I've been reading about downcuts bits. If it packs the sawdust to hold a work piece will a vacuum defeat the purpose?
The idea is that the engagement direction- where the sharp edge of the tooth first cuts into the workpiece- holds the workpiece and leaves a clean top edge, not the sawdust packing. Air blast and vacuum to ensure maximum chip evacuation will be critical to avoiding chip packing, recutting, and rubbing- all of which will burn up bits quickly. Proper toolpathing in CAM is also important- you need to create or leave space for the chips to exit, and CAM is the point at which you have the most control.
I've come across a few people who advocate packing dust into a slot with a downcut bit to avoid having to use tabs. Please don't- in addition to the points @Rob Taylor made it is dangerous and could result in a part flying across the room (and potentially eye damage). Alex.
