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Techniques #1: Cutting 135 degree dovetails

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Blog entry by Dave Polaschek posted 05-02-2018 11:33 PM 1896 reads 0 times favorited 9 comments Add to Favorites Watch
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I couldn’t find anyone describing how to cut dovetails for non-square corners, so I decided to write this up. This trick will work for any angle dovetails, but you’ll have to change up the workholding jigs.

This is a description of how to cut dovetails for a 135 degree corner. This is the angle used on an octagonal box (if all the angles are equal). They’re not perfect, and there’s probably a better way to do it, but this is the best I found.

My first try cutting 135 degree dovetails used no special workholding. I just threw the pieces in the vise and started cutting. I cut tails first and I cut them pretty much as normal, except with the end of the board at a 45 degree angle, so they were pretty easy.

The pins were fairly straight too. This is feeling easy!

But the fit left something to be desired.

So I sat and thought for a bit and decided that maybe I could use a square piece in the corner, all tails, and put pins on the edge pieces that would go into it, and then cut the 45 degree angle afterwards. It couldn’t be any worse than the previous attempt, could it?

Well, that worked okay, and I might end up trying that method again, but I’ll have to think harder about the grain direction in that corner piece when I do.

So I tried again. Third time’s the charm, right?

I cut the tails square this time, just like you would on a normal dovetail. I even gang-cut them two at a time.

Then I cut the pins on a board with the end angled 45 degrees using a jig I made for the purpose. I made the 45 degree end on the board using a miter jack before cutting.

Those came out pretty good I think. They’re a little gappy where I went astray with the coping saw while cutting out the waste, but they glued up solid.

Hopefully someone else will learn from this and find it useful. To get the boards to look good in the corner, just make the corner piece (the walnut in the above photo) 0.7 times as thick as the edge piece (the ash). The example I show has the walnut thicker, and the corner looks kinda goofy to my eye.

-- Dave - Minneapolis



9 comments so far

View ralbuck's profile

ralbuck

6062 posts in 2688 days


#1 posted 05-03-2018 12:30 AM

They look good to me.

-- Wood rescue is good for the environment and me! just rjR

View Oldtool's profile

Oldtool

2779 posts in 2612 days


#2 posted 05-03-2018 01:26 AM

I think I’m confused here, still trying to wrap my head around this, but seem to be going crossed eyed.
Anyway, whatever works for you is the correct solution. Nice work.

-- "I am a firm believer in the people. If given the truth, they can be depended upon to meet any national crisis. The point is to bring them the real facts." - Abraham Lincoln

View doubleDD's profile

doubleDD

8460 posts in 2465 days


#3 posted 05-03-2018 01:59 AM

You’ve been busy figuring out simpler solutions. Very interesting.

-- Dave, Downers Grove, Il. -------- When you run out of ideas, start building your dreams.

View Timmy2Hands's profile

Timmy2Hands

193 posts in 1386 days


#4 posted 05-03-2018 02:08 AM

Matt Cremona did some good videos for a Six sided dovetailed box.

His first video is a demonstration without him talking, it was an announcement for his second child.
Here is the video link

He did a follow-up video describing how he attacked the problem.
Here is a video link for that.

Hope it helps.

-- Tim

View Dave Polaschek's profile

Dave Polaschek

3885 posts in 1004 days


#5 posted 05-03-2018 07:44 AM

Thanks, Tim! Yeah, I ended up doing sort of half-blind dovetails. Or something. Only one side of the joint shows the joinery. Which worked for the box I made.

Matt’s solution is like what I tried first, but I couldn’t get the joint very solid that way at 135 degrees. Maybe it would’ve worked better at 120 degrees for a hexagon. I’ll probably play with it more, but my google-fu was failing me and I couldn’t find anyone who had dovetailed not right-angle corners.

-- Dave - Minneapolis

View Kelster58's profile

Kelster58

755 posts in 962 days


#6 posted 05-03-2018 11:23 PM

Pretty cool Dave. Looks like a lot of work. You are a very patient person!!!

-- K. Stone “Tell me and I forget, teach me and I may remember, involve me and I learn.” ― Benjamin Franklin

View Dave Polaschek's profile

Dave Polaschek

3885 posts in 1004 days


#7 posted 05-04-2018 01:10 AM

Took longer to figure out than to actually cut them, Kelly. Thanks!

-- Dave - Minneapolis

View Jimintomahawak's profile

Jimintomahawak

73 posts in 897 days


#8 posted 05-05-2018 11:22 AM

Nice work, I really know what you mean about figuring it out. Then cutting is done in no time. I like how you used mirror to get both views.

-- Laziness drives creative thinking...

View Dave Polaschek's profile

Dave Polaschek

3885 posts in 1004 days


#9 posted 05-05-2018 11:42 AM

Thanks, Jim. Yeah, I use the mirror when cutting them anyhow, so it’s right there. I need to remember to use it more when doing project shots, too.

-- Dave - Minneapolis

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