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Discussion Starter #1
Have any of you built boxes with splayed sides like that shown in the attached photo? This picture shows butt joints and was taken from an online Compound Angle Calculator. I think this is the first step toward adding finger joints if you are so inclined
compound miter calc butt joint.jpg
compound miter calc butt joint.jpg . If you cut the prescribed angles on the table saw and are happy with the butt joint as show, can you do the glue up directly from the table saw or will the board with the exposed end grain have to be sanded so that it is flush with mating board. This is not related to removing small misalignment errors that invariably occur during glue up. I hope I have made this (rather subtle) question clear.
 

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Finger joints have tapered pins and are used to join boards end to end to make longer paint grade boards. Box joints have square pins and used to make strong corner joints in boxes. I think you want the box joints for your project and not finger joints.

If you cut the box joints in the ends of your boards at 90 degrees to the angled board end this is one of the angles of your tapered box compound joint, and with the board tilted back by the other angle of the compound joint as you cut the box joints you will have the other angle of your compound joint and both boards should fit together. You may need slightly longer box joint pins so the excess can be trimmed off later after the joint is glued together, because the joint is going together at an angle other than 90 deg. the joint overlap of the two boards will result in more of the pin side surfaces being involved in the joint. The bottoms of the cuts in the box joint will be angled back (deeper) as well.

I haven't ever attempted this, but I have cut many box joints for straight sided boxes. I use an Incra I-Box jig and my Unisaw to cut them. I doubt that the I-Box jig could be modified easily to hold a board at the needed angle, but a shop made jig could be designed to do this.

The Kyrmi Mini Fence was available 20 years ago that had backers to hold the boards tilted back at common angles for doing this type of thing on a table saw, but Mr Kyrmi was in his late 80's when I last saw him back then, and he was kind of a one man business at the time, so I doubt that he or his business have survived. His video was on Youtube, but I could not locate it now. It was of very low quality compared to todays videos and provided on a VHS tape with his jig, so they likely pulled it for lack of quality and no use. His jig was very much like a typical box joint jig, but angled backers could be used to tilt the board being cut back at a desired angle while cutting the box joint. The table saw blade then cut the slot at the increasing depth in the board end.

Charley
 

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Discussion Starter #3
You are correct in that I want box joints and not finger joints. My bad. Episode 8 of season 8 (2014) of Woodsmith Shop TV program addressed the kind of joint. They also have a set of plans on how to build a silverware tray that has splayed sides and box joints. Unfortunately my test cuts in 3/8" MDF do not yield sides that have a 90 degree included angle and I have not figured out what is wrong. They (Woodsmith) used a shop built box joint jig. I have the Incra I-box jig but in making a few shop quality boxes with all 90 deg angles, I never fell in love with it as others on this forum. Instead, I have recently used my Incra router table fence to make box joints. Yes, you do need a front and back backer board but the bottom of the slots are flatter than I get with my Freud dial a width dado set. I was hoping someone on the Router Forum had some actual experience making box joints with splayed sides and would share their experiences with me.
 

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I'm not sure if this would do the job but it would do the job for me. I have been looking for years on how to make an 8 sided table with box or dovetails.
 

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I'm not sure if this would do the job but it would do the job for me. I have been looking for years on how to make an 8 sided table with box or dovetails.
Do you mean a table top that is 8 pie pieces joined by sliding dovetails? Or the part below the top is like an 8 sided box?

Last summer I made a DIY jig for normal 4 sided through dovetail boxes. Then I tried to make a jig for an 8 sided DT box, failed, I don't think routers can do the required angles and I don't have the skill or patience to do them with hand tools.

I haven't tried yet but think 6 or 8 sided box-joints can be done on a router table or TS.
 

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You are correct in that I want box joints and not finger joints. My bad. Episode 8 of season 8 (2014) of Woodsmith Shop TV program addressed the kind of joint. They also have a set of plans on how to build a silverware tray that has splayed sides and box joints. Unfortunately my test cuts in 3/8" MDF do not yield sides that have a 90 degree included angle and I have not figured out what is wrong. They (Woodsmith) used a shop built box joint jig. I have the Incra I-box jig but in making a few shop quality boxes with all 90 deg angles, I never fell in love with it as others on this forum. Instead, I have recently used my Incra router table fence to make box joints. Yes, you do need a front and back backer board but the bottom of the slots are flatter than I get with my Freud dial a width dado set. I was hoping someone on the Router Forum had some actual experience making box joints with splayed sides and would share their experiences with me.
You can use the Incra I-Box jig to make your box joints on the angled edges of your tapered box corners, but to make compound cut box joints. Your working piece will just be fitted into the jig with the angled end down flat in the jig and the rest of the work piece sitting at a sideways angle in the jig,

But this will only give you one of the angles needed for making the compound cut box joints. What is really needed is a jig that will not only cut the joint this way, but also hold your work piece angled back toward you by the second angle needed, so the inside surface of each box joint cut will be deeper than the outside surface of the work piece. This angle of the work piece has to be the other angle that you chose to make your compound cut. The I-Box jig cannot do this double angle cut.

