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General Mach Discussion / Re: Bit for cutting 0.008"-0.02" (up to 0.5mm) aluminum/brass/steel sheets
« on: June 24, 2009, 09:08:21 AM »
Kevin,
How small of a hole do you want to cut?
How are you holding the thin sheet metal stock?
I would probably have the thin sheet attached to a flat sacrificial piece underneath the sheet as
this way it won't spring. The anodized Al surface can be real hard so you need to get below the
anodized suface. They sell small end mills ie; 1/64" ( .5mm ), are expensive, and break in a heart
beat if you put much force on them when milling deep, and by deep i would say greater than 1/2
the diameter of the end mill. If the plate springs up or axis velocity is high or jerky movement they
will snap off very easily. High rpm and and small chip load along with coolant / cutting fluid to keep
from galling up the cutter. SS and brass will work harden. With real small size HSS end mills are
a little more forgiving then carbide ones. That spindle you have is nice and has a small runout.
Most of my experince is using a small end mill is to do engraving and and run at like
1- 5 inches / min at 28,000 to 60,000 rpm with about .003 to .005 depth of cut or less. When
drilling real small holes ( below 1/32" - #80 / .013" and even less ) i use a sensitive drill press
which i made, 28000 rpm, peck drill the metal, and actualy watch the drill via 30X so i can see if
the drill is bending. Need to let the tool do the work.
Just some thoughts,
RICH
How small of a hole do you want to cut?
How are you holding the thin sheet metal stock?
I would probably have the thin sheet attached to a flat sacrificial piece underneath the sheet as
this way it won't spring. The anodized Al surface can be real hard so you need to get below the
anodized suface. They sell small end mills ie; 1/64" ( .5mm ), are expensive, and break in a heart
beat if you put much force on them when milling deep, and by deep i would say greater than 1/2
the diameter of the end mill. If the plate springs up or axis velocity is high or jerky movement they
will snap off very easily. High rpm and and small chip load along with coolant / cutting fluid to keep
from galling up the cutter. SS and brass will work harden. With real small size HSS end mills are
a little more forgiving then carbide ones. That spindle you have is nice and has a small runout.
Most of my experince is using a small end mill is to do engraving and and run at like
1- 5 inches / min at 28,000 to 60,000 rpm with about .003 to .005 depth of cut or less. When
drilling real small holes ( below 1/32" - #80 / .013" and even less ) i use a sensitive drill press
which i made, 28000 rpm, peck drill the metal, and actualy watch the drill via 30X so i can see if
the drill is bending. Need to let the tool do the work.
Just some thoughts,
RICH