Excello mill cutting a slot with 12 solid carbide endmill

I am milling slots that are 6mm wide and 100mm long in 3mm fibre glass The end mill I am using is 6mm in diameter However when I use a

Diameter 1 Flute Carbide End Mill Slot Drill for Aluminium 5mm Flute Length Also Suitable for Plastic, Acrylic, PVC, Copper, Brass, Aluminium and

slot scalextric Helical End Mill for Titanium Alloy Machining Unique Design for Slot mill Three types full coverage range from to HS-MFAL: High

slot charter meaning HSS Slot end mills Recommended for milling in materials with medium and high tensile strength up to Nmm² Vertical cutting to full depth and horizontal