I had done this set for a PITH about 2 years ago with both bleached Wenge (right) and bleached Black Palm (left).
From my memory, the Black Palm took MUCH longer to bleach than the Wenge. I turn between centers without bushings, and just use digital calipers, so I turn the blanks to close to size, maybe .030 or so over final size, as the bleaching process will swell the wood a bit, so your nice smooth blanks will not be quite so smooth when bleaching is done. Also, the bleach will never penetrate enough to do it with square blanks unless you want to try vacuum or pressure, but you are also going to need to remove the bleach after it's done, which is going to make that difficult.
I just use a small tupperware container, put the blanks in it and add strait laundry bleach until the blanks are covered, and (with the lid on) stir the container every so often so there are no dead spots like where it touches the bottom of the container. The Wenge bleaches nearly completely in about 2 hours, but I think the Black Palm took overnight or maybe even longer. After I take them out of the bleach, I run them under warm water for a few minutes and then sit them on a paper towel on the window sill to dry for a few days. After it is good and dry, drop it back on the lathe and finish it. Remember you've only got a little bit left to take off. The more you have to take off, the more likely you are to take it down beyond the penetration of the bleach. You should be able to take the turning down to within the amount you usually sand to, especially with Black Palm, I generally sand as little as possible as the dark parts are SOOOO dense and the light parts are SOOOOO soft, that too much sanding will cause the soft areas to erode away from the dark areas...
Good luck, and have fun... it is a fantastic look for these interesting woods...
