Nairbg

I have just purchased my first industrial type sewing machine. It needs a little attention and I need some direction. First, on the back of the main casting toward the drive side there is a small vertical mounting boss cast in. It has 2 threaded holes, one over the other. I cannot determine the size or thread pitch of those holes. They are close to 6mm but they are finer than the expected 1mm tgread pitch. Anyone know what this size/pitch is? Second, my information to date suggests that a #18 needle and Tex70 thread are the largest that this machine can handle. I'd like to go heavier. Has anyone any experience/information on going heavier with this machine?