Sometimes solutions are so simple you wonder how you ever overlooked them. I make a lot of bowls. My gouge technique is not so perfect as to leave an interior free from ridges so I frequently use a scraper. Both the interior and exterior of bowls have given me a problem with end grain tear out. The gouge or the scraper just makes ragged tears in the end grain and the more I scraped the worse they would become.
I had read of some solutions. One was to put oil on the problem area and then scrape. Some say that water will also work. This softens the fibers and make them easier to finish cut. I have tried these with modest success but in reality they are very messy.
Another suggestion was to make feather light cuts. That is easy to do when cutting with the grain but when you get to the end grain the gouge or scraper just seems to want to dig in and make the problem worse.
To sand out these areas of end grain tear out is laborious and time consuming. The dust it generates is just no fun. After years of turning bowls I seemed to be no further along.
I belong to a local woodturning club here in Vermont. It is the Woodchuck Turners of Northern Vermont. One of the functions of a woodturning club is to bring in demonstrators who have gained proficiency in some area of the craft. Our most recent meeting was host to Rich Detrano (www.richdetranowoodturner.com, e-mail: firstname.lastname@example.org) Rich does lovely hollow turned pieces.
Rich was demonstrating how he does hollow turning for people in the club who wanted to learn the skill. What I learned from Rich was so simple but it hit me like a ton of bricks. He said the solution to most problems on the lathe can be solved by slowing or raising the speed of the lathe or by raising or lowering the tool rest or by moving the tool rest closer to the work or further away from the work.
Now that is pretty simple and straightforward. I had learned that to scrape properly, your tool cuts better when it is presented to the wood somewhat above the center of the axis of rotation. If it is below the center it will just rub and not cut at all.
I had also learned that if your tool was too far over the tool rest it tended to be hard to control and took a lot more work. So I had learned to move the rest closer to my work and enjoyed the results of this simple adjustment.
When turning I generally wanted to cut as quickly as possible. So I would push up the speed as much as I dared. Never, in my wildest dreams did it occur to me to slow the lathe when I scraped. When I did, scraping became a joy. Instead of vibrating over the end grain tear out it tended to cut right through the irregularities. The shaving were very fine and with repeated passes I found that I could eliminate the tear out better than I ever had before.
When you think about it, it makes perfect sense. The faster you drive your car over a depression, the higher it bounces. When it comes down, it comes down harder and tends to dig the next rut. This is how you end up with a “washboard road,” the kind of dirt roads I learned to drive on as a kid. Just like that when the scraper or gouge hits a rough spot of tear out at high speed it tends to bounce off the rest and then it comes down hard to dig into the next area of end grain. Thus the end grain tear out gets perpetuated and even made worse.
By slowing the lathe speed, and you can adjust what speed works best for you, the tool cuts evenly and does not vibrate and you have greater control.
How I could have overlooked something so simple all these years is beyond me. I don’t ever remember reading about this point although I may have and it didn’t register. So I am very grateful for Rich Detrano making this point so clearly and succinctly. To solve problems, slow the speed, raise the speed, lower the rest, raise the rest, move the rest closer or further away.