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Wedgie sled calculations

Shawn Schiebrel

PRO Member
Hello, I originally started this in the software support forum, but I think this is a better place for it.
I use a wedgie sled, but I'm having an issue with conversions. All of the calculators that I've seen ( Woodturner pro is my fav ) have the angle for a single fenced sled. All well and good, but when using a wedgie, the angle posted is half of what you need ( otherwise you cut double the number of segments ). No problem, we just double the angle number and use that. I don't use the wedgie templates, I just use a digital protractor like a wedgie piece... works great.

In all the videos the only thing that is demonstrated is how accurately the rings go together, and by god, they do.. great work there. but I haven't seen anyone speak to the segment length and how it's measured... are you measuring from the blade to the stop using the fence angles? which fence? or from the blade to the stop, 90 degrees from the blade?

Since I'm using a greater angle than is listed on the calculator, my segment length is different. So without actually sacrificing wood doing testing, does anyone know if the angle is the only thing that would be different or can I not trust any of the numbers?
I replied to your other post but I didn't completely understand your question but you gave a better explanation here.

First, ALL of my calculations are correct. After 16 years, they better be. :) The segment edge length is calculated based on the number of segments and the diameter of the ring. It doesn't matter if you cut the segments traditionally, with a wedgie sled or with a butter knife, the segment edge length calculation is what it must be after it has been cut.

Setting a stop for a wedgie sled is a weakness of the design in that the wood is unsupported on the cutoff side of the blade and therefore does not make it easy to set a fence. I do set a stop, though, that is separate from the sled and it works fine.

With regards to a digital protractor, if you don't use a perfect wedge, you defeat the purpose of the sled and it is no better than a traditional sled. I use a digital protractor all the time snd it is accurate to +/- .1 degrees. This will result in more than a 1 degree gap in 12 segments. Using a perfect wedge takes away that gap ever time.

In my other post, I talk about what I do to make my own wedges.

in my testing, i had no problems using a protractor and all my rings have no gaps, perhaps i just have a very accurate one. In any case, my question is this. I tested my sled using the calculations for an 8 segment ring, I know we discussed this in the other thread but for those here that want the background here it is. the calculator says an 8 segment ring miter angle is 22.5 degrees. I set the angle between the 2 fences at 22.5 degrees and ended up with 16 segments. Easy enough to fix, just double the angle. but I was thinking too that the segment edge length is 4 5/32" for an 8 segment ring that's 10" in diameter could be wrong. my question comes here, since this length is based on specific angle and presumably, a specific method of measuring and cutting. if I double the angle to get the number of segments to work out. the measurement between the stop ( which is a separate stop in the other slot ) is vastly different if you measure along the fences angle using 22.5 ( the original calc output ) vs 45 degrees ( the now doubled angle to get the number of segments to come out right ). you didn't state how you measure the segment edge length. if the measurement is strait across ( 90 degrees ) from the blade to the stop, then it doesn't make a difference. but if the 4 5/32" is the measured using the angle of the fence from the blade to the stop, then it's a big difference and confusing, since both fences are relative to each other and don't have any specific relationship to the stop. i'm assuming, since the calc says use 22.5 degrees and measure such and such amount, then that 4 5/32" is going to be wrong using a wedgie sled since that measurement is assumed to be using the 22.5 degrees referenced to the blade and using that angle across the blade to the stop and will always be consistent. I hope you understand, it's difficult to get this across without drawings. in fact, sitting here visualizing the issue, i see that i'm making it too difficult. if you draw a line 90 degrees to the blade, across the sled left to right, then the 22.5 degrees the calc is spitting out is referenced to this line and makes sense why you need to double the angle ( 22.5 from line down and another 22.5 from the line above ) so if you make the wedgie as even as possible ( from a half above the middle and half below ) then the segment length measurement comes out fine. if you didn't want to do this, to take advantage of the somewhat funky nature of the skewed nature of primary/complementary cuts, then you could still make the measurement work by setting the original angle ( say 22.5 degrees ) to the blade, measuring and setting your stop, then setting the fence angles with the wedgies.
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I do understand.

The segments you cut with a traditional sled or a wedgie sled will be identical. With a miter gauge set at 22.5 degrees, if you use your digital protractor to measure the angle of the segment, it will be 45 degrees. If you put a 45 degree wedge in a wedgie sled, it will also make a segment that is 45 degrees. The mat here is simple - there are 360 degrees in a circle. Divided by the number of segments (8), each segment must be exactly 45 degrees or you will have a gap. So if the segment edge length is identical regardless of the sled, the resulting diameter of the rings will be identical.

The part you are missing is that you are also cutting your segments at 22.5 degrees because the wood is at a 22.5 degree angle to the blade at both of the cutting positions. The two sleds are just two different ways to cut an identical segment. This is true for however many segments you cut to make a segmented ring.

There are two things that always hung me up when I started- the cutting angle and segment length. The cut angle (22.5) is always measured for one end of the segment. As Lloyd said, when both ends are cut, the total angle (45) will result in eight pieces for the ring. For me, it is easier to divide 180 degrees by the segment count. This gives me the cut angle for one end.

Segment length is measured on the long side of the segment following the angle of the cut - not perpendicular to the blade. I can't tell you how many multi-generational laminations I have ruined by screwing this up.