# How to make a strong non-90 miter joint?



## ChiknNutz

I am looking for some advice on how to make a strong joint that is essentially a miter joint, but the joints are NOT at 90 degrees to each other. The overall shape is a trapezpoid box (one side longer than the other, sides same length but opposite) and the angles are about 9 or 10 degrees off of 90. This is essentially what I am thinking a dovetail would be good for, but given the application, this seems like a lot of effort to go to and the complexity the non-90 degree angles add. I've looked at some alternatives like box joints and splined joints. I do NOT want a screwed-together joint. A splined joint, either hidden or visible, seems like it might work but am not sure. So what are my options here? Thanks!


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## woodchux

Other strong miter joint options are dowel pins and domino "biscuit" joinery, but be certain the cut angles are smooth & tight WITHOUT gaps to each other. Be safe.


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## epicfail48

A spline would probably the best way to go, as far as effort/performance is concerned. Doweling would be stronger, but drilling the holes for the dowels at the end of an angled workpiece could be tricky. Biscuits would likely work as well as a spline would, but that requires having a biscuit jointer


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## ChiknNutz

Similar to the domino joint, could this also be accomplished with a loose tenon M&T? The angle is what I am still concerned about as it just complicates things.


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## woodnthings

*The issue is certainly the "odd" angles*

If you search segmented bowls you'll find various angles for mitered joints, however there may not be an 80 degree example.... I donno?

You can make splined miters down the bevel angle using the tilt feature on your table saw. This makes a strong joint. Splined frames are different than splined bevels which are what to look for.

https://www.youtube.com/watch?v=tr402Nvfhs0

If you make your spline stock the same dimension as the kerf of your blade that will be all you need for the spline. A digital protractor would be helpful in setting the bevel angle. If the angles are all different on the corners you will have "fun" figuring out how to arrive at the proper setting.... :no:


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## Toolman50

I would use my biscuit joiner. It's completely adjustable to cut at angles.


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## Al B Thayer

https://m.youtube.com/watch?v=JuyRxbqFjdg

Al


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## woodnthings

*when is a miter a bevel?*

The question is relevant because the techniques for splining are different. A picture frame has mitered corners. A cabinet has mitered bevels, kinda of redundant...


The cabinet or box joint:












A splined mitered corner like on a picture frame:










Both slots can be made on the table saw, but the picture frame must be held vertically so the kerf is in the edge, not on it's flat face. The kerf in the cabinet pieces is made with the blade at 45 degrees. A router with a slot cutter can be used on the picture frame, but the table saw is best for the cabinet or box pieces.

When is the cut a miter? In my experience it's when the long face is flat on the table and the cut is a 45 degree crosscut, the blade set at 90 degrees. When making a bevel, the large flat surface of the stock is flat on the table and the blade is set at a 45 degree bevel angle. Some folks use the terms interchangeably, but that can add to some confusion.


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## Al B Thayer

I never put two pieces of wood together with a bevel. But I do bevel the edges to make them look better.

Al


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## FrankC

I believe a miter joint is made by beveling each of two parts to be joined, JMHO.


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## Wyo7200

You probably already know this, but I'd suggest using masking tape to apply pressure during the glue up.


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## Al B Thayer

I use masking tape on miter/bevel joints. If you need any more pressure something's wrong.

Al


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## ChiknNutz

Al B Thayer said:


> https://m.youtube.com/watch?v=JuyRxbqFjdg
> 
> Al


Yes, but perhaps I missed it showing how to accommodate a non-perpendicular joint. In this particular application the joint does not need to be beveled/mitered, but could be a butt joint whereby a M&T could be employed. The hurdle I am trying to overcome is the non 90-degree joint.


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## Oneal-Woodworking

ChiknNutz said:


> Yes, but perhaps I missed it showing how to accommodate a non-perpendicular joint. In this particular application the joint does not need to be beveled/mitered, but could be a butt joint whereby a M&T could be employed. The hurdle I am trying to overcome is the non 90-degree joint.


