Collapsing basket

[KernelD]

Having difficulty getting the layers to open more than 1/8 in.  I enlarged the pattern to 120%.  I drilled the starter holes at 0 degrees but cut the layers at the suggested 3 degrees.  I have tried sanding inside and outside of each layer but no change to the 1/8 in.  What steps do I take to get the layers to open more?  This was a test on aspen.  Since it didn't work for me what do I do differently.  I know Carol of bowl and box fame always drills her starting holes at same angle she cuts the layers.  Will that fix the problem?  If not, do I need to change my cutting angle?  If yes, to what angle?

Respectfully,

Doug

[julief]

Thickness of the wood, size of the blade, etc. go into determining the angle.  If your basket won't open enough, you need to increase the angle - not by much.  1/2 to 1 degree should be enough to get you there.

[Rapid Roger]

I don't want to start an argument with julief but, I would do exactly the opposite.
Assuming you use the same wood, thickness and blade, I would reduce the angle. If you cut the first at 3 degrees and it won't open, I would change the angle to 2-1/2 degrees. If that is still not enough, I would go to 2 degrees. The closer you get to a 90 degree cut, the looser the segments will get.
It is all just a SWAG thing at first so experimentation is required to get a final answer to your question.

Rog

[EIEIO]

Increasing the angle will decrease the opening of the basket. Decreasing the angle or using a larger blade will increase the opening.

When cutting for inlay or an interference fit (like you want with the basket) you calculate the angle or the drop by this formula:
  sin(angle) = blade kerf/drop height = K/D. (wood thickness does not come into it).
You can reorder this so that D = K/sin(angle) or angle = inverse sin(K/D)

So if you use an FDUR#5 blade and cut at 3 degrees,
 sin(3) = 0.052; K = 0.015 (from Mike's web site for that blade); Drop D = K/sin(angle) = 0.015/0.052 =  0.286" (a little more than 1/4")

If you use a smaller blade like the FD-TC 2/0 (0.008" kerf), then D = 0.008/0.052 = 0.154" (a little more than 1/8")

So go to a thicker blade or a smaller angle to get the basket to open more. Too small an angle an you won't get it to grab. Here's a few calculated values using the FD-UR #5:
Angle          Drop
1                 0.86 (will not grab on a 3/4" blank)
2                 0.43 (may not grab on a 1/2" blank)
3                 0.29   
4                 0.22
5                 0.17

[julief]

Guys, you are totally right.  I get bassackwards sometimes. 

[EIEIO]

The angle is a little different when you consider the slope of the ring when you open the basket. If you have a 6" outside diameter, cut your spirals to be 1/4" thick, go for a rise of 1/4, 3/8, or 1/2", and use either a 0.010" Kerf or a 0.015" Kerf, the blade angles are as below.
Diameter   6      
Ring   0.25      
Kerf   0.01      
H           0.25      0.375   0.5
Angle   2.23      1.44   1.02
         
Kerf   0.015      
H           0.25       0.375   0.5
Angle   3.38       2.20   1.60

I can send you a spreadsheet if you want to fill in your own numbers.