Not sure if this is going to help anyone or not, but for a long time I have looked for any resource to file and sand inside cuts on very small cutouts.
I have tried mini files, dental files, hand held scroll saw blades, and even cutting down fingernail files.
I am working on a very intense piece with hundreds of very small cut outs. The smallest needle file at any store will not come close to getting in the areas I need to reach. I do realize that a perfect cut the first time is ideal, but few of us make perfect cuts every time.
Now for a long time I have used the opposite side of the scroll blade to "shave" down a slight bow or irregular area. It does work well but when you have say many hundreds of cuts on a single piece, you know you will have irregularities. I just don't like them, so I have looked for a long time for a solution.
Sandpaper on a scroll saw blade on the saw? Yes I do that too. Self adhesive works well and is smaller than commercial solutions.
But I needed very very delicate control over the sanding blade.
Perhaps ten years ago I bought a very used exacto knife set. The blades are now rusted and dull. But in the case there were Three mountable exacto knives in the set in good condition.
The kind that you screw open and slide the blade into the top of the knife and tighten it down. So who says an exacto knife blade has to go in there? See the pics
I took two sizes of blades from 1/0 to 3/0. 400 grit
The blades fit perfectly into the knife ends and tighten down nicely. I use used blades: Clean them and mount the sand paper.
The blades are cut in half with a fine cable cutter so as to add stability. They are sturdy enough to do extreme fine sanding with.
And you can even use the knives to put a scroll blade into and "feather" a vein. Now I can sand the wider areas on my scroll saw, and the most delicate of parts by hand. Sandpaper on only one side of the blade makes it even thinner....
Not sure if I explained this very well but if you experiment with an exacto you will no longer need to hold onto that tiny blade. Now you will have a handle and more control over your work. Try cutting the blades in half
Two knives in pics with 400 grit. One with the Exactoblade in it.
NOTE: Scroll Saw blade edges are stamped left or right, and.... This can break through the paper and damage the work piece.
Solution; Simply quick file the full edge of the blade to smooth using a grinder or file.
Exacto knives can be found on the cheap at Walmart. Say three bucks?