 
A spline (or biscuits) would be easiest and all you really 'need' is a table saw to cut the pocket with. 

Cut your angles like you normally would and once everything fits the way you want it - Cut the grooves for your spline or biscuits. 

Normally I cut biscuit pockets either on the shaper or on the router table with a slot cutting bit. Ten times more accurate than the Biscuit Joiner tools that are handheld...


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## Al B Thayer

ChiknNutz said:


> Yes, but perhaps I missed it showing how to accommodate a non-perpendicular joint. In this particular application the joint does not need to be beveled/mitered, but could be a butt joint whereby a M&T could be employed. The hurdle I am trying to overcome is the non 90-degree joint.



You can cut any angle within reason with my fixture. See it's my design and it works so well I like sharing it with everyone. Which includes 30 different countries and countless copies sent out.

Al


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## Toolman50

You can make this miter type joint stronger with a spline which has been previously suggested or put two dowels through each joint after it has been assembled. I don't know what the project is, but you could also use 
two screws at each joint or use a half lap-miter which will be very strong. 
What are you making?


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## ChiknNutz

I already finished the project I intended this for using screws and flush plugs but plan to use this joint more in the future and would like to come up with a more traditional joint (M&T, spline, etc).

Sent from my iPhone using Wood Forum


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## GeorgeC

epicfail48 said:


> A spline would probably the best way to go, as far as effort/performance is concerned. Doweling would be stronger, but drilling the holes for the dowels at the end of an angled workpiece could be tricky. Biscuits would likely work as well as a spline would, but that requires having a biscuit jointer


Can also be done with a router.

George


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## ChiknNutz

Here is a better representation of the overall design. The pieces are essentially based on a dimensional 2x6. My plan was to use a loose M&T joint, but as I've said, the angle of the joint is what has be confused on how to actually make it other than with a Festool Domino (I am not aware of any commercial knock-offs to the Domino). I do understand that a biscuit joiner would work, but am not convinced that a biscuit joint provides the desired joint strength. A custom, purpose-built jig based on a router is what comes to mind, that incorporates an angled baseplate or fixture of some sort.


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## Toolman50

ChiknNutz said:


> Here is a better representation of the overall design. The pieces are essentially based on a dimensional 2x6. My plan was to use a loose M&T joint, but as I've said, the angle of the joint is what has be confused on how to actually make it other than with a Festool Domino (I am not aware of any commercial knock-offs to the Domino). I do understand that a biscuit joiner would work, but am not convinced that a biscuit joint provides the desired joint strength. A custom, purpose-built jig based on a router is what comes to mind, that incorporates an angled baseplate or fixture of some sort.


Good pictures, but what is it?


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## ChiknNutz

Half of the base to a table. There is also a center stretcher, but the point of this thread is for the corner joints. To see the finished product, go to this post: http://www.woodworkingtalk.com/f13/cedar-slab-table-101786/


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## woodnthings

*very nice illustrations*

You are fighting physics here by wanting the joint to be structural. It's like any rectangle, or picture frame or box without a back, the joints have to carry all the loads, and they are usually not sufficient.

If this object is subjected to any lateral forces, it will fail in the joinery. A welded steel structure would be much better, but wood just doesn't have those characteristics.
If you can add a back, most of those issues will disappear, but we don't know what the object is or does or what loads it is subjected to.....or what it's orientation is in relationship to side loads... does it lay flat or upright as shown?


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## ChiknNutz

woodnthings said:


> Y...but we don't know what the object is or does or what loads it is subjected to.....or what it's orientation is in relationship to side loads... does it lay flat or upright as shown?


Please refer to the post I referenced which shows the application. It works fine in it's current state, but I would still prefer to be able to produce a better joint for future applications.

I don't see why this joint could not be a very strong joint when coupled with a M&T. You get the benefit of the glue bond plus add'l shear capability offered by the tenon.


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## NickB

Looks like it would be pretty easy to drop an angled spacer into a dovetail jig and go to town...


