The two main advantages were they were easier to manufacture and much easier to sharpen the ends with a simple fixture on a surface grinder, or even by hand if necessary.
In the days when they were mostly made of carbon steel frequent resharpening of the ends was necessary as they got dull quickly. Much of that requirement went away as HSS steel started becoming the standard material. With modern carbide, very few small shops resharpen in house at all as it takes rather specialized equipment to do the job right. They either retire them, use them for profiling only where the end is not used, or send them out to be resharpened.
Modern manufacturing techniques have evolved to where there is no real difference in making center cutting and non-center cutting cutters and center cutting are the standard product. Early manufacture of carbon steel and HSS often started with a casting with the flutes cast in. Only a small amount of simple grinding was necessary to finish the cutter. Casting is still used on a lot of the inexpensive HSS cutters. Most of the higher end cutters are cut from a solid blank now and I think almost all of the carbide cutters. are. CNC cutter grinders are such that even when you need a special the cost is very little higher than for a standard end mill. In carbide a 5 piece order and a 25 percent premium will often cover the cost.
Gail in NM,USA
