I work in a CNC shop with high production numbers. We do have runs of parts that require a 33tooth spline to be broached 5.5mm deep. The spline constantly servo torque alarms the machines. We have to run our bore tolerance right at the top limit and pray that it works. The spline is 20mm in dia and the bore top limit is 18.5mm. This is in 1117 steel with a spindle speed of 2500rpm and a feed of .13mm/rev. According to what i can tell in the books it should be a higher feed and slower speed but this seems to be what will actually run. Going any harder with the feed no matter what the rpm is torques out the machine on the B and Z axis. The cycle time needs to be as quick as possible since we run high production and at the moment is 12.5sec. It does have a 45 degree lead in angle larger then the tips of the broach and cuts into a undercut. I dont see many issues online about broaching causing the machines to torque out. Just wondering if i am missing something. Also was looking at this as a possible solution. Broaching Tool for ID keyways, splines, and slotting. Live tool lathe powered. - MD Tooling
sandrewb,
Is this a rotary broaching operation, also do you have a chamfer on the hole? The chamfer can get the chip started and curling properly. If it is rotary broaching, .030" material removal per side is a little bit bigger than what's normally recommended. We usually only suggest rotary broaching for forms up to .025" material removal per side and .005" per rev is a little heavy for the feed rate. Try .002-.003 IPR feed rate and 700-800 RPM. (sorry for the English unit conversion, that's just what I use all day at work). Hope that helps.
Broaching questions.
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