Hi,
while I use 0.5mm endmills mostly, I do use engraving bits when I require finer intertrack spacings than can be achieved with an endmill.
My experience is those cheap 10-15-30 degree 0.1mm engraving tools are rubbish, the tip breaks almost instantly and the cut is rubbish.
Try 45 or 60 degree bits, say 0.2mm, they are much more robust.
I get these from the same supplier of my 0.5mm endmills. Note they are actually double the price of the endmills, but they have proven to have good cut
quality and last for 10-12 hours cutting.
https://www.ebay.com/itm/60-DEGREE-M...72.m2749.l2649
Craig