each day and I try to spend it wisely). I sometimes make rabbets with a chisel which is a similar methodology.
I recommend getting yourself a real rabbet plane with a wide open mouth. Rabbets are more akin to scrubs than smoothers. No way can you saw a rabbet as fast as you can plane one with a good rabbet plane.
Now if you are talking about sawing fillesters, I can see why you would use this approach. No rabbet plane is going to do a good job of this. The answer here is the PURCHASE OF AN ADDITIONAL TOOL. That's right! You heard me correctly. In fact, I presume to speak for all of us on this matter. Your actual creation of this feature permits you to purchase a moving fillester plane (of a variety of your choosing).
Here's why you don't want to saw these things. Sometimes you need a long one. Using your back saw like a stair saw is a real drag. Also, wood tends to cup in this direction. You can often clamp this cup out without resorting to machining it away (which doesn't fix the problem in the long run anyway) Its easier to plane the clamped board than to saw it in two planes (faces).
I could go on- maybe somebody else will, but fillesters are to be avoided whenever possible. When encountered, I've found it best not to mess around with them. A fillester plane (tho slower than a rabbet) is the best way to create these features.
Adam