Weldon Flat

This is the formal name for the flat on an endmill shank.  I have whined in the past thst 1/8" carbide endmills seem to not come with Weldon flats.  Grinding one on produces a less than perfect flat.  Today's attempt created an endmill that when tightened down was not concentric so not worth using.

I ended up using a 3/16" carbide endmill instead.  Even in a drill chuck instead of an endmill holder concentricity was not obviously defective. Larger diameter means I am wasting more material but it does fall out of its holder.   On the other hand, it is stronger and seems at little risk of breaking even at a higher feed rate.

So I asked ChatGPT about this problem.  Apparently, Weldon flats on 1/8" endmills are rare, and non-existent for carbide.  It may make more sense to buy a 1/8" HSS endmill and just accept that it will wear out quickly on CFC.