Hi Lawrence,
Your machinist doesn't have the full story on the chuck used by the CarveTight and Rock Chuck. They use a "paw" to grab the bit shank. He's probably familiar with the commercial "ER"-type chuck collets (which are patented). They are waay different than a "paw-style" chuck collet, and there is really no valid comparison between the two. I use the ER chuck collets on the ShopBot and there is no slippage on any bit as long as it is tightened properly and not worn out. BTW, ER collets are a little pricey - I spend between $45 and $65 on each.