Having never used a mortising bit, and having seen the very angled bottom ends of bits like this - CMT 801.817.11 Mortising Router Bit 1/2-Inch Shank, 1-1/4-Inch Cutting Diameter, 1/2-Inch Cutting Length - Amazon.com
- I'm a bit confused as to the difference.
On one hand (ignoring non-plunge straight bits), what is the difference beyond straight bits being relatively narrow and deep vs. mortise bits being relative shallow and wide?
On the other hand, what does the blade angle on the bottom of a mortise bit like the one above do the the shape of the cut, and is that the difference?
Next, which of these bits to use:
I want to make some very large-radius (vertical edge) corners on a box. The box will be well taller then the longest straight or flush bits, and obviously with enough layers (of MDF) to have meat in the corner to cut away. I would cut these layers slightly above size, perhaps bevelled a bit with a chamfer bit so that after assembly, the corner just looks like a slightly pixellated radius. Then, the box would have to be suspended by pivots at the axis of the intended radius at the top and bottom surface, and aimed at the bottom of the router bit, and turned within a 90-degree range, and shifted over time so that the router eventually cover and planes the entire "height" and angle range of that corner - a bit like a limited special case of router lathing.
A bottom-cleaning bit, rather more expensive, would make for a flat cut on its entire surface, thereby smoothing a largish stripe of wood on each pass - but perhaps so much that the wood has to be moved quite slowly.
A plunge-worthy straight bit would be heavily used at its usually least-used point, though (particularly if small-diameter) it might get rid of more bulk quickly when moved up and down the corner rather then turning on the pivot.
While I'm not sure whether a mortise bit is primarily intended to cut down by plunging vs. cut sideways by moving around in the template, as compared to a straight bit, it seems that if the angled bottom edges do not affect a flat-bottom cut, it might be the best compromise for this task.
Any advice would be appreciated. Please correct me where I'm wrong.