# Help with finger joints!



## LiveEdge (Dec 18, 2013)

I am making a few boxes for fun and decided to use finger joints on the corners. I made a little jig like you can see a million times on youtube, but things aren't going too smoothly. I chose to use 1/4 inch fingers over about 4 inches. That makes for eight fingers and I realized the problem with the jig is that any error in your spacing is compounded over each joint. If you are off by only 1/100th of an inch you are still out about 1/12th of an inch by the end.

A few solutions came to mind. One, I could use fatter fingers. Fewer joints mean fewer compounding errors. Two. If I could cut all four pieces without moving the fence, then the errors would match on each piece and they would still fit. The problem is I can't figure out how to do that while still offsetting two of the pieces so each finger meets the proper gap of the joining piece?

Tips? This shouldn't be this hard…


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## bondogaposis (Dec 18, 2011)

Show us a picture of your jig.


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## LiveEdge (Dec 18, 2013)

It looks like this:

http://www.startwoodworking.com/sites/startwoodworking.com/files/uploads/1/7052/box-joint-lead.jpg


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## PLK (Feb 11, 2014)

Fewer joints don't mean fewer errors. If your spacers and blade aren't identical every joint will be out of place.

Measure your blade width and both the spacer on your jig and the spacer for your second joint piece with a digital caliper. They need to be within 100th of each other. I had a very hard time with cutting box/finger joints on my saw before I picked up a digital caliper and could properly measure.

Paul


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## LiveEdge (Dec 18, 2013)

I think I just visualized how to start the second piece without moving the fence. That will help, I'm sure. I'll look into some digital calipers, but I'll probably goof around some more tomorrow.


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## PLK (Feb 11, 2014)

To start the second mated piece you just put an equally wide spacer next to the spacer installed on the fence. You should not be moving the fence at all.

Paul


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## PLK (Feb 11, 2014)

Other than on your miter slot I should have said. once you make the fence it's set and should only be used for back and forth cutting of the joints.

Paul


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## distrbd (Sep 14, 2011)

If you butt the two pieces((that are supposed to join together to make an *L* shape) against each other when cutting them,there's less chance of error in your spacing .this youtube video explains what I'm talking about:


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## PLK (Feb 11, 2014)

Steve's video's are normally great. For someone trying to get it right and tight for the first time it's a good watch to learn the basics but as he even states it's not perfect.

The OP is trying to get tighter joints.

Paul


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## LiveEdge (Dec 18, 2013)

Well, I'm just trying to get them to fit. . I had seen that video before and it's the one I based my jig on. I'm going to give it a go again. I think my biggest problem was I was moving the jig to cut the second two pieces and that introduced a whole second set of errors.


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## distrbd (Sep 14, 2011)

I understand and agree 100% Paul,you wouldn't believe how many boxes I scrapped until I finally got it right by making sure (as you mentioned) the gap between the blade and the spacer is exactly the same(as the thickness of the spacer),having a dial caliper was essential.


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## PLK (Feb 11, 2014)

LiveEdge,

Like Ken just stated I scrapped a TON of joints before I figured it out. Don't get discouraged it just takes alot of practice.

Paul

PS get a caliper  a $20 once from HD will be enough to put your mind at ease, at least for box joint and finger joint projects.


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## neverenougftackle (May 6, 2013)

You will notice at the point of 2:11 in his video where he states that the distance between the pin and the blade,,,,,,wrong ! On this type of TS blade there is a series of teeth that is offset. these teeth protrude slightly to the outside of that blade. He at this point is pointing to the other set of teeth that is NOT off set but centered.

Now this does not seem to be that much of a difference, but as you already noticed it does not take that much for the finger joints to not mesh, and the longer the board to be joined the more the differance.. So that the outside of that first cut threw his 18" back up board,,,both of the outside cut of that openings/ the kurf cuts R&L side into that board is controlled by the off set teeth. Thus if he/you measure from the straight tooth you will be off by the width of that off set of the off set tooth.
You do not measure from the blade as he said, you measure from the off set teeth that is the closes to that pin, that equals where the distance is going to be double the size of that pin and where that side of the cut of that opening is going to be…...it is the teeth that makes that cut not that blades side.

By the way,,,making a guess in your all of your shop time how many more times would you conceive that you will be making any more Box Joints. I ask my self that same question on failing at this pin set up that you are doing some time back. I went on to make Shopnotes Magazine's adjustable Box Joint Jig and never have regreated it. It will solve all of this ,"Blank", back and forth guessing once an for all,,,look it up.


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## PLK (Feb 11, 2014)

That was the long legged lady like way of saying get a caliper and measure correctly. I thought we already covered that but maybe not.

Paul


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## unbob (Mar 10, 2013)

A couple of things that helped me.
The fixture pin needs to be a tight fit in the created slots. Otherwise, with a loose fit fixture pin, there can be a slight shift that adds up accumulative error. The pieces may not fit, it does not take much error.
The fixture face with pin can be attached to a back board so as it can be shifted slightly, makes things go better.

