How to make "Complementary" Segments with a wedgieless sled?

Jim Grieco

PRO Member
Hello! I just was watching the 3 videos of Jerry Bennett. In the second video, he created what he called complimentary segments by setting the wedgie sled off-center.
I use a wedgieless sled so I am not sure how to do this. The sled I use have various angles locked in by using a pin. The sled is marked for each angle using the number of segments you want to make. i.e. 12, 16, 24, etc.
How would I make these "complimentary" segments using my sled?

Thank you
Jim
 

mfisher

Super Moderator
Staff member
Hi Jim.
- I take it your sled has two fences and the fences are preset square to the blade.
You stated the fence is locked down with a pin. So there is no way to move the fence off center.

- I would make a wedgie sled like one of the vids on Bennett's site shows how to build.
 

Jim Grieco

PRO Member
Hi Jim.
- I take it your sled has two fences and the fences are preset square to the blade.
You stated the fence is locked down with a pin. So there is no way to move the fence off center.

- I would make a wedgie sled like one of the vids on Bennett's site shows how to build.
Yea I was hoping I didn't need to do this. The reason for the sled I have is to not have to buy the wedgies.
 

mfisher

Super Moderator
Staff member
Yea I was hoping I didn't need to do this. The reason for the sled I have is to not have to buy the wedgies.

I have used a digital protractor to set the fences. There is an error rate of .1 to .3% depending on the make. I used one with a 18" arm.
With a little tweaking of the fences, I could cut 12 segment rings with no problems. Once set, you could lock the fences down.

Y
 

Greg Just

New Member
The genius behind the wedgie sled is that it eliminates error. As long as you build it correctly with parallel fences and set the angle between them correctly, it doesn’t matter if the cut angles are exactly the same. You must flip every other piece to eliminate the error. I’ve had great success with Jerry’s sled. While the wedges are not inexpensive, they are worth the investment. Look for someone with a CNC machine and see if they’ll make you the angles you need.
 

Glenn McCarron

PRO Member
The genius behind the wedgie sled is that it eliminates error. As long as you build it correctly with parallel fences and set the angle between them correctly, it doesn’t matter if the cut angles are exactly the same. You must flip every other piece to eliminate the error. I’ve had great success with Jerry’s sled. While the wedges are not inexpensive, they are worth the investment. Look for someone with a CNC machine and see if they’ll make you the angles you need.
Greg, please correct me if I am wrong but I disagree that you have to flip every other piece to eliminate the error. If you draw a line along the top front of your board your cutting, the line will alternate from the front of a segment to back of the segment. Your line will always be on top of each segment. This way you end up gluing pieces together that come from each side of your saw blade. These are the complimentary angles that Jerry talks about in his video.
 

mfisher

Super Moderator
Staff member
Hi Glenn:
I was a bit confused with what Greg posted. I eventually took his flipping was directed at when putting the segments together in a ring.
Where the line is alternated between in and out when putting the ring together.
You are correct that the stock is not flipped when using the two fences.

segeasy segments.jpg
 

Greg Just

New Member
Greg, please correct me if I am wrong but I disagree that you have to flip every other piece to eliminate the error. If you draw a line along the top front of your board your cutting, the line will alternate from the front of a segment to back of the segment. Your line will always be on top of each segment. This way you end up gluing pieces together that come from each side of your saw blade. These are the complimentary angles that Jerry talks about in his video.
 

Lloyd Johnson

Administrator
Staff member
Hello! I just was watching the 3 videos of Jerry Bennett. In the second video, he created what he called complimentary segments by setting the wedgie sled off-center.
I use a wedgieless sled so I am not sure how to do this. The sled I use have various angles locked in by using a pin. The sled is marked for each angle using the number of segments you want to make. i.e. 12, 16, 24, etc.
How would I make these "complimentary" segments using my sled?

Thank you
Jim
The complimentary angle is what you get from the 2nd cut of a wedgie sled. ALL sleds, whether a wedgie or single–fence sled have multiple errors - the blade isn’t exactly 90 degrees from the table, the angle is perfect, the fence(s) are not oriented correctly to the blade, etc. When you make your first cut on a wedgie sled, all of those errors exist. When you put a perfect wedge between the two fences of a wedgie sled and make the second cut, all of the errors are multiplied by a minus 1 which means that one edge of the segment has complimentary angles to the opposite edge. When you glue two of these imperfect segments together, the complimentary angles zero out the errors. If you make a ring of these segments, every joint is corrected by the complimentary angles and you will have a perfect ring, even though none of the segments are perfect.

It is not possible to duplicate this functionality with a single-fence sled.

There is a simple way to make a template for making your own wedge, though. If you have Woodturner PRO, make a ring of the desired number of segments. Adjust the diameters so that the outside diameter is about 20” and the inside diameter is about 10”. Switch to the Segment View and if the image completely shows on your screen, you can print it to a laser printer and use adhesive spray to glue it to a thin piece of plywood or MDF or plastic and sand it to the lines. If it doesn’t fit your screen or the print preview, adjust the diameters until it displays completely.

The Segment View gives you three dimensions that you can use to verify the accuracy of yo ur sanding: the width of the wedge and the width of the large SEL and the opposing small SEL. If all three of these measurements match the calculations on the Segment View page, it is a perfect wedge.

It isn’t necessary that the entire lengths of the angled edges of the wedge be sanded correctly. If just the last 1/4” of each of the two angled edges are correct, you can rough saw the remainder of those edges as long as the are all narrower than the lines. This will still allow the wedge to separate the two fences accurately.
 
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