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Woodturning (rec.crafts.woodturning) To discuss tools, techniques, styles, materials, shows and competitions, education and educational materials related to woodturning. All skill levels are welcome, from art turners to production turners, beginners to masters. |
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The Turning Dilema - RPMs vs Risk (semi-long)
The Turning Dilema - RPMs vs Risk (semi-long)
I come to turning from The World of Norm (other heroes - Krenov, Maloof and Nakashima). I can adequately use handtools - chisels, dovetail saws, hand planes, cabinet scrapers, some carving gouges, and can set up and safely use a joiner, planer, table saw, shaper, SCMS, router - in or out of a table, drill press, drum sander, OSS. Mortising machine etc. . I’ve got feather boards, hold downs, blade guards and push sticks - and use them. I can put a good edge on just about anything flat backed with a flat bevel - using a Tormek, diamond plates or japanese water stones - with or without a jig. And I can read grain adequately - on flat stock. In The World of Norm, I can mechanically limit the degrees of freedom of movement of both the tool and the stock. With turning, at least the center/ spindle turning I’ve been playing with (for me, if it’s fun it’s playing), it’s the very dynamic brain/ eye / hand coordination that concerns me. Initiating a “cut” properly and completing it properly is requiring far more concentration, coordination and, frankly, stress than it probably should. And RPMs seems to be one of the major causes of my low to moderate anxiety. In The World of Norm, the RPMs of the thing biting off pieces of wood is typically fixed - the more teeth chewing, the smaller each bite is. The slower you feed the stock to the teeth the smaller each bite is. It’s Biting Off More Than You Can Chew which raises all the hell - and launches things - at what seems to be at least Mach 3. In The World of Turning, you’ve got but a single “tooth” - the chisel, gouge or scraper, tool angle, feed rate and RPMs determine the “bite” size. AND, in The World of Turning, unlike in The World of Norm, the “tooth” can follow the grain of the wood - and if it does all hell can break loose. And that leads to my dilema. At 500 RPMS, things happen 1/3rd slower than at 1200 RPMs - eight “bites” per second vs 20 “bites” per second. I “know” that my reaction time is greater than a half a second so when a catch happens, it really doesn’t make much difference whether it happens in 1/10th of a second or 5/100ths of a second - it’s happened before I can possibly react. Now the Mr. Spock part of my brain says “More bites per second, the smaller each bite, and, logically, that’s safer.”. But my white knuckles, clenched teeth - and sometimes “cheeks”, are telling me - “SCREW LOGIC - SLOW IT DOWN!”. So my questions a 1. Recomended roughing to round with a 1/2” or 3/4” roughing gouge RPMS, given the following: - starting with up to 1 1/2” square stock - 10 to 14 inches between centers and stock “approximately” centered 2. Recomended RPMS for spindle turning a 1 inch cylinder 10 - 14 inches long. 3. When you’re turning parts down to pretty small diameters, do you want to work at higher RPMS or lower? 4. Is “best RPMs” a function of the type of wood? I know that pine crushes rather than cuts when using bench chisels while maple, cherry, walnut and, my favorite, mahogany cut nice and clean. So much to learn, so many mistakes to try and avoid. (Turned some year old prunings from a plumb tree. Nice stuff - and FREE! Fun, this turning thing) charlie b aka The Rotationiste in training |
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