# Can't get finger joint jig right



## SouthFloridaSun (May 21, 2013)

After deciding I wanted to start learning a few wood joints to use rather then my Kreg pocket hole jig all the time I settled on the finger joint as a first. I looked over lots of jig plans and decided to make this one because it was in the middle of the road between plain and fancy



















I wont go into the details of the jig but I had scraps of 1/4" purple heart which as you can see I used for the key. The key is absolutely 1/4" from the blade and the blades are 2 stacked 1/8" dado blades equaling 1/4".










Here is my issue. If the blade cuts 1/4" and the distance from the blade to the key is 1/4" a 1/4" finger isnt going to fit in a 1/4" hole so what is the general rule of thumb? Should I make the distance from the blade to the key 1/32 less then 1/4"?

P.S. I am going to bolt the removable fence to the back fence after I am confident its all good.


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## JustJoe (Oct 26, 2012)

*If the blade cuts 1/4" and the distance from the blade to the key is 1/4" a 1/4" finger isnt going to fit in a 1/4" hole *

Huh? I'm not following the math. A 1/4" finger will fit in a 1/4" slot.

If your blade cuts a slot (X) wide, then you want your key to be (X) wide and to be (X) from the edge of the slot that the blade cuts.


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## SouthFloridaSun (May 21, 2013)

A 1/4" finger fits in a 1/4" hole sure but with a bit of force. My questions is what is "too tight"


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## JustJoe (Oct 26, 2012)

You want it to be a nice slip fit. You shouldn't have to force it. And to keep it accurate, you want the distance between the key and the blade to be as close to perfect as you can get. So if your blades are 1/4", make that slot between the blade and the key 1/4" and then take your block plane and just wave it in the air at the other side of the key until you've scared away 1/1,000,000th of an inch, so the key is maybe .2499999999999" and then when you're cutting the fingers your board should slide right over the key. And then take the same blockplane and relieve the two top edges a bit, that will make it easier to lift/drop the board over it.


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## unbob (Mar 10, 2013)

If this photo does not work, I will try another.
My jig looks much like yours, but I have bolts instead of clamps to hold it.
These are guitar amplifier boxes. the joints are long. To make this work, I add .004" shim for the mating part. This gives .002" per side of the slot. If it did not have this clearance it would not go together.
I have a bunch of other tips, if you are interested.


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## juniorjock (Feb 3, 2008)

I'd listen to unbob. He knows what he's talking about. If your boards move any when making the cut, the joint will be off.


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## bowedcurly (Aug 31, 2013)

hold the board tight and do it the same way every time and you will get good joints, the trick is in the setup make sure to mark your boards and cut one corner then the other, the way I do it is cut the front of the box then the back of the box, the real key is shimming your box joint set to get really great joints


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## bowedcurly (Aug 31, 2013)

I think this is another pic


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## bowedcurly (Aug 31, 2013)

I made these joints with the Forrest box joint set and use 2 shims to make them perfect fit that's perfect for me best joints I have dome to date but the Box joint set really makes it easy


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## bowedcurly (Aug 31, 2013)

the second pic is from the forrest box joint set, the first is with a Frued safety dado you can tell a big difference


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## bowedcurly (Aug 31, 2013)

I don't really measure I just pick a look and try to get a good slip fit not tight but not loose either shimming is the way I do it


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## unbob (Mar 10, 2013)

I did these a few years ago, this photo shows some progression in quality. I read about all I could find, some not so helpful. Many ways for error to creep in, get one slot off the following ones will be off, induce accumulative error on every slot, with long joints the end ones will be way off. The box on the right is how I want them to be, the wood looks stitched together.
I have it now where I can put 40 or more 1/4" slots together near perfection.


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## Skippy906 (Dec 16, 2012)

I found this plan on the net and made perfect box joints. I kinda amazed myself at the ease of this project.









This is Lynn's box joint jig. There are are few plans out there of this jig, but this is the one I chose.

Here is the box I made and the fingers matched up perfectly.









This is the only box i have made with this jig, but it is another tool in the toolbox for another project.


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## comboprof (Aug 26, 2013)

Get out your caliber's and measure the actual width of the dado that your 2 stacked 1/8" blades make.
Mine don't make 1/4" instead its 15/64". I adjusted my keys to also be 15/64", but I will admit my joints are very tight and I may try shaving the fixed key as JustJoe says. Alternatively my jig has micro adjustment so I may try that first. BTW I made two 15/64" keys one fixed in the jig and the other loose to help with the alignment of the "mate" to the first board. Also if you cut two sides at once you can use the loose key to lock them together once you have
a free finger hole.


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## MrRon (Jul 9, 2009)

I understand your problem. It is a common one. What I do is taper the sides of the pin slightly so the work you are cutting fits firmly over the pin, but easily due to the tapered sides.


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## DaddyZ (Jan 28, 2010)

Even modified box joints are cool


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## jaynolet (Oct 25, 2012)

When I made mine, I made a first 1/4" dado cut in the back board. I then cut a 1/4" key. I calipered it at .254". I then sanded the key until it fit into the dado cut. It slid in nice and smooth. I glued it in place. I spaced the key as close to .250" as I could. I cut my first dado in my project. The dado cut of the project fit in the key as nice as the key fit in the back board dado cut. Nice and smooth. Once I got the spacing right, I found out that when I put the last dado cut in the key to make the next dado cut I had to push to the right consistently to keep a consistent (to the .001", yea I said that) width of finger. Project came out spoony. spoony - Angry Beavers cartoon.

Jay Nolet


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## bowedcurly (Aug 31, 2013)

shimming shimming DRILL DRILL DRILL


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## unbob (Mar 10, 2013)

MrRons explanation of a tapered key indexing fit is the best solution I found to that problem.
Jay Nolet above solution does work, but at times a mistake can happen "board slips over", then it can be a major down the row alignment problem.








These sewing boxes my wife designed " still in progress" presented some problems, well, the cost of the camphor burl on the left added to drama on my end for sure. The one on the right is a maple burl. Both have birds eye maple framing.
The birds eye maple wants to blow out badly, so I used thin drawer bottom plywood for a backer, moving it along with the board as the joint progressed. Any blow out inside or outside looks bad.
I used 1/4" box joints on these because the sides are only 3/8" thick and have to be strong yet light weight.
This is one area where 1/64" is not good enough, that much of a gap would look really bad.
I am not saying my way is the best way, just working for me.
Here are some other pinch points I have encountered.
The solid woods are best planed, jointed, and put together quickly-within hours, not days. The joint may fit together now, but probably not in 24 hours.
The wood must be flat against the jig, if it is cupped or twisted even a little, the joint will wander off.
Regular water based wood glue will swell the pins, making assembly very hard on long joints, the joint may seize even using Tightbond 3.
I use slow dry epoxy on these, epoxy acts like a lube, doesn't swell the pins, easy to bottom out the pins.
One other thing I learned the hard way, when doing this on expensive woods, do some test pieces first, the jig may have swelled or shrunk, and need some tuning. Those test pieces can be used as a gage as the slots are cut.


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