I buy M6 taps and other as needed taps at a hardware store. Look online for the correct drill bit size for a 75% thread which is what most are and buy as needed. The sets will be cheap unless they are a good name. I have an M6 die that I use to clean threads. Comes in handy. Hanson brand is pretty good. Use a tap wrench and oil, they break easily if forced from side to side from using pliers or other incorrect tools.