With Heat Shrink fit tool holders, vibration is reduced and cutting is noticeably faster and smoother.  Heat Shrink Technology uses expansion and contraction properties of metal to provide extremely powerful tool holding.  The bore is slightly smaller than the tool shank, and when heated, it expands just enough to allow the tool to be inserted.  When it cools, the contraction of the metal holds the cutting tool with 10,000 lbs. of force. Some features and benefits include:  increased feeds and speeds, eliminates slippage, eliminates collets and nuts, works with carbide and HSS tools, improved accuracy and repeatability, improved carbide tool life and tooling costs, and increases spindle bearing life.