Thursday, February 16, 2017

Fiddleback


The wood pictured left is Big Leaf Maple (Acer macrophyllum).  This is a picture of break because the tree was hanging over power lines and was pushed  over with an excavator; it shows the grain very well.  This grain pattern is referred to as "fiddleback" and if the wood is cut the opposite direction, 90 degrees to the grain in the picture it is referred to as "quilt" or sometimes called "turtle". These terms may vary between localities and industries.

The fiddleback is formed when the tree or part of the tree is under compression pressure.  This  particular tree had been blown over in a wind storm when it was much younger and then continued to grow twisting up towards the sunlight causing  pressure were the tree turned upwards and grew larger.  Sometimes this will occur when a tree growing in a forest becomes shaded by other trees, and as the tree grows it will twist and turn to find sunlight causing pressure where the tree bends. You can also find this type of pattern under large limbs that are putting pressure on the bole.  Very often this pattern will not be visible through the bark. Look for the pressure points.

A bowl  turned from wood near the break is pictured below,  about 13 inches in diameter.   Maple Bark on a natural edge will not stay on the edge of a bowl.

Other Species can also have this fiddleback grain pattern.  Trees that grow on a ridge top or high point that is subject to winter storms tend to have a hard and tough grain.  Trees that grow in lower protected areas tend to have a softer and more consistent grain.  Trees that grow under the forest canopy and are forced to twist and turn to find sunlight will have some very interesting grain patterns.

Whatever wood grain or texture you encounter, I have the woodturning tools that will make your turnings come to life.

Thursday, February 9, 2017

Does Your Vacuum Chuck Leave Marks on Your Bowls?

I recently turned a Maple Bowl, when I mounted the bowl on the Vacuum Chuck and turned the bottom of the bowl, the vacuum chuck left a circular mark in the bottom of the bowl.  Needless to say I was very disappointed and started looking for a fix, below is a solution.


 This is the 6" Vacuum Chuck that I used on the Maple Bowl; the bowl is about 13 inches in diameter.  Notice the hard plastic between the two o-rings, that is what leaves the mark.  Larger Diameter o-rings might help the problem, but they will compress to seal  the vacuum chuck to the bowl and the hard center will be in contact with the bowl.




Enlarge the picture and you can see the mark left by the vacuum chuck, just above the blue tape

 This is Neoprene gasket material, it is about 1/16 inches thick. This material is fairly stiff but soft and flexible enough to seal
Neoprene gasket cut out of the sheet.
 Glue the gasket to the Vacuum Chuck.  I used contact cement in three or four locations on the hard center.  Avoid any large buildups of glue or debris under or on the gasket as this will not allow the gasket to seal.
 Gasket glued to the chuck and under vacuum.  Used a piece of heavy plastic so I would be able to see how the gasket reacted under vacuum.
 Vacuum gauge at 27 inches of vacuum.  This is the same amount of vacuum without the gasket.  I mounted a bowl on the vacuum chuck with the gasket and the chuck left no marks.

I think my gauge is off a little bit, it should read close to 30 inches of vacuum, because I am near sea level.
Here is the whole setup.  I purchased the parts from different suppliers and built the vacuum chucking system myself, saved a about $250.