# Trouble with box/finger joints



## nfpotter (Feb 28, 2017)

Howdy, y'all. New member, 1st post. Not entirely new to woodworking, but let's consider me a novice, just to be safe 

I am new to box joints, and mine are coming out too loose. I have the Freud 8" super dado set, and the Delta 36-725 table saw.

All of my joints are coming out with .006-.016" gaps, both randomly and depending on material, so I never get a fit anywhere close enough to hold itself together. I know about leaving room for glue, but I want to start tighter.

My saw has about .001" runout at arbor, nothing measurable on the shaft. My tests have all been at .5" setup, and the dado stack measures just under .5" as it should. I have built several "basic" box joint jigs out of good materials, and with indexing fingers that are crazy close to exactly .5".

I'm still getting sloppy, loose finger joints. Ideas?


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## pintodeluxe (Sep 12, 2010)

If there is inconsistency in the fit of the fingers, I'm guessing the indexing pin on you jig is too narrow.

I've made a few good tablesaw jigs for box joints. They all work well, but it's tough to avoid tearout.
I ordered a special bit for asymmetrical box joints on my Akeda jig, so it'll be interesting to try that. If it cuts finger joints as well as it dovetails, I will be happy indeed.


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## waho6o9 (May 6, 2011)

Enter William Ng ^^

HTH

Welcome to Lumber Jocks nfpotter!


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## johnstoneb (Jun 14, 2012)

x1 pinto


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## rad457 (Jun 15, 2013)

*If there is inconsistency in the fit of the fingers, I'm guessing the indexing pin on you jig is too narrow.
*
and or pin to far from blade?


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## jerryminer (Jun 15, 2014)

+ 1 on above. Technique matters, too.

Each pass over the blade has to be just like the previous pass. I make a point of pressing the jig toward one side of the miter slot and always with the same pressure toward the same side. You may also find that removing the stock before pulling the jig back for the next cut might help.


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## Woodbum (Jan 3, 2010)

First of all, WELCOME TO LJ!! Wm. NG is a good source. I have built shop made box joint jigs in the past that worked well; as well as cut box joints on an old Incra Twin Linear router table fence set up; as well as a Leigh D4 jig. Then I bought an Incra I-Box jig and use it with my Freud Box Joint blade set on my Griz 1023 for 1/4 and 3/8 finger joints. For bigger joints, I still use the D4 with a PC 690. Save up your pizza and beer money for an I-Box. It is east to use and well worth the money. I was fortunate to have had a good income that allowed me to buy my numerous, good, woodworking tools over many years prior to my forced retirement; since money is not so plentiful now. Good Luck, Work Safely and Have Fun!


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## JRsgarage (Jan 2, 2017)

> *If there is inconsistency in the fit of the fingers, I'm guessing the indexing pin on you jig is too narrow.
> *
> and or pin to far from blade?
> 
> - Andre


+1

buy or make, setting up can be tedious


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## nfpotter (Feb 28, 2017)

Thanks much for the input, y'all!

My latest index pin is .5025", so I'd think that would be good for .5" cuts. I have been using a 1/2 inch brass setup block (measures .4985 to .5) to get initial positioning. I've kept everything tight and only run my workpieces through forward, not backward.

My cuts are about .5145 to .5190 through most materials, including hardwood. I'm getting .007-.008" runout on either side of the dado stack when at full height, test just below the gullets. That seems about normal, yes? The size of the cut seems way too big.

Ideas?


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## EricLew (Aug 29, 2014)

I started making keepsake boxes recently with 1/8 inch finger joints. I made a jig but had the same issues, too tight or too loose. It was very frustrating, especially wasting so much expensive exotic wood that I was using. I made test cuts using cheap pine, but the joints never came out the same twice. Then I bought an Incra Ibox, what a great tool. The first go didn't come out perfect, but a tweak of the micro adjuster got them dialed in perfectly, with repeat ability.

It's not a cheap jig, but it will save me a lot of money by not wasting stock, and I have a garage workshop, the Ibox can be adjusted for any size box joint, so I don't need to make a separate jig for every different size


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## jumbojack (Mar 20, 2011)

For flawless finger joints see Ed Stile on youtube.
I reverse engineered his jig and it is everything he claims it to be.


