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Hollow Augers

I have had quite a bit of experiencing using hollow augers. The adjustable type work as the cutter (oriented perpendicular to the axis of the workpiece) makes a spiral score to the depth of the required tenon diameter. Some cleanup with a fine rasp will be required afterwards. The cutter can be set to varying depths- set it so it just barely peeks out beyond the bore of the tenon you are cutting. The tenon will ideally just fit as it is cut, or perhaps with a slight amount of interferance that helps clean off the score fuzz from tenon. The actual setting of the bore is another adjustment, and must be done by trial and error (regardless of any calibration marks on the tool, they're just for getting you into the ball park). Set this so that you get the fit you want with the minimum amount of clean-up filing of the tenon.

The non-adjustable type works more like a pencil sharpener (not the kind you crank, the kind you had in your bookbag). The blade is oriented almost parallel to the axis of the workpiece. Lee Valley, and others, make modern versions of these tools. The advantage to the fixed diameter hollow auger is that the tenons come out ready to go, no filing necessary. You must trial-and-error the setting of the cutter depth for exact control of the diameter of the tenon. They work fast, but it isn't easy getting the tenon 100% concentric all the time.

For an older tool, I would stay with the bevel on the cutter that came with it. I would only change this angle if the tool absolutely refused to perform with it that way. As in all cutting edge tools, they need to be sharp.

Another thing you should have is a "pointer", a tool that will champher the end of the workpiece to facilitate the start. This is also one way to work towards the goal of tenon concentricity. I also have a small one that will put an 1/8" champher on the end of the tenon when its done, to help it fit into the hole on assembly.

If you find a way of guaranteeing concentricity all the time with either type of hollow auger, please let me know! GB 8/16/04


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