I'm trying to make a gang type fixture for machining a slot on the end of several (10)1/2" diameter steel shafts. My idea was to take two 1/2" x 3" x 13+ long steel flat bar pieces and bolt and dowel them together. Then drill ten 1/2" holes along the 3" width so that each plate has half of each hole, or a 1/4" radius. Then mill about ~.010" off of one side so that when the plates are bolted together with the 1/2" shafts they are captured and clamped in a 'sandwich'. This assembly will then be doweled/mounted on the mill table so that 10 of these shafts can be slotted with a slitter saw using the power feed etc... A second duplicate 'sandwich' fixture will be made so that while the machine is cutting one set of shafts, I can be unloading/loading another set of shafts. Obviously, these are production parts.
The trouble is that when you remove all that material off of one side of the plates, they warp up like bananas. I first tried to drill the holes by bolting each plate together and drilling ten 3" deep holes, no luck, both plates warped badly when unbolted. Then I tried using a .5" ball end mill to machine the 1/4" radius in each plate while held flat in the vice, still warped up. I'm stumped, I've been using coolant and low RPM's to keep the material from getting hot while machining, but no luck.
Other than redesigning the whole fixture and using 1"+ thick plate rather than .5" plate, I don't know what to do. Any tricks/ideas on how to keep this material from warping? Thanks for any tips.