Machining: Charpy Impact Specimens
Specimen machining shall be prepared in accordance with ASTM E23. Specimens machined by CMS use the dimensions dictated by ASTM E23 Fig 6 Type A, which is a standard size bar.
When material is received for Charpy bars, they are cut to approximate size using the Buehler 10-1030 cutoff saw or Hyd-Mech bandsaw. Charpy specimens are required to be 10 mm (0.394") square and 55 mm (2.165") long. Machinist should cut to approximate size, leaving enough material so that the precise measurements can be ground to size. The bars are then ground on the Acer surface grinder. The bars are placed on magnetic surface or clamped into vice and ground to size taking 0.001 off each pass. Notches in bars will have a centering ±1 mm (±0.039"), will be 2 mm (0.079") deep ±0.025 mm (±0.001"), have 0.25 mm (0.010") radius ±0.025 mm (±0.001), and 45 degree angle ±1. Notches will be smoothly machined using mill with a double angle milling bit or broaching machine. Identification marks for notch direction should be placed on the end bar, preventing putting any marks on ground surface face of bar. Notch direction is determined by customer or specification requirements. Notches should be measured for accuracy on the optical comparator at 20X with notch comparison overlay.
Sub-sized samples can be machined in accordance with ASTM E 23 or other governing weld specification.