Whenever I see recommended drilling and turning speeds I have always assumed the figures were maximum speeds, i.e. any speed below that figure is acceptable, but now I begin to wonder if they aren't also minimums as well. I understand the idea of not turning or drilling too fast in terms of surface feet per minute at the cutting tip to avoid excess heat generation, but can one really drill too slowly?
I do realise that published figures are aimed at industrial applications where other considerations such as down time, tool durability etc. are important, so I must stress that I am not trying to replicate those speeds, I am trying to understand the principles behind them. Can anybody enlighten me?