Wanted: an 1/8 inch or so hole in the porcelain of a bog cistern.
I've used this tile-hole cutter drill-bit on tiles before with no problems.
But on cistern porcelain got through the glaze ok but no further in than
about 1/8 inch deep.
I've not tried sharpening as it doesn't seem blunt and I've tried oil,
then, water as cutting medium but no further in. Anyone been here before ?
Correct drill speed ?

Seemed a neat idea for making a 2-level flush from an old simple flush
mechanism.
Pass a brass rod through the cuistern lid , located onto the ball of the
float valve.
Then add a weight to the brass to depress the float more, for more water,
until the excess weight is balanced off. Remove the weight for cheap-skate
flush.