5 cut test

[niki]

Good day

You can read about the "5 cut test" here, but without pics

http://benchmark.20m.com/articles/TheFiveSidedCut/TheFiveSidedCut.html

You can use this method to check the sliding table or the crosscut sled.

I made it for my crosscut sled and got an "off square" of 1/128" (0.2 mm) on a length of 78" (1,980 mm) and left it like that.

I preferred to make it a thread so if somebody will "Search" for it one day, it will be easy to find.

Regards
niki

[niki]

[niki]

[drumpriest]

I see how this test will give you a very accurate understanding of how off you are, but how do you translate that into fixing the issue?

[niki]

Hi Keith

All the idea is that the error is multiplied by 4 so it's more "visible".

If the "far end" (far from you) is wider than the "near end" (near to you), as in my case on the last two pics, then, the angle between the sled fence, and the blade, is LESS than 90°.

If the "far end" is narrower then the "near end" than the angle is MORE than 90°

You have to correct by 1/4 of the difference between both ends.
For example: if the difference between the ends is 1/4", you have to move the sled fence by 1/16" to correct the problem.

Hope it's clear (with my poor English...)
niki

[final_t]

If I remember correctly, Kirby or Loren has/had this in the PDF archives on here, somewhere. I don't know if they still exist after the re-org of the software; I know I have them at home, somewhere.
Like the pics, they help!

[lcm1947]

Thanks for posting Niki. It'll be good to have this handy to look at when somebody needs it. I actually was wanting to review this procedure several weeks ago but couldn't find it so just kind of forgot about it until this post. I think I'll remember it now but down the road from now I'll probably forget and need to look it up again so naming it properly will be a very good idea and I wish everybody would do that. It sure would make the search a heck of a lot easier for everybody. There has been dozens and dozens of times I just flat couldn't find stuff I wanted to look up.

[gjat]

I see how this test will give you a very accurate understanding of how off you are, but how do you translate that into fixing the issue?

In the link niki posted, the following is the instructions to fix the issue.

Make another cut in this position (this is the fifth cut) and save the off cut.


6. Take THIS off cut and mark one end F for forward (this edge was cut first by the blade), and A for aft in the correct positions.

7. Compare the difference in width between the F and A ends; the difference IS the accuracy. For example if one end is 1/8" thicker than the other then the fence is out of square by an amount of about 1/8" over the sum of the sides that were cut. If a ~24" square test piece was used, the fence is out of square by 1/8" over 96" in length (24 x 4 = 96). The method creates an additive error each time the stock is rotated and cut.

You can use this information to determine how much to move the fence to bring the cut more into square. In the case of a 24" square test piece, the fence would be moved about 0.03" measured at a point on the fence 24" away from the blade (1/8" divided by 4 is about 0.03").

Once the new reference is set, the five sided cut test should be performed again to see how close to square the system is with a new correction. It must be understood that at some point in the alignment process it becomes a waste of time trying to dial out a small error, it is an exercise in futility. This is because of the nature of wood to begin with (which changes shape based on its environment), the basic accuracy of machines and blades, the problems in creating a repeatable setup, and trying to reliably measure such small differences in width.