Sharpening – Why So Often?
When I first began learning to turn wood I got to watch Nick Cook give an incredible demonstration to our general interest woodworking club in a member’s cold dark basement one late December morning just before the New Year. I commented that my tools never cut like his! He asked me how often I sharpened my lathe chisels and my reply was truly novice; “They came sharpened when I bought them years ago. They are Craftsman so they have to be right.” Obviously my garden hoe would have been sharper.
Some days it seems like we sharpen more than we turn. Why? It is MATH and nobody likes math, except maybe me. The bottom line is this:
At normal turning speeds for a bowl blank 10” in diameter 4” thick, every 15 minutes of turning you pass 39,270 feet of lumber past the cutting edge. That translates to almost 7.5 miles of wood traveling at around 30 miles per hour. Every minute almost ½ mile of wood passes by the cutting edge of your lathe chisel.
No wonder we have to stop and re-sharpen our high speed steel tools once in a while! I’ll include the calculations at the end of this article if you want to do the math yourself.
It is rare that I can turn an entire bowl without re-sharpening my bowl gouge at least once. Now we know why. Dry seasoned wood is much more abrasive to the cutting edge than green/wet wood so I don’t have to sharpen as often. Think of a nice new interstate highway surface vs. a gravel road. Scraping cuts dull an edge even faster. It is always recommended that we sharpen our bowl gouges or scrapers just before we make that last finishing cut so we make the best cut possible. We can draw several conclusions from this new information:
Every turner using High Speed Steel lathe chisels will need a good sharpening station. Every turner will need to become proficient at sharpening. Some turners will opt for “Carbide Only” to avoid any sharpening at all. Most turners utilize some type of sharpening jig and/or set up aids in order to reduce the amount of time at the sharpening station. HSS tools are consumable and will eventually wear out and need to be replaced. Some types of steel hold a sharp edge longer than others. Turners need some method to achieve easily repeatable grinds for their tools. Sharpening is one of the core turning skills.
So the next time a new turner asks about the importance of sharpening their HSS lathe tools, you can tell them exactly why it is so important. Remember that wherever you go, there you are.
Here is my inspiration for this message:
(Even God Sharpens His tools)
Ps 7:12 HCSB If anyone does not repent, God will sharpen His sword; He has strung His bow and made it ready.
Ecclesiastes 10:10 HCSB If the ax is dull, and one does not sharpen its edge, then one must exert more strength; however, the advantage of wisdom is that it brings success.
Proverbs 27:17 MSG You use steel to sharpen steel, and one friend sharpens another.
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