That's not so difficult for those of us who have dealt with it for unmpteen years. Conversion factor from inch to millimeters is 25.4
11/16" = .6875 = 17.46mm which will still be a tough find.
17mm = .6693 , (divided by 25.4 to get that). Could be close enough for rubber bushing versus a twist drill.
18mm is more over the 11/16" at about .708" . A tad tight or a tad loose are the metric options. 17mm Drill Bit High Speed Steel Shank Twist Drill For Wood Copper Plastic Alumin | eBay
