# CNC Cut Dovetails



## Ger21

This forum seems to be pretty quiet, so I thought I'd post some pictures of what I've been working on for the last year. I've been writing a program to create g-code for cutting dovetails on a CNC Router. No additional CAD or CAM programs were used. Just enter a few parameters, export the g-code and cut.

With a CNC, you're only limited by the size of the tool. Dovetails can be any size, any width, any spacing.

Here are some samples I've been making for testing. 
In the first pic, all the pins and tails are different sizes.


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## klw

Can you share any info on tools, set up, and how it's actually done? That would be very interesting…

Thanks.


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## fge

I'm all ears… First though, let me say very nice job.

We are only in our first couple of months with a CNC and have been flat cutting dovetail, but I cheated in that I rent out the Mozaik program. It works for us but I bet your deal is a ton cheaper.

Keep us filled in. Those are some really nice looking dovetails.


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## TheFridge

They look as close to perfect as you can get.


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## JayG46

Those do look absolutely beautiful.

It seems like the orientation of the piece would be an issue. For instance, cutting trough dovetails on a vertically oriented piece would be relatively straight forward (like you were using a Leigh jig), but if you had to do it on a horizontal piece, you would have rounded corners since you are using a spinning bit, correct? So if yo were working on drawer sides or a large case, could you still do through tails without a 5 axis machine?


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## Ger21

> Can you share any info on tools, set up, and how it s actually done? That would be very interesting…
> 
> Thanks.
> 
> - klw


They are cut vertically. You need a jig or fixture to hold boards vertically, and the spindle needs to be able to reach past the boards by at least the tool diameter. Length of boards will be limited by roughly your table height, depending on the machine design.
For half blind dovetails, one board is cut horizontally, and both boards can be cut in one operation.

Ideally, you'd want a fixture with both vertical and horizontal fences. But you don't need the horizontal fences for through dovetails.
If the fixture is permanent, or in a repeatable location, it's simple to set up a work offset, so no zeroing is necessary, except for the Z axis.
My current router actually doesn't have the ability to mount work vertically, so the samples were cut clamped to a block of wood bolted to my table.

In the samples, all the material is 5/8" thick.
The half blind joint uses a 1/2", 14° bit.
The through dovetail joints were done with a 5/8", 8° bit, and a 1/4" 2 flute upcut spiral bit for the pins. These happen to be the only dovetail bits I had. I need to order some other sizes and make some more test cuts.

I also use the 1/4" spiral to do roughing passes, removing the bulk of material before the dovetail bits are used. My homebuilt machine isn't the most rigid, so this gives a better quality cut for me. The roughing passes are optional.

The software ouputs both ShopBot code, and generic g-code that works with Mach3, LinuxCNC, and many others.

While I guess you could use a 5 axis to cut these, my program won't write 5 axis code. It wouldn't be very cost effective to use a 5 axis machine for cutting dovetails.

Here's a video showing how a test joint I did a few months ago.


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## SPalm

Hey Gerry,

Those look really nice. Your machine looks rigid enough.
Did you cut a slot in your table top? Or extend out the front?

Good job, 
Steve


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## helluvawreck

That is some great looking dovetails.

helluvawreck aka Charles
http://woodworkingexpo.wordpress.com


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## brtech

Many CNC machines that hobbyists use have 8020 (or equivalent) extrusions holding up the table. You can usually adjust the setup so that the tool can travel off the edge an inch or so with the carriage staying on the rails. It's easy to put some work holders to hold a board vertical for this process on the extrusion. The trick is getting the whole machine up high enough that all your work pieces fit. If all you are making are boxes or drawers, no problem, but cabinet parts might be a pain. Most the the machines I've seen have the bed pretty low to the ground.

I've seen some tables where the table top extends out a bit from the extrusion. You could fabricate a spacer to pad out the extrusion so you have a firm vertical surface to clamp to.

While my machine is currently out of service due to a complete shop re-org (and other projects seem to get in the way), I've adjusted mine to be able to do this. I'd like to try your code when I get it back on-line.


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## dannelson

I've seen your posts on other forums but never a link to purchase. Are you planning to do so soon? I have done these in Vetric software before with a vertical jig, are yours cut the same way? Do you need a beta tester ? Awaiting your reply thanks Dan Nelson [email protected]


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## Ger21

> I ve seen your posts on other forums but never a link to purchase. Are you planning to do so soon?


Hopefully in about a month.

Yes, they are cut vertically. Watch the video I linked to above.

I think you'll find this far easier than trying to do them in V Carve Pro. No drawing or CAD work needed. No need to figure out where the toolpaths should go.
Just enter the size of your board, and the size of the dovetails, and you get a preview of what they'll look like.

Not looking for any testers. It's pretty much ready to go right now. I'm just working on a manual, website, and tutorial videos right now.


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## Gshepherd

Excellent Job on the Dovetails…..


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## DiggerJ

That is a thing of beauty! And thanks for working with me on my cnc posts.

Is that the machine on your website?


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## Ger21

Yes, it is.


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## DKV

Beautiful and perfect. Can you post a video for us?
Thanks,


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## Ger21

See the 5th reply.


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## DKV

Thanks Ger21, great video but I had to go to one of your three year old videos to actually see the machine.


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## Ger21

See my projects for more info on the machine.


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## DiggerJ

I am putting together my CNC router table and planning to make a pop-out section in the table with clamps to make use of a program like yours. I am using the Open Builds OX build, upsized with large router/spindle and table size. Could you give me any more details of your app and/or ideas/pricing to take into consideration with this build?

Thank You


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## Ger21

Not sure what kind of info you're looking for. I'm not releasing any pricing info just yet.

The program can create g-code to cut two joints at a time, a left hand and right hand joint. Ideally, you want a vertical fence on each side of the fixture that holds the boards vertically.
For half blind dovetails, you also want a horizontal fence on each side.

If you search Youtube for CNC dovetails, there are several video by other users that show their methods for mounting boards for dovetail cutting. While the users in these videos used different methods to generate the g-code, the basic procedure is similar.

When cutting dovetails, precision is incredibly important. Fixtures must be square, and your fences must be accurately located in relation to your zero positions. 
Machine rigidity is also very important. I suspect that the OX is not all that rigid. So you may have to cut with multiple shallow passes, as I show in the video, for best results.

If you have any more specific questions, I'll be glad to answer them, but I don't really know what else you might want to know.


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## DiggerJ

That is pretty much the info needed. Just have to plan out the table top pop-outs and already have the v-slot reinforcements under control.

It is interesting that many people seem skeptical of the OX build until they see one and comment how sturdy it is. My build will be oversized and built on a sturdy table. Also additional supports from side rails to lower structure for additional support. First mockup of lower table will be wood, and once proper changes have been noted, we will build a steel support table. It is a home/hobby unit, so I can live with some slower feed rated if needed.

I look forward to your app and all of the great things it looks like it will do!


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## Patwantagh

Hi new guy here-those dovetails look great-I just picked up a omnitech cnc -Im doing basic kitchen cabinets with Cabinet vision-I would love to add those to my cabinets-If any one is near me on Long Island-I would be happy to show you around the shop.


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## Ger21

I should have it available for purchase in the next day or two.
http://g-forcecnc.com/jointcam.html


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## Ger21

I got a few new bits in to cut some different samples. If the boards are thicker than the bit length, a rabbet is automatically added.



















One of my users tried a double dovetail and this was the result of his first attempt.


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## DS

Looks real good. My home brew machine could accommodate something like this. Your post has me thinking about it for sure.


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## Ger21

I've now added box joint capabilities as well.


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## Ger21

I've added two more types of box joint.


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