Produce a Smooth, Round Countersunk Hole Every Time. Best Countersink Available for Aluminum. Cut Degree is 82°. The CRL Weldon Countersinks were specifically designed to cut round countersunk holes in aluminum. They cut faster than standard countersinks and leave a finished hole every time. Smooth drilling action from single cutting edge prevents chatter and fluted edges. The 1/4 inch (6.4 millimeter) shank diameter fits any 1/4 or 3/8 inch (6.4 or 9.5 millimeter) drill chuck. Hole Size: For large holes