STW being the font of all knowledge, I present you with today’s conundrum.
A friend has asked me to modify a diamond mortar rake bit to fit his 1/4” palm router. He makes wooden signs with lettering routed using framed stencils and a carbide router bit. The router bit doesn’t have a bearing to follow the stencil, he just uses the shaft of the router bit as the guide.
He now wants to try the same idea on some sandstone. The diamond bits he’s got cut fine, if a little slow. But the diamond bits he’s got are approximately 10mm radius head with the diamond coating extending up the shaft by 40-50mm. He’s asked for the diamond coating to be removed and the “guide shaft” machined down to 1/4” diameter.
I’ve had a go with a couple of tools to remove the diamond coating, but everything I’ve tried has bounced off the diamond and worn whatever cutter to nothing almost instantly. I’ve tried a couple of grinding wheels, it just dressed the wheel, a carbide tipped turning tool, again it just ate the tip. The body of the mortar rake is fair soft steel, it’s just the coating that’s, well, diamond hard.
Any suggestions as to what I could try next? I hate giving up so easily.
Er, that's the entire point of diamond tools - there's literally nothing harder.
A diamond tipped grinder tool will probably do it but effectively you'll be wearing/cutting both tools equally, assuming both are about the same quality.
Can't he just use a template collar?
Given the cutters are intended for use in an angle grinder it's maybe a better solutions to make some sort of adaptation / bracket for an angle grinder so it can follow a template in the way a router does. And as Josh suggests - a collar that follows the template - with the template cut to a vector offset outside your final artwork to suit.
That way the adaptation only has to be made once, rather than every time the bit needs to be replaces. I'd also be nervous about re-shaping the shaft of a cutting tool and having any liability for it then failing
