I need something that can cut down into a surface a fixed amount. Like a circular saw but tiny and precise. I’ve got a piece of 10mm ply on top of something else and I need to cut a piece from it without removing the whole lot.
There ‘s a tiny dremel saw attachment but I don’t know if it has a depth stop. There is also the router jig for it but that wont go up to an internal edge.
Not knowing how precise you need to cut, but if you bought (say) a 22mm circular saw for a Dremel, and it had (say) a 2mm spindle, your max depth of cut could only be 10mm.
Fein and things like Fein multicutters (Bosch do them in Blue and Green and corded and cordless varieties) would do the job, especially if its a reasonably short length of cut. The plunge blade is marked with increments rather having a stop though, so its a steady hand / eye thing
The blade vibrates almost imperceptibly to cut and is and is very safe to use – it’ll cut wood and steel but not meat and fingers – its the same kind of saw the gets used for removing plaster casts. Different attachments can be used for sanding and grout removal too so a good general fixing/renovating/bodging diy buy.
Otherwise an angle grinder and a thin blade (such as the ones for stainless steel) and some care would work too.
If you surf the shopping channels theres are dinky-bladed plunge cutting saw that pops up there, but not sure how close to an edge they cut.
If its a longer cut then the festool and maffel type saws can cut very close to an edge (but not flush) and can plunge and have a depth stop, and will cut a very straight, clean line (unlike the multi cutter which can hack things up a bit) but thats in the hire rather than buy price range
Can you not drill a series of small holes next to one another 10mm deep in the shape you require then use a stanley blade to break the bridges between each hole.