# 45 Deg Miter joint for a bookcase? Possible?



## SMG (Jun 8, 2021)

Hi All, new to the forum with little furniture building experience. I'm planning my first simple furniture build - a bookcase- and would like to use 45 deg. miter joints with no screws for aesthetics. I'm concerned about strength - I would like suggestions for a simple miter joint I can handle - I have a pretty decent Delta contractors saw with cross cut and miter sleds as well as a dado blade. I think I can do a simple spline joint such as this - armed with many hours of Youtube videos  Any other miter joints that are suitable for beginners ? 









For added overall strength, I plan to beef up the back with at least a 3/8"-1/2" thick plywood. I'm sure there are other details I'm leaving out - Please let me know. Thanks.


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## epicfail48 (Mar 27, 2014)

A splined miter will be the simplest way to accomplish that particular desire. Honestly, there arent many ways to reinforce miter joints. Splines are one of the stronger ones, but you could also use biscuits, dowels, dominos, dovetail keys, or one of thoe fancy lock miter router bits. Splined joint is one of the easier to accomplish


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## sunnybob (Sep 3, 2016)

The picture you show is a vertical joint. downwards pressure is not an issue. If that joint is horizontal you need to seriously consider the weight of the books on the shelves that are going to be trying to force those joints apart, day in day out.

If what you think is a good idea but you cant find anyone else doing it, it is usually a bad idea.
A minimal outlay to achieve a strong joint is pocket screws.


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## monkey paw (Apr 15, 2021)

I personally would use a different type of joint for the corners. Then trim the face of the bookshelf with miter joints to achieve the look.


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## Bob Bengal (Jan 2, 2021)

I've used that type of spline joint to make a 6 sided column for spiral cat stairs, it worked well.

I haven't made book shelves, or much other human furniture. Will the back of the book case be against a wall or will it be seen? A much easier joint to make with the tools you have is:









(Yes my Paint skills are horrible, but you get the idea, I hope lol.)


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## FrankC (Aug 24, 2012)

If this is for top and bottom to sides the splined joint will work just fine, dado the back of the top, bottom and uprights for the back to sit into and you should have a solid carcass. Depending on the height you may want a solid shelf dadoed into the sides half way up.


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## SMG (Jun 8, 2021)

FrankC said:


> If this is for top and bottom to sides the splined joint will work just fine, dado the back of the top, bottom and uprights for the back to sit into and you should have a solid carcass. Depending on the height you may want a solid shelf dadoed into the sides half way up.


 Thanks, thats exactly what I had in mind. I'm planning adjustable shelves with one fixed shelf in the middle. I think a 1/4" thick ply is common as the back, but I can use 3/8" or 1/2" for rigidity. Only it'll make the unit a lot heavier


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## FrankC (Aug 24, 2012)

1/4" for back is fine, it just keeps the case from racking, fasten it to fixed shelf as well as sides.


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## woodnthings (Jan 24, 2009)

SMG said:


> Hi All, new to the forum with little furniture building experience. I'm planning my first simple furniture build - a bookcase- and would like to use 45 deg. miter joints with no screws for aesthetics. I'm concerned about strength - I would like suggestions for a simple miter joint I can handle - I have a pretty decent Delta contractors saw with cross cut and miter sleds as well as a dado blade. I think I can do a simple spline joint such as this - armed with many hours of Youtube videos  Any other miter joints that are suitable for beginners ?
> View attachment 428291
> 
> 
> For added overall strength, I plan to beef up the back with at least a 3/8"-1/2" thick plywood. I'm sure there are other details I'm leaving out - Please let me know. Thanks.


The 45 degree miter joints for the sides to bottom and top joint sound easy to make, but they are not! 
Here's why.... to make the miter it requires registering the opposite edge against the fence or using a miter gauge with an extended fence. Any deviation from "perfect registration" will result in a small gaps in the miter. How do I know? I've done it enough times to get some experience. Fortunately for me, I have a extremely wide table saw, so I have great support and I have enough width for most panels ..... with the exception being the sides. The sides are too long to fit between the blade and the fence, so you must use the miter gauge. A circular saw and a crosscut guide would also work, but I've never tried a 45 degree miter that way that I recall.
If you can get "decent" miters then using splines is the best way to strengthen them. There is only one issue with a long grain spline cut from the length of the board. It will easily split along it's length following the grain if too much force is applied. How much is too much force? You may find out accidentally! 
Finally, a 1/4" thick plywood back set into a 3/8" X 5/16" deep rabbet will be great and prevent the dreaded "rack and fold" like a cardboard box. Certainly the splines will be much better than nothing, but if you can make them from end grain strips, that would be so much better.


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## SMG (Jun 8, 2021)

Woodrhings, yes I was planning to use my Dubby cross sled. Registering the opposite end 5 ft away won’t be accurate or practical. 

I’m fairly new to woodworking, need to process and understand exactly what is meant by using the spline strips from end grain. I think you mean take the strip from the long edge of the panel along the grain ?


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## woodnthings (Jan 24, 2009)

SMG said:


> Woodrhings, yes I was planning to use my Dubby cross sled. Registering the opposite end 5 ft away won’t be accurate or practical.
> 
> I’m fairly new to woodworking, need to process and understand exactly what is meant by using the spline strips from end grain. I think you mean take the strip from the long edge of the panel along the grain ?


Nope. The 1/8" thick strip ripped off along the length of a board has long grain. The crosscut off an end will have end grain. If you crosscut a 1" X 12" X 3/4" off the end of that board, set the fence to rip off an 1/8" wide strip, then your strip will have the grain running across the length, not down it.


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## SMG (Jun 8, 2021)

OK I think I understand the end and Long grain, thanks for explaining. Since in a miter joints the forces will be along the width of the spline, it’s not clear to me which grain would be stronger. Maybe no difference?


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## Bob Bengal (Jan 2, 2021)

You want the grain of the spline to go from one piece to the other. For your bookcase from the side piece to the top piece. A little blurry but you can see it in the image you posted at the beginning of this thread, see what I mean? The wrong way is if the spline grain ran from the front of the case to the back, if stressed it is far easier for the spline to split.

I highly recommend making something with splined miters on a smaller scale first, both to learn the required accuracy and what it is like to assemble it. Something with a rectangle say 1' by 2'. I've only been woodworking 3 years, somethings I've done a lot of, but something I'm a raw beginner at is crosscutting a long piece on a table saw, it can be tricky for both safety and accuracy. That it will be a bevel doesn't make it easier. Before committing to the book case design get some inexpensive wood and experiment with making that cut on a long piece.


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## Bob Bengal (Jan 2, 2021)

Also experiment with making the dado cuts at the end of long pieces. Ask on the forum how to do that and the crosscuts at the end of long pieces, I'd like to hear what the more experienced members have to say too.


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## rogerh (Sep 13, 2020)

I built a set of three cabinets, all had miter joints. I used four biscuits in each joint. I also used, three home made strap clamp on each cabinet. I used red oak.


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## SMG (Jun 8, 2021)

Thanks Bob Bengal for clarifying - makes sense. I'll be practicing with some cuts soon. 

rogerh - thats a nice looking cabinet 👍🏼. What kind of joint did you use at the mitered ends?


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## rogerh (Sep 13, 2020)

SMG said:


> Thanks Bob Bengal for clarifying - makes sense. I'll be practicing with some cuts soon.
> 
> rogerh - thats a nice looking cabinet 👍🏼. What kind of joint did you use at the mitered ends?


I used a miter joint with 4 biscuits in each joint.


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