Good Evening,
I know it has been a while since addressing this topic, but I just bought a used Grizzly G1010 4x6 and I wanted to align it before starting to use it.
I spent a LOT of time reading through this forum and
I want to compliment all of you on the excellent work you have done here.
I am specifically interested in the vertical alignment discussed here, and especially John's paper:
"Fixing vertical squareness or Worn pivot bearings on a 4x6 Bandsaw v2.pdf"
This paper is excellent, and I have discovered that my table is very smooth and flat.
But I do have an issue with the pivot not being parallel to the table (to the tune of around 1/16").
While learning about this, I made a simple CAD model shown here:
If you look at this model from the front (facing the vise wheel), it looks like this...
(you can see as the blade goes up, it remains perfectly square, always aligned with the engineer's square):
Now, if I look at the same view, but with a tilted pivot...
the blade travel moves away from the square (by around 1/8" in this illustration):
I love the way you guys have come up with to fix this by machining / filing the pivot pin.
There is one thing that bothers me however, and I would like to get your opinions...
The issue relates to the technique of using the 1x4 S4S test board to determine the necessary offset for machining.
If you look carefully at the blade path with and without an offset, you get this:
?
Notice that with the tilted pivot, the blade drifts to the side (1/8" in this example), but it is important to note that the blade itself is
always vertical.? This is because everyone (rightly so) adjusts the blade guides so the blade is vertical.? What this means is that when you are doing a test cut, the blade will want to cut vertically (as all good band saw blades do),
but it is drifting to the side because of the tilted pivot.? Doesn't this mean that the test cuts are not really correct and may tend to be curved or otherwise inaccurate?
It seems to me that it might be better to not use test cuts because of this effect, and rather, just measure the gap between the blade and the engineer's square over a 5" distance (which corresponds to the pivot bearing spacing).? This measurement seems more direct, simpler and is not subject to any error from a blade that is being forced sideways by the tilted pivot during the test cut(s).
When I try to correct this I will start with a new pivot shaft, and the beauty of this technique is that nothing is being modified with the saw (other than adding a grub screw) so if a mistake is made, it is easy to revert back to the original setup.
Does you agree with me that this sideways drifting has an impact on the accuracy of the test cut method of measurement?
-Tom
