Looking at the geometry on multiple flattening bits, it appears that it’s possible to “high-center” bits that don’t cut all the way to the centerline, creating a cylindrical pillar during the plunge that could get hung up when horizontal motion begins. For example, this Amana bit has such a “dead zone:”
You are correct. Low DOC is the way to go, UNLESS you are using a program that allows you to specify ‘side entry’ into your stock. ‘Side entry’ isn’t an option for the spoilboard, so low DOC is the correct way.
It’s also why these bits do not work well with the BitSetter, unless you modify the BitSetter (or its position) so that the ‘touch’ is on one of the cutting edges.
The carbide insert bits are nice but there are other bits that have carbide that do not have the “Dead Center”. I have a Whiteside 6210 that is a plain carbide bit but has a depression in the center that makes the BitSetter useless.
Check out this tool as a comparison. This one is hollow in the center which has the same issue as my Whiteside but usually during flattening of the spoilboard I remove my BitSetter so I do not accidentally hit it when coming around the front side of the spoilboard.
One more lesson I have learned with fly bits is a high IPM to prevent burning of wood material. It is not an issue with MDF but for flattening wood projects a low DOC and a high rate of feed keeps the burning to a minimum.