For light use only. I made a regular cut down the side of a 1" piece of 1018 steel and my 1" 4 tooth end mill came out of the collet. The depth of cut was only 0.010 inch! I screwed it in very tight, but the collet only grips about an inch of the end mill. It did a really good job cleaning .010" topcuts, but the collet flexes way too much when you push a decent load on it.