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Discussion Starter · #1 ·
I have a machinist's level that goes in a box. The box is damaged and I'd like to make another one, or at least repair the existing one. I have 2 questions:

1. I've included a picture showing the size of the finger joints. What would I use to make these? I have a Leigh jig, but I don't think I can route fingers this small. Would I set up a dado blade and use a fixture of some sort to get the correct and even spacing? They seem to be exactly 4mm, which is odd because this is an old American level (Starrett #98). However, they could be 5/32 which also seems like an odd number to use.

2. I'm also going to use oak because I have some. I think the original box is mahogany, but I'm not sure. Anyone see any issues with this?

Thanks!
 

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The easiest is with a dado blade and size is pretty much immaterial. I saw a video of someone who did some crude testing with different size fingers and a press with a pressure gauge to see how much pressure it took to destroy the joint with different sizes of fingers and there was very little difference between any of them. So make them with what ever is convenient for you.

There are quite a few articles on making a jig and also quite a few videos on the same. Just google box joint jig and finger joint jig. Both terms are used for the same thing. If you think you might want to do lots of them then I recommend either the Incra I box jig or an LS positioner. Here`s a link to a magazine article showing how to make one. It may require some fine tuning after to get the spacing right. https://www.woodmagazine.com/woodworking-tips/techniques/joinery/box-joint-jig
 

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my 1st choice would be to use the table saw and a shop made sled to make those box joints.....
Here's some ideas to work w/....

.
 

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I just got this video in my emails from Fine Woodworking and it may be easier to follow. https://www.finewoodworking.com/201...tm_content=fw_eletter&cid=76047&mid=943761398
At the beginning he says you need a box joint saw blade but a dado blade is just as good. In the above mentioned strength test the person doing the test even tried one joint with eigth inch fingers which you could do with a full size flat top ripping blade but there was no strength advantage to doing that and it was more work.

The first critical part of doing this is to get the key exactly the same size as the thickness of the blade(s). That`s easy to do by cutting a groove and then work on the key until it perfectly fits the groove. The video shows how to make adjustments after doing a mock up with scrap.
 

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You have received some great advice on making a box joint jig. There are several slight variations, but all will produce good results if you can get them adjusted just right. I strongly suggest that you get yourself a dial or digital machinist's caliper, because you will need the wood pin, the blade, and the space between the pin and the blade to be accurate withing a few thousandths of an inch. You cannot do this with a tape measure. Without one, you will likely spend all day making scrap, trying to get everything adjusted just right. The jig that @Stick486 posted is a very good one. It even has the replaceable sacrificial strip. You will need a new one of these each time you change the blade height position or change the blade. It keeps the blade from chipping out the back side of your work piece as the blade teeth exit the wood. You can use a dado blade, but the bottom of the cuts are frequently not flat using them. They sell Box joint blade sets that cut 1/4 & 3/8" box joints that are perfect, but for 1/8" box joints, I use a Freud Ripping blade that has a flat square tooth FTG grind and it makes great 1/8" box joints. You may already have a ripping blade with these square cut teeth. ATG Alternate Tooth Grind combination blades do not work very well for making box joints. I have tried about every other way to make box joints and the best and cleanest cuts have been with the table saw, the right blade, and a good jig with a sacrificial insert.

I make a lot of boxes using box joints of different sizes. If you are like me, you will end up getting the 1/8" FTG Ripping Blade and a 1/4-3/8" box joint blade set plus an Incra I-Box jig like I did, because I make a lot of box joints of different sizes and the I-Box jig is so easy to adjust, but don't spend all this money now. You can get very good box joints for this small box using a good ripping blade and a shop made jig. Tight fitting joints are achieved by building the jig accurately.

Charley
 

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another plan to add to the mix...

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Discussion Starter · #9 ·
Thanks to all for your ideas and suggestions. The videos were also very helpful. The Incra Positioner sounds really cool, but it's out of my budget and I don't make enough of these to justify it anyway (not that that would stop me, but the Budget Committee President, aka Wife would not approve!).

It sounds like they do not make dovetail jigs this small (I didn't think so, but I thought I'd ask), so I will use one of the sleds mentioned above.
 

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So guys, why wouldn't you use a finger-joint router bit?
I understand the use of the table saw, but I'm confused as to why you wouldn't use a bit in the router? Fully adjustable, repeatable..... Yes, you'd need a backing block to reduce tearout (no different to the table saw it seems), but I'm struggling to understand they "why not"?
 

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Fair enough, terminology accepted (although seems to be interchangeable according to the interwebs usage of it).
Doesn't answer the question, and given the original box, still seems like a candidate to consider.
 

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Fair enough, terminology accepted (although seems to be interchangeable according to the interwebs usage of it).
Doesn't answer the question, and given the original box, still seems like a candidate to consider.
that happens often w/ many things...
 

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So guys, why wouldn't you use a finger-joint router bit?
size limits... (height)
and it'd be a box joint bit... it's tough to make 90° turns w/ a finger-joint bit....
the bit pictured is average size..

.
 

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FWIW...
box on the left, finger on the right....

 
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size limits... (height)
and it'd be a box joint bit... it's tough to make 90° turns w/ a finger-joint bit....
the bit pictured is average size..

What do you mean about the 90 degree turn? Surely you route the ends, and then just simply push the joint in at a 90 degree angle, anticipating you've only cut a depth into the stock the same as the width of the stock. I don't see the difficulty.

Seems logical to me, but I haven't tried it yet (got a bit, might try someday soon).
 

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assembled 90° box joints...

 

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assembled finger joint...
there is no 90°'ing this joint...
it's a board stretcher joint most commonly found in paint grade moulding where a length of moulding is made up of numerous short pieces...



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Okay, yes, I get the difference. What I'm asking is if the box joint router bit be used to create the joints required for the new box, why would you use the table saw over this method?

THAT's the question I want answered
 
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