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## woodnthings

*I can see your reasoning*

That's a very clean looking design for a table. In my opinion you are just asking a lot of the joinery, as I stated above. That design lends itself to welded metal far better than wood, again my opinion based on considerable experience in both woodworking and welding metal.



All you can do is use the best methods for wood joinery, they are really no different on an 90 degree angle or 80 degree, or what ever you have. Finger joints offer a lot of surface area, a mortise and tenon on an angle will be tricky to make without a special router jig, or a tilt table hollow chisel mortiser...$$$. You are still relying on slender wood components and a glue bond. You could upsize the components for more strength,but then you lose the clean design... a quandry for sure.


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## ChiknNutz

Perhaps a "splayed" dovetail joint is more appropriate. I don't own a DT jig, have only done a few and prefer to do them by hand anyway.


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## Al B Thayer

ChiknNutz said:


> Here is a better representation of the overall design. The pieces are essentially based on a dimensional 2x6. My plan was to use a loose M&T joint, but as I've said, the angle of the joint is what has be confused on how to actually make it other than with a Festool Domino (I am not aware of any commercial knock-offs to the Domino). I do understand that a biscuit joiner would work, but am not convinced that a biscuit joint provides the desired joint strength. A custom, purpose-built jig based on a router is what comes to mind, that incorporates an angled baseplate or fixture of some sort.



Exactly the type of joint my machine shines on. All you have to figure out is what angle to cut the pieces at. Then you cut the mortise in each end. Same setting for each piece mating together. Insert the loose tenon and glue.

If you were to cut these by hand. The tenon on the end would have to be cut at the odd angle and would be limited on the length of the tenon.













I cut all the joints for 6 dining chairs with this machine. It would take a life time to do all these by hand.







The machine is easy to build and costs less than $45 with your router.

Al


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## ChiknNutz

Al, I have looked at the YouTube videos (all two that I could find) and am just not seeing it. Please, I am all in if this will do what I am looking for but ya gotta show me. I only see the ends being done on the flat at right angles, not at an angle like I am hoping to achieve. Can you show me some pictures of this thing in action or the end result showing some of these off-angles? What I am not seeing is any means of adjusting either the router or the workpiece to anything but 90 degrees to each other (not counting the ability to rotate the workpiece laterally along the plane of the table). I dunno, maybe I am just not clearly explaining or showing it, but I thought I did.

Also, finding your stuff is not all that easy and I am quite computer literate. You should be including links to you stuff somewhere here unless that is against the policy here.


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## Al B Thayer

ChiknNutz said:


> Al, I have looked at the YouTube videos (all two that I could find) and am just not seeing it. Please, I am all in if this will do what I am looking for but ya gotta show me. I only see the ends being done on the flat at right angles, not at an angle like I am hoping to achieve. Can you show me some pictures of this thing in action or the end result showing some of these off-angles? What I am not seeing is any means of adjusting either the router or the workpiece to anything but 90 degrees to each other (not counting the ability to rotate the workpiece laterally along the plane of the table). I dunno, maybe I am just not clearly explaining or showing it, but I thought I did.
> 
> Also, finding your stuff is not all that easy and I am quite computer literate. You should be including links to you stuff somewhere here unless that is against the policy here.



It's done the same as if you were using the Domino. Cut the pieces and fit them together. Then on the mortise machine you make a rest that holds them in place. The router cutter or bit makes the cut on the mating sides at a right angle to the surfaces being joined. You end up with the tenon at a right angle to both pieces. 

The cutting of the mortise is a matter of about 5 to 10 seconds because it's done with shallow cuts sliding between the set stops. The cut is super clean and will be very accurate. Unlike the Domino, you can use any size bit that fits the need and you don't have to buy those expensive dominos from Fe$tool. 

Al


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## MattS

Al B Thayer said:


> You can cut any angle within reason with my fixture. See it's my design and it works so well I like sharing it with everyone. Which includes 30 different countries and countless copies sent out.
> 
> Al


That is a slick fixture - do you have a website I can see the plans on?


