Work holding ideas for a granite bed router
Posted: Wed Oct 25, 2023 1:23 pm
I built a granite bed router, partly as a challenge, and partly to not build another due to the first not being sufficient. With it done now (as done as any home-built machine ever is), and with basic checkouts nearly complete, there's the issue of work holding. The router will be used to machine wood, plastic, and aluminum. There are many YT videos on hold down solutions, but they all seem to focus on spoil boards in machines used solely for woodworking.
The current thinking is to start out by boring four holes in the corners of the granite bed, just outside the work space so the cutter can't contact the bolts. Epoxy in threaded inserts (or studs), then bolt down either an MDF or aluminum tool plate. Either can have threaded holes place wherever, but this is where I'm confused: the granite (a used surface plate) is extremely flat, yet bolting down very non-flat MDF or aluminum sheet seems counter productive. The purpose of the granite base was to have the mass and stiffness for a better surface finish and to lessen chatter, but don't know how well that's succeeded yet, but I find it ironic how an ultra-flat surface isn't necessarily benefit. Yes, future additions may include mounting holes for one or two machinist vices, so for that it would be a benefit, but otherwise, surfacing a spoil board seems like it offsets the same benefit as having an uber-flat surface below.
Sorry for the muddled thoughts; this is mostly a stream of consciousness post, but I suspect some of you have similar machines and have figured out a good solution. Please share so that I don't waste time going down badly-considered rabbit holes.
The current thinking is to start out by boring four holes in the corners of the granite bed, just outside the work space so the cutter can't contact the bolts. Epoxy in threaded inserts (or studs), then bolt down either an MDF or aluminum tool plate. Either can have threaded holes place wherever, but this is where I'm confused: the granite (a used surface plate) is extremely flat, yet bolting down very non-flat MDF or aluminum sheet seems counter productive. The purpose of the granite base was to have the mass and stiffness for a better surface finish and to lessen chatter, but don't know how well that's succeeded yet, but I find it ironic how an ultra-flat surface isn't necessarily benefit. Yes, future additions may include mounting holes for one or two machinist vices, so for that it would be a benefit, but otherwise, surfacing a spoil board seems like it offsets the same benefit as having an uber-flat surface below.
Sorry for the muddled thoughts; this is mostly a stream of consciousness post, but I suspect some of you have similar machines and have figured out a good solution. Please share so that I don't waste time going down badly-considered rabbit holes.