Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Revised my review

Previous review..."Work good for mild steel and softer. Overheat on harder metals as expected. Great for the price on proper material."After using these bits for a few months to drill lathe center holes, I have to revise my 4-star rating. When drilling mild steel I have had the tips snap off (even the largest size) with only light pressure on my tail stock screw. They seem to be very brittle. After the first one broke I was very careful to set my rpm, but then had another one snap. Bought some Keo replacements at my local tooling supply shop and have had no problems since.For precision pilot drilling for drills in my mill, I long ago switched to using spotting drills. Check this out on any of the machinist forums.These center drills do work fine for aluminum and other soft materials.