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## bandit571 (Jan 20, 2011)

Guess all of this is why I hand cut all of mine…..


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## MadMark (Jun 3, 2014)

Use a router instead of TS. The router bit will give you perfect 0.500" wide flat bottom fingers every time. Also consider a leadscrew indexer instead of a block jig - block jigs tend to accumulate errors.

M


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## Redoak49 (Dec 15, 2012)

I have found that to get the perfect fit each type of wood may need a slightly different setup both with finger joints and dovetails. You have to make very small adjustments to get it right.

I agree that a router seems to work best but either will work just fine.


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## jerryminer (Jun 15, 2014)

> My latest index pin is .5025", ...My cuts are about .5145 to .5190 The size of the cut seems way too big.
> 
> - nfpotter


The index pin needs to match the cut. I make a sample slot first, then make a pin that matches the slot, and set the spacing accordingly


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## nfpotter (Feb 28, 2017)

But doesn't it seem odd the cut is that much wider that the stack, give the small amount of runout? Can anyone say whether they get similar results?

I'm not interested in the router option right now, but thanks for the suggestion.


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## Hammerthumb (Dec 28, 2012)

The index pin needs to match the cut. I make a sample slot first, then make a pin that matches the slot, and set the spacing accordingly

- jerryminer
[/QUOTE]

This is where you are losing it. Make your index pin and the size of the spacing exactly the size of the dado cut. Or, adjust your dado blade to the exact width of the index pin. Don't get stuck on the exact measurement of your brass setup bar. If your dado width is .5145, make the index pin the same width.


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## nfpotter (Feb 28, 2017)

I guess I'm asking if it is normal for a $200, highly rated dado stack to cut that much over. Why am I getting .5145 or more from a stack that measures .4950 or so, tooth to tooth? The cuts look quite nice and clean on the sides, and it's similar in different types of wood.


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## jerryminer (Jun 15, 2014)

Several possibilities for why the cut could be wide:

run-out in the arbor

dado set not perfectly parallel to miter slot (or whatever the jig reference is)

piece of sawdust or grit between the plates of the dado stack-or between stack and arbor washer

dado plate not flat

mis-ground tooth or teeth

Most likely one (or both) of the first two


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## HorizontalMike (Jun 3, 2010)

I would like to mention that that "0.0145" overage on EACH dado cut is ADDITIVE.

In other words, after cutting lets say ten(10) finger joints in one board length, you will be OFF by 10×0.0145in (overage), or a total of 0.145in on that tenth finger of the finger joint. Mistakes add up, hence the need to exactly matching the cut and the pin distance.


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## bandit571 (Jan 20, 2011)

Use the Olde School way….


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## CharleyL (Mar 10, 2009)

A good machinists dial or digital caliper helps a lot when doing this. You need the pin, space, and cut dimensions to be the same width, and not almost the same. Whatever width that your blade is cutting, is the width needed for the pin and the space. It has to be the same, not almost the same. The exact width of these isn't important, as long as they are all within a few thousandths of being the same width of each other. I've made a bunch of these jigs in the past 60 years, but I made firewood out of them two years ago when I bought the I-Box jig.

Charley


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## Lazyman (Aug 8, 2014)

+1 on the William Ng video. You will want to use a sled for precision. If you don't already have a sled, see his video for making one (or 2 so you have 1 for dados and 1 for cross cuts). He explains how to make it so it cuts very accurately. The crosscut sled is the most important accessory for table saw accuracy and safety in my opinion.


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## nfpotter (Feb 28, 2017)

Thanks much for the great tips/advice, everyone! Looks like I've got some expirementing to do.

I'll post results soon, cheers!


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## bandit571 (Jan 20, 2011)

"Finger gauge" 









"Table saw" Split the lines for the first set, saw inside the waste side of the lines to match the second set..









Finger gauge to remove half of the waste, flip over..









To remove the rest. Use these to lay out the matching fingers. Repeat…then test fit…









Wood was 1/2" thick Cherry, fingers are 1/4" wide. All done while sitting on a stool at my bench. 
Sorry, don't have the equipment to do a video…...


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## AlaskaGuy (Jan 29, 2012)

> Enter William Ng ^^
> 
> HTH
> 
> ...


I followed this video and got perfect joints the first time.


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