Dear Wayne Thank you again for the input. As you pointed out, rigidity is key in any boring operation. Therefore, I intend to build my line borer for maximum rigidity for a given hole size, or narrow range of hole sizes. That is, I would much rather have a range of boring bar diameters that closely match the hole to be bored, so that the tool has: minimal overhang, maximum support and maximum rigidity. Keeping in mind that the hole one is trying to bore is far from round in the first place, these factors are extremely important to good tool life, depth of cut and surface finish. With regards to a removeable, clamp-on holder for the purpose of securing the tool bit in larger diameter holes, the inside diameter of it might be on the order of 2.5" to 3". I mention this to give you an idea of the scale I am thinking of. With the 3" bar, I would feel comfortable boring a 6" to 8" hole, depending upon the out-of-round condition of the hole. I will fit this mechanism with both hand feed and variable power feed, perhaps with limit switches for unsupervised use or as a safety back-up (*NOT recommended, but long holes are unpleasant and girls are distracting*). As you suggest, power feed is the best in an application such as this. For everyone following along, the tool bit could be H.S.S. (High Speed Steel) if the steel you are boring is on the softer side, but carbide bits would be prefered if they are of the type that can tolerate interupted cuts. I realize that a set of boring bars from say 1" to approximately 3" and possibly larger is cumbersome, but it would make for an effective tool for most jobs encountered. I welcome any further suggestions you are willing to make, and I will certainly pass along some pictures. One may even show it all nested in a wooden box just for the hell of it. Thanks again MetalZ
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