Bicycle Aluminum Profiles,Standard Aluminium Extrusion Profiles,Extruded Aluminum Profile,Black Anodized Aluminum Profile Guangdong Jihua Aluminium Co., LTD , https://www.jihua-alu.com I have a product part that needs to be modified, from the original hole size φ11.2_0~(+0.24)mm to φ13.9_0~(0.27)mm (Fig. 1), the batch is very large, the material is phenolic glass fiber reinforced plastic ( Commonly known as FRP). The material has poor machinability and cannot be machined by using a twist drill to ream (because the twist drill has a spiral groove, it is easy to get stuck). We have used flat drills made of high speed steel to expand