Many manufacturers sell hollow chisel mortisers used by woodworkers to cut square hole mortises for mortise and tennon joints. This mortiser is available from www.WoodworkerSupply.com . I use this model in my shop and recommend it. Though it might be very adept at chambering, I do not use it for chambering balsa boards. I still prefer using the router for chambering, as it is quicker and more efficient in my opinion.
