This is an article written by Channel Island Woodturners. However when Stuart Batty Visited us last year he went over the same information on tools and grinding
1) Gouges: He recommends that the gouge be ground at a 40°-42° angle. His optimum angle is 40°. [He uses this on the spindle roughing gouge, spindle and bowl gouges and only switches to a 60° grind for the very bottom of a bowl.] Below 40° the gouge gets too aggressive and grabby. He also grinds away the bottom of the bevel at the gouge nose so that he can make tighter curves inside a bowl. He sharpens often [free hand without jigs] and always before the final cut.
2) Types of cuts: He uses the push cut mostly since it produces a cleaner cut and doesn't tear out end grain but he uses the pull cut to rapidly remove material. When using the push cut, the hand guiding the tool at the tool rest is used primarily to keep the tool on the rest. He emphasized not to push the gouge into the wood but to let it cut at its own speed. When the gouge is pushed into the wood [by riding the bevel too firmly] the wood at the point of contact is compressed and this will result in uneven cutting and produces an undulating surface (I'm an expert in this technique.) He showed that when this occurs, stop, back up and gently cut through the undulation. Feed the gouge slowly over the surface for the best finish.
3) Tools and Sharpening: He uses M-2, M-4 and A-11 steel tools. He believes that the higher Vanadium steels become more brittle and doesn't recommend V-15, 2030 or 2060 tools. For sharpening he recommended SG ceramic aluminum oxide abrasive wheels that are J or K hardness and stressed never grind on the side of the wheel. He pointed out that the color of the wheel doesn't tell the full story and it is necessary to read the label on the wheel. [SG stands for seeded gel- see comment section below the photos*.] He uses 46-60 grit to shape his tools and 80 grit to sharpen them. He uses a fine diamond dresser that has a rectangular cutting edge and slides the dresser across the wheel. As a safety feature when he first mounts and turns on a new wheel he does this from behind the grinder to prevent accidents from a wheel that was cracked in shipping. Also don't over tighten the nut holding the wheel (the paper on the side should be left on both as a cushion and to identify the wheel) as this can crack the wheel also.
4) Chucks 4-jaw and jam: Always make a square shoulder on the wood to seat properly on the 4-jaw chuck. The chuck has to fit against the wood shoulder in order to work. [See the handout that Al has brought to the past two meetings regarding proper use of chucks.] When he uses the 4-jaw chuck, the jaws are nearly completely closed in order to achieve maximum gripping of the wood. He doesn't orient the wood grain in any special way in a 4-jaw chuck. For jam chucks he makes a positive shoulder and a constant size inner diameter body which projects ½" ± beyond the shoulder into the work piece. This projection will keep the piece aligned on the jam chuck if it moves slightly away from the shoulder. He also used masking tape to secure his pieces to the jam chuck.
5) Tool use: Stuart believes that the length of the tool handle should be longer as more of the tool hangs out over the tool rest. He expressed this in ratios which were hard to follow, but as two examples, he thought the handles on parting tools (particularly the 1/16" thick short ones) where much too short since even with the tool rest close to a spindle, you are parting to the center line and the tool is way out over the rest. Also he felt that the handles on some spindle gouges and beading tools were too long since the tool rest is near the work and a long handle hits your body when you are trying to do fine work with your hand and wrist turning the tool, unlike bowl turning where a long handle is ideal and braced against you hip as you move in an arc in front of the lathe as you rock from one foot to the other as the cut proceeds.
He uses the skew chisel only for lay out and shear scraping. For pommel cuts he prefers the spindle gouge and for beads either the spindle gouge or a Bedan type square beading tool or parting tool. He doesn't like the diamond shaped parting tools because the two sides are often asymmetrical and thus wider than the actual cut. Since the typical roughing gouge has a small tang in relation to the size of the gouge it is prone to breaking and should only be used for spindle work when taking square stock to round. A thick bowl gouge does the same work and is much less likely to break.
|
| |
|
