I make models for my supper ($) and need smaller daddos and grooves than a router plane makes. Hence my effort for a " custom " stair saw. I'd just like a selection of blades that will cut slightly larger or smaller daddos/grooves. I'm probably STILL not making any sense right ?
Not exactly, but I understand what you want to do.
Think about this. If you had a small custom made router plane, like a "Witch's Tooth", you could make blades the width that you want. You will have more control over the slot that you're making with a router plane than a saw, IMO. Look at this small router plane from LV, as an example.
It comes with a 1/4" wide blade in it, which is probably way too big.
If you made blades for a small router plane like that, you could make them as narrow as you like. I think it's important to understand that it's difficult to use such a tool against the grain (not impossible, but more difficult) as it doesn't have knickers.
What are the actual thicknesses that you would need to slot Steve?
You could make a small router plane like that fairly easy out of wood, and it would work fine for your needs, IMO.
OTOH, a saw as you've been using could work against the grain better, and in that case I would think that less set on the blade would be preferred as you will most likely not need to go too deep.
I have a Foley retoother, so can stamp teeth for blades, but the problem is in getting the various plate thicknesses. I am using .018" for small dovetails, and some folks use .020". Most steel needs to be purchsed in larger sections, and the price starts going up quickly as the thickness does. To give you an example, 8' of .018" 1095 spring steel costs about $34 from McMaster-Carr for 2" wide. For a stair saw you wouldn't need that wide, but you would need to buy in QTY.
If you went that route (no un-pun intended
) you might be able to find various thicknesses of drywall blades that could be retoothed, but those will cost about $6-$10 each also, and you'll need to cut them to width which might not be so easy without metal cutting saws. You might be able to do that yourself with a hack saw, not sure.
Interesting project. Please keep us informed on what you decide.
Myself, I think I would go the small router plane, find a used one cheap, those can be had for about $10, and make yourself some custom cutters for it. I think you would have more control over it that way.