The Kyrmi mini fence works much like a standard shop made box joint jig where you have the equal sized pin and blade width and you step your work across the face of your miter gauge to make the box joint the width of your work, but his Mini Fence also allowed you to use precision angle blocks on the face of the miter gauge that you clamped your work to so it was tilted back toward you as well as being angled to the side, so as to cut the edge of your work piece at both angles. You need both angles of your compound cut in order to make the box joints that you need. It's this tilted back angle for holding your work piece that will be the most difficult to achieve. Only a shop made jig that can hold your work piece angled in both directions to the angles needed will produce the compound angled box joints that you need for your tapered box corners.

I have the Freud SD608 Dial A Width dado blade set, but I only make large 1/2" or larger box joints with it, because the bottom of each cut made by it is not as flat as I would like for my nice tight box joints. This isn't so much of a problem and is less noticeable when making larger box joints. For 1/4 & 3/8" box joints I prefer the Freud SBOX8 blade set, and for the 1/8" box joints that I like for tiny boxes a Freud Flat Tooth Grind Ripping Blade LU87R010 that is 0.126" in tooth width and FTG in tooth shape that does quite well for these.

Charley
 

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Do you mean a table top that is 8 pie pieces joined by sliding dovetails? Or the part below the top is like an 8 sided box?

Last summer I made a DIY jig for normal 4 sided through dovetail boxes. Then I tried to make a jig for an 8 sided DT box, failed, I don't think routers can do the required angles and I don't have the skill or patience to do them with hand tools.

I haven't tried yet but think 6 or 8 sided box-joints can be done on a router table or TS.
What I was trying to do with 8 sided table was to make the apron 8 sided, much like the sample that was done in the video. The top would simply be cut to match the shape of the apron. I was trying to reproduce an antique that I had seen.
 

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Discussion Starter #9
You can use the Incra I-Box jig to make your box joints on the angled edges of your tapered box corners, but to make compound cut box joints. Your working piece will just be fitted into the jig with the angled end down flat in the jig and the rest of the work piece sitting at a sideways angle in the jig,

But this will only give you one of the angles needed for making the compound cut box joints. What is really needed is a jig that will not only cut the joint this way, but also hold your work piece angled back toward you by the second angle needed, so the inside surface of each box joint cut will be deeper than the outside surface of the work piece. This angle of the work piece has to be the other angle that you chose to make your compound cut. The I-Box jig cannot do this double angle cut.

The Kyrmi mini fence works much like a standard shop made box joint jig where you have the equal sized pin and blade width and you step your work across the face of your miter gauge to make the box joint the width of your work, but his Mini Fence also allowed you to use precision angle blocks on the face of the miter gauge that you clamped your work to so it was tilted back toward you as well as being angled to the side, so as to cut the edge of your work piece at both angles. You need both angles of your compound cut in order to make the box joints that you need. It's this tilted back angle for holding your work piece that will be the most difficult to achieve. Only a shop made jig that can hold your work piece angled in both directions to the angles needed will produce the compound angled box joints that you need for your tapered box corners.

I have the Freud SD608 Dial A Width dado blade set, but I only make large 1/2" or larger box joints with it, because the bottom of each cut made by it is not as flat as I would like for my nice tight box joints. This isn't so much of a problem and is less noticeable when making larger box joints. For 1/4 & 3/8" box joints I prefer the Freud SBOX8 blade set, and for the 1/8" box joints that I like for tiny boxes a Freud Flat Tooth Grind Ripping Blade LU87R010 that is 0.126" in tooth width and FTG in tooth shape that does quite well for these.

Charley
I saw a recent review of the Freud SBOX8 blade set and it was stated that the diameter is not consistent with the safety system on a SawStop.
 

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I saw a recent review of the Freud SBOX8 blade set and it was stated that the diameter is not consistent with the safety system on a SawStop.
I don't think it's the diameter, it has something to do with what a blade is coated with. Or at least the teeth of the blade.
 

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I don't think it's the size this is what I just found when searching which is what I had heard about certain blades. Not to mention humidity has an effect.

Can you use dado on SawStop blades?
Steel blades and dado sets with a lacquer finish or other coating on the teeth should not be used as the coating may inhibit or slow the speed at which the safety system detects skin contact. However, most coated blades do not cover the blade teeth. Those blades may be used on SawStop saws.
 

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Discussion Starter #13
I don't think it's the size this is what I just found when searching which is what I had heard about certain blades. Not to mention humidity has an effect.

Can you use dado on SawStop blades?
Steel blades and dado sets with a lacquer finish or other coating on the teeth should not be used as the coating may inhibit or slow the speed at which the safety system detects skin contact. However, most coated blades do not cover the blade teeth. Those blades may be used on SawStop saws.
I am reasonably sure it is the diameter. I have both Freud 8" dado sets and they work fine with my SawStop. I have to change my safety cartridge when I use the dado blades but do not have to make any fine adjustments to the cartridge position.
 
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