- Topics Started: 90
- Total Posts: 1360
That is true. Also, a reamer should only remove a couple of thousandths of metal. Its purpose is only to size the hole but many people try to use a reamer as the final drill size; bad idea! I like to drill first up to about .015 inches under, then use a boreing bar to get the hole to within a few thousandths undersize, then use the reamer for the final size. For a hole requiring extreme precision such as a valve guide that must prevent oil leakage or an ejector pin on a plastic injection mold, the hole would be reamed slightly undersize (.0001) and then lapped or honed with a SUNNIN HONING MACHINE.