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In my experience, many companies do not use the recommended cutting speeds for materials. In general, it seems they opt for lower cutting speeds. Is there a reason they typically do this?

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    $\begingroup$ Listing some examples of what you have found would improve your question. $\endgroup$
    – Fred
    Feb 28, 2017 at 7:42

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By necessity recommended speeds and feed rates are generalisations and, in practice the optimum for a given job can vary a lot. Recommended speeds are typically intended to be a reasonable compromise between material removal rate, quality of finish and tool life and it is entirely possible that in certain circumstances it is preferable to sacrifice one in favour of the other.

If one machine has to perform a number of different operations it may not be practical to change the speed for each operation (especially with pulley driven pillar drills with manual ratio changes) and in this case a compromise towards the lower end of the speed range as too high a speed is likely to damage tooling whereas too low a speed will just reduce productivity and perhaps reduce finish quality a bit (although this isn't the case in all circumstances).

Or it may be a strategy to prolong tool life and reduce down-time due to tool changes and refurbishment.

Most speed tables only cover a few generic materials but the machinability of materials can vary significantly even for ostensibly similar materials and even between batches of nominally identical alloys so a lower speed may be perceived as a safer default to achieve consistent quality. It is not necessarily even very easy predict or generalise what will work best for a given material.

There is also the fact that for any drilling operation with solid drills the speed will be a compromise between the relative surface speeds across the radius of the tool which obviously is exaggerated as the hole diameter gets bigger.

Another important factor is that practical drill speeds depend greatly on the cooling, lubrication and chip flushing regime used, which can vary hugely according to context. For example a basic hand held pr pillar drill may have no cooling or lubrication but even something as simple as a manual oil dropper may significantly improve performance and at the most sophisticated end of the spectrum there is fully automated flood, mist or air jet cooling not to mention a variety of oils, cutting fluids and emulsions as well as tool coatings.

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