I got the 1/4" - 20 bottoming tap version. It broke after I spent 2 hours pre drilling a custom piece. I pre drilled with 1/4" drill bit to 1/2" deep for a nice pilot hole... then finished the remaining depth of 3/4" with a 3/16" bit. I was almost positive that I had enough depth. MAYBE NOT. MAYBE DRILL DEPT was the cause OR MAYBE NOT. I started tapping at low speed with hand drill but very steady with two hands and a knee on one arm bracing it with a hanging shock as a deviation gauge. After going forward and reverse down to about 1/2" of depth, I switched to high speed pausing and taking it out to re lube with cutting gel oil. Primo. It felt like I bottomed out very early. About 1/2" from the bottom of the drilled hole. I took it out. Cleaned the whole with wd-40. Then checked the hole with a 1/4 -20 bolt x 1 1/4" deep. It only went in half way. I tested the hole. The hole was drilled longer than the bolt by 3/8". What is going on? So I re tapped the hole knowing that I did not get deep enough. I was aiming for 1/4" from the bottom wall of the drill hole. I stated tapping again back and forth at high speed. As I was tapping, at the bottom/end it felt almost like the predrill hole was too small! No instructions tells you what predrill hole size to use. Needless to say. IT SNAPPED inside the hole. QWERTY!!! Luckily I used a reverse drill to predrill the hole with. I will just use a reverse drill bit to get the broken tap. So I drilled and drilled but to no avail. It would not come out. QWERTY! ASDFGH! ZXCVBN! QWERTY!!! i AM SO MAD now... I suppose I should have used a 13/64 drill bit instead of a 3/16. I DID NOT think 1/64 of an inch would have mattered but it did! 1/64 inches is only 0.3969 millimeters. This tap could not take more than that before snappo! IF THIS TAP ONLY CAME WITH INSTRUCTIONS FOR DUMMIES LIKE ME. I swear I thought I knew what size to predrill I didn't even check. I bet that is the problem everyone else is having... I was going to give it one star but I suppose I could have figured it out on my own. I just thought I knew what I was doing... I suppose I should share the blame and for that reason I will give them 2 stars!