Review on Z Threaded Insert Internal Threads by Marco Habersham

I was initially skeptical of the amount of hole to drill and that no inserts were included. One reviewer advised using a 14mm Forstner bit, and he was right. I drilled a maple glue countertop so this was the worst option for super hardwood inserts. The 14mm bit worked perfectly and the inserts screwed in easily. I also bought a drill adapter specifically for bits that costs $10 a bit, it made turning bits very reliable. Make sure you turn the drill on at low speed and start very slowly, making sure you go as straight as you can be with a hand drill. Low and slow is key for these inserts, don't try to spin them at high RPM. I only screwed up in 1 of 12 and that's because I started crooked and while I was able to straighten myself up when I left, no you should come right back and start over. I barely got the insert out because the adapter bit is for insertion, not removal, it tore the top edge of the insert but pulled out. Again, this was only because he initially placed them crookedly, I was able to easily remove the ones that were just in place. All in all this product worked great as did the extra adapter which is a must have. It's also worth noting that I bought an M8 bolt insert, the adapter fits into a 14mm pocket so the insert can be rotated flush or even under the surface if required.