Okay, I'm new to this stuff, but I saw a useful technique on YouTube regarding how to make up small PCBs using the 'Island' (or Manhattan) technique. Using a small cutter of sorts with a plain copper-clad board to create small isolated pad to solder to. Great! But um, where to get a suitable cutter? I saw diamond impregnated hole-saw type things described which didn't really sound suitable to me, so I decided to make my own. I'm more engineer than electrician anyways :-)
For a first attempt I used a piece of 3/8" dia round tool steel (low-carbon Silver Steel) and drilled a 5mm hole in one end and turned the outside to some rough diameter which would create what I thought would be a suitable sized 'moat'. I cut the teeth off-hand (I didn't use any indexing tools, just done by eye), the cutter was a dovetail cutter mounted in my mill and the workpiece only roughly aligned to produce cuts in the end of the tool which would produce relief angles to the cutting edges. This was a 10min job only :-) Then I hardened the steel right out (heat to cherry red and drop into cold water) - no need for tempering.
Well the cutter worked and produced nice round pads (photo).
So that was good but there were a couple of issues: there was no control over depth of cut and it was tricky to cut an island exactly where I wanted it (difficult to judge position). I moved on to a Mk.2 version, and here I included a spring-loaded plunger with a 60-degree point which allowed me to centre the cutter exaclty, and I also added a sleave which controlled the depth of cut (0.050" inch). The sleave is made of rather strange stuff you don't come across often - it is bronze-loaded PTFE, and this stuff has the lubricating properties of PTFE but with much improved mechanical strength. So with this sleave I can ignore worries about cutting depth - just drop the tool onto the board and the sleave ensures the perfect cut depth. Again, the cutter was made from silver steel but this time I tempered the steel as I expect to keep it for a long time. The teeth can be sharpened if needed with a small slip stone or diamond file, fibreglass is very abrasive but provided this cutter is run cool (so it doesn't lose its temper) it should be very durable.
Anyway, I made my first board with it - a crystal tester :-)