Drilling in tough metal, including heavy-duty abrasive alloy metal drilling on hardened steel. High Quality Material. High Speed Steel Cobalt M35 Cobalt Steel Best Material. High Efficiency In Drilling Metals, and Stainless Steel. Reduce the processing cost per hole. Real 13/64". 13/64" equals to 5.16mm. Exact size is 5.16mm, tolerance 0.02mm, we rounding it up to 5.2mm. Please confirm the size before ordering.