Cutting Tool Principles - Milling - page 109

Table 2. Cutting speeds for various materials.
Table 2 gives an indication of the speeds that should be used for various
common types of material likely to be found in the workshop. These speeds
and feeds will vary depending on the rigidity of the milling machine, the cutter
and the work-holding setup. This table is suitable for milling and drilling. For
reaming use about 25 per cent of the recommended milling speeds.
Table 2 is a guide only; the chances are, the speeds available on the milling
machine will not be exactly the same as required. It is a case of 'near enough
is good enough'. Set the milling machine to the next available speed lower
than the speed shown in the table for the diameter of the milling cutter and
the type of material being cut for HSS tools.
For using tipped tools in the small workshop, rather than an industrial en-
vironment, I suggest doubling the speed used for HSS tools and use a feed
rate of about 0.001in (0.025mm) per cutting tooth as a starting point. So, for
a four-flute end mill you would use a feed of 4 thou (0.1mm) per cutter re-
volution. You can always adjust the feeds and speeds up and down to suit the
cutting circumstances.
CUTTING LUBRICANTS
To get cutting tools to cut easily it is advisable to use a cutting lubricant. Cut-
ting lubricant will also extend the milling cutter's working life.
For steel I usually use neat cutting oil as a lubricant, although it does not
cool the work as well as soluble oil. Water-soluble coolant is normally used
in industry. This is usually oil with a chemical (a detergent) that makes the oil
emulsify in water so that it will lubricate and cool the work. Synthetic soluble
oils can sting your hands if you have any open wounds. Soluble oils on the
milling machine can wash the lubricating oil off the slideways and encourage
rust, so use it at your own risk.