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## Al B Thayer

MattS said:


> That is a slick fixture - do you have a website I can see the plans on?



I just have the YouTube videos. You can see all of them by searching Al B Thayer. The plans are sold on EBay.

Thanks for the kind words.

Al


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## ChiknNutz

*Still not getting it...*

Al,

I must be dense because the light bulb still has not come on. I have a couple of related questions for you still.

1) How did you cut the mortises across the width of the chair parts in the first picture? More specifically, how do you hold those pieces? I understand the mechanics of the jig, as I have built something in a similar vein. It seems those pieces would have to stand upright from the table and I don't get how you hold them in the jig you have shown. The way I understand your jig is that all pieces would be held with their widest face down, parallel to the table top.

2) How would you cut the mortise in the noted piece as shown in my second picture, noting that the joint is at a 100 degree angle? I suppose alternatively, you could have the tenon always be perpendicular to each face, but that still doesn't resolve how to hold the workpiece at a non-90 degree angle like in the third picture.


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## woodnthings

*did you see this?*

To make the mortise at "X" angle you just clamp it against the fixture which is set to that angle. 

https://www.youtube.com/watch?v=JuyRxbqFjdg


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## Al B Thayer

ChiknNutz said:


> Al,
> 
> 
> 
> I must be dense because the light bulb still has not come on. I have a couple of related questions for you still.
> 
> 
> 
> 1) How did you cut the mortises across the width of the chair parts in the first picture? More specifically, how do you hold those pieces? I understand the mechanics of the jig, as I have built something in a similar vein. It seems those pieces would have to stand upright from the table and I don't get how you hold them in the jig you have shown. The way I understand your jig is that all pieces would be held with their widest face down, parallel to the table top.
> 
> 
> 
> 2) How would you cut the mortise in the noted piece as shown in my second picture, noting that the joint is at a 100 degree angle? I suppose alternatively, you could have the tenon always be perpendicular to each face, but that still doesn't resolve how to hold the workpiece at a non-90 degree angle like in the third picture.



The first picture cuts were made standing the part on end. Block on one side block on the back. When you do the cuts there is very little force on the part because the cut is made 1/16 at a time. But the table travels quickly back and forth. 

The second cuts were made by laying the part on the narrow end lying down. Both back legs were cut with the same setting and then just flipped so the mortise was on the outside on each side. The parts were not cut for left and right until after the mortise was cut.

Maybe I'll make some more videos with possibilities one would use to build something with. But it bugs me when you watch a video of some machine doing a joint no one uses. Panorouter man comes to mind.

Al


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## Al B Thayer

ChiknNutz said:


> Al,
> 
> 
> 
> I must be dense because the light bulb still has not come on. I have a couple of related questions for you still.
> 
> 
> 
> 1) How did you cut the mortises across the width of the chair parts in the first picture? More specifically, how do you hold those pieces? I understand the mechanics of the jig, as I have built something in a similar vein. It seems those pieces would have to stand upright from the table and I don't get how you hold them in the jig you have shown. The way I understand your jig is that all pieces would be held with their widest face down, parallel to the table top.
> 
> 
> 
> 2) How would you cut the mortise in the noted piece as shown in my second picture, noting that the joint is at a 100 degree angle? I suppose alternatively, you could have the tenon always be perpendicular to each face, but that still doesn't resolve how to hold the workpiece at a non-90 degree angle like in the third picture.



The last picture you posted is how they would be cut in the machine. The parts have the cut registered square to the bit. But after a second look it could be either way for that one.

Al


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## Rebelwork

A biscuit would work for this application. Different sizes, different applications. Domino's would work as well. Dowels would work and cheaper than Domino's. One Domino equals two dowels. As spline would work but would be seen and puts you back to a biscuit.


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## ChiknNutz

I've considered a decorative spline too.


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## Al B Thayer

ChiknNutz said:


> I've considered a decorative spline too.



You can cut those with little setup too. 

The table is very nice and the mix of live edge with that base also works well. Seeing the splines on most work isn't maybe desirable but here there really aren't any rules.

Al


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