Trouble with box/finger joints

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Forum topic by nfpotter posted 03-01-2017 04:03 AM 5251 views 0 times favorited 25 replies Add to Favorites Watch
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5 posts in 809 days

03-01-2017 04:03 AM

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?

25 replies so far

View pintodeluxe's profile


5913 posts in 3171 days

#1 posted 03-01-2017 04:21 AM

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.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View waho6o9's profile


8636 posts in 2934 days

#2 posted 03-01-2017 04:24 AM

Enter William Ng ^^


Welcome to Lumber Jocks nfpotter!

View johnstoneb's profile


3099 posts in 2530 days

#3 posted 03-01-2017 04:39 AM

x1 pinto

-- Bruce, Boise, ID

View Andre's profile


2568 posts in 2163 days

#4 posted 03-01-2017 06:46 AM

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?

-- Lifting one end of the plank.

View jerryminer's profile


951 posts in 1799 days

#5 posted 03-01-2017 07:15 AM

+ 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.

-- Jerry, making sawdust professionally since 1976

View Woodbum's profile


869 posts in 3423 days

#6 posted 03-01-2017 12:18 PM

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!

-- "Now I'm just another old guy wearing funny clothes"

View JRsgarage's profile


361 posts in 867 days

#7 posted 03-01-2017 01:51 PM

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


buy or make, setting up can be tedious

-- “Facts don't care about your feelings.” ..., Ben Shapiro

View nfpotter's profile


5 posts in 809 days

#8 posted 03-02-2017 01:20 AM

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.


View EricLew's profile


237 posts in 1723 days

#9 posted 03-02-2017 05:08 AM

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

-- I love the smell of coffee in the morning, and sawdust in the afternoon

View jumbojack's profile


1686 posts in 2981 days

#10 posted 03-02-2017 05:34 AM

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

-- Made in America, with American made tools....Shopsmith

View bandit571's profile


22742 posts in 3041 days

#11 posted 03-02-2017 07:35 AM

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

-- A Planer? I'M the planer, this is what I use

View Madmark2's profile


451 posts in 946 days

#12 posted 03-02-2017 07:52 AM

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.


View Redoak49's profile


3925 posts in 2346 days

#13 posted 03-02-2017 11:58 AM

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.

View jerryminer's profile


951 posts in 1799 days

#14 posted 03-02-2017 08:37 PM

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

-- Jerry, making sawdust professionally since 1976

View nfpotter's profile


5 posts in 809 days

#15 posted 03-03-2017 01:09 AM

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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