smlpdcbit ROCK REAMER #hdd#hole#opener It means that the teeth using the roller are milled teeth, that is, the teeth milled out on the matrix of the roller, whose wear resistance is relatively poor. In order to improve its wear resistance, it is often coated... moreROCK REAMER #hdd#hole#opener It means that the teeth using the roller are milled teeth, that is, the teeth milled out on the matrix of the roller, whose wear resistance is relatively poor. In order to improve its wear resistance, it is often coated with a hard alloy layer. https://www.sml-pdcbit.com/products/rock-reamer/less