Some wood I do such as spruce, is fragile. Not good to use a mallet to knock the sides together with that wood, it chips out easily.
I use a .004" shim in the blade stack to cut the mating pieces. Since I do that, I shape the fixture pin a little like a wedge, so as both sized slots will fit the fixture pin without side movement.

Long pieces and many slots, get a little more demanding. Errors from a board cupping and not sitting flat against the fixture can make a mess of things where as the pieces may not go together.

Cutting the slots, and the parts fit now, may not fit tomorrow from stress changes in the wood "twisting and cupping. I found it best to prepare the boards, cut the slots, and get it together as quickly as possible within hours not days. 
On some woods, or on very long joints, water based glue can swell the pins enough the joint will not go together or will seize part way together. There I use slow dry epoxy, doesn't swell the pins, and acts like a lube.

Do a lot of test pieces, you will get the hang of it.


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## Redoak49 (Dec 15, 2012)

Unbob had some good advice. I have worked at building several jigs and this is the one that works the best for me. Note that there is a machine screw on one side that is used to adjust the distance between the blade(or router bit) and the notch. I have found that with the same exact setup, there are differences between making a box joint in pine versus oak versus poplar. Being able to do very fine adjustments makes a huge difference. Good Luck


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## LiveEdge (Dec 18, 2013)

Well, second go was MUCH better. Calipers and not moving the jig seemed to do the trick. The pin might have been a little tight because I had to force the piece onto the jig and that made me worry about wobble, etc.

Can you ever make finger joints too tight? And do people sometimes not bother to glue them? It seems like a high friction joint and I can't imagine getting glue in there anyway. Here's a rough assembly, no sanding.


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## Mahdeew (Jul 24, 2013)

Ouch!, that is a beautiful maple; but it can be repaired with a little maple dust; or end-grain slivers.


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## LiveEdge (Dec 18, 2013)

. I get a little excited to try things on "real" wood. Don't worry, it was only about $4/bf and there's more where it comes from. I can just keep making the box smaller. . I think the tightness of my pin was working against me as it made it difficult to have the piece perfectly sit against the jig (allowing for tearout) and it may not have sat perfectly flush against the table saw top which made for small variances in the depth of the cuts. Going to work some more on it with a slightly looser pin.


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## unbob (Mar 10, 2013)

I ended up with a jig just like Redoak49 above, and it works pretty good.
To totally control tear-out, I have to use a backup piece, usually thin plywood, and move that along with the piece being cut. Otherwise, the notch in the fixture erodes, and different thickness of work leaves the top of the notch unsupported.
Some don't use glue, I do, I often make musical instrument speaker cabinets, they get knocked around in use and need to be strong as possible.
I am working on a fixture to index the notches, where the board or "boards" is clamped in one time, and is moved along by other means then the index pin. I will make that out of metal.
I need to speed things up, with the typical fixture it can take me 2hrs to cut 1/4" notches on 12" length, on 4 pieces.
Looking good there so far Live Edge, you are off to a good start!


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## LiveEdge (Dec 18, 2013)

Well, today showed further improvement. I slightly thinned the peg and took more time. I had a pretty good set and then a not so good set. It seems my struggle isn't as much the top and bottom interface of the fingers, but the fingers seating all the way into the space horizontally. I used as much clamping force as I could, but they just would go in any further.


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## bowedcurly (Aug 31, 2013)

you have to make sure when your cutting your joints that you have the wood firmly against your sled bottom, I have made that mistake lots of times that will really throw off your joints, I guess you know this already, but that's a big deal when cutting finger joints on a homemade jigster, and your spacer needs to be exact but no tight. from the looks of your joint your not holding your wood down firmly or your spacer is too tall make sure your spacer is no more than 2/3 the height of your boxjoint this will cause big problems if your making it the same height as your cut, experiment and shim after you have the recipe mark your shims so next time it will be a snap


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## gfadvm (Jan 13, 2011)

PLEASE stop using that gorgeous birdseye to practice with! You are killing me!

How bout I send you a truckload of 'practice pine' in exchange for that maple?

Seriously, get your jig set up to cut perfect box joints in pine, plywood, or whatever. Then break out the good stuff. I always cut a few in pine before cutting my project wood. I save a piece with perfectly fitting joints to use as my set up guide every time I use my jig.


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## LiveEdge (Dec 18, 2013)

I know. It's killing you. Luckily it was the exact same piece as I used before. I just cut the fingers off and tried again after more practicing. I AM practicing Inbetween, you know. . It is pretty though, isn't it. I got it in the regular maple bin so it was regular maple price which is why I'm not sweating it too much.


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## distrbd (Sep 14, 2011)

Yes it's purty,you should now be happy with the result,the problem with this process is if you stop using your jig for a while you'll be back to square one,in my case at least that was the case.


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## bondogaposis (Dec 18, 2011)

Here is an article w/ few tips that might help.


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## 49er (Jan 3, 2014)

I used key stock for my pin. The pin sits in a dado in the block and the block is adjustable left and right. The jig works well. I made three 1/4,3/8, and 1/2. With three jigs I don't have to adjust anything.


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