Box Joint Tips and Tricks?

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Forum topic by oakview posted 01-06-2012 10:44 AM 6932 views 0 times favorited 14 replies Add to Favorites Watch
View oakview's profile


55 posts in 2382 days

01-06-2012 10:44 AM

Topic tags/keywords: box joint jig tips

Wondering if you all could share any tips or tricks for getting box joints to line up a little better, maybe even perfectly. I make them using a table saw, stacked dado, and a basic box joint jig clamped to a sled rather than a miter gauge. The sled is square to the blade and there is no play in the sled runners. (See photo) I also use a micrometer to set the dado stack to the correct width for the pin size, usually either 1/4” or 3/8”

Invariably, no matter how careful I am, I end up with one or two sides that are higher or lower than the adjacent ones leaving me a hated sanding job to get both top and bottom flat. I also clamp the boards to the jig when running them across the dado.

I’d be very interested in how you set your jig up and what steps you do during the cutting process to insure even joints. And tips to make flattening afterwards easier would be welcome if you have any. I don’t have any sanding tools big enough, especially for the larger boxes.

-- ~^ DaveG ~^

14 replies so far

View JohnMeeley's profile


255 posts in 2358 days

#1 posted 01-06-2012 01:26 PM

My thoughts… If your not letting sawdust build up on the sled, affecting your cut, is your stock actually planed to consistent thickness? Allowing a build up in the miter slots? thus ‘lifting’ your jig? Don’t just go by your fit, actually measure your depth of cut on a bad result

-- "The greatest pleasure in life is doing what others say you cannot do."-Walter Bagehot

View SteveKorz's profile


2134 posts in 3739 days

#2 posted 01-06-2012 02:05 PM

I use the route-r-joint system from It is awesome! They come out perfect every time, it is ridiciulously easy. I can make box joints for all four sides in about two minutes. I have never made them on the tablesaw.

-- As iron sharpens iron, so one man sharpens another. (Proverbs 27:17) †

View oakview's profile


55 posts in 2382 days

#3 posted 01-06-2012 08:03 PM

John, I should have been more clear. It’s not the finger depth that’s the issue. The slight offset I’m experiencing is at the top and bottom of the boxes after assembly, where the box lid and base get installed.

The finger depth is consistent, it’s the offset that seems to be inconsistent. There must be a way with the simple jig I use to get pinpoint accuracy, then again maybe not. Dunno, just askin’ for ideas, tips and tricks. It might be the little things an experienced boxmaker does without even thinking about it.

-- ~^ DaveG ~^

View casual1carpenter's profile


354 posts in 2500 days

#4 posted 01-06-2012 11:54 PM

oakview, I see you have zero play in sled runners, true parallel sled movement to a verified 90 degree blade angle, and micrometer set dado stack. Your joints are near to perfect, just not aligned to box top and bottom.

I would assume that you index your cut by sliding the box part to touch the spacing guide. If the spacing guide was off I don’t think you would have good joints.

So the question is, how do you index the fingers in the corresponding part? I would consider making another guide spacer that could be placed to fill the gap between the permanent spacer and dado cut line, until you get your part secured. I’d think about making it easy to remove before starting your finger joint cuts.Then your second part would start the finger directly on the corner as opposed to one measure in. If all the parts are the same dimensions I think this method should help.

View Gregn's profile


1642 posts in 3008 days

#5 posted 01-06-2012 11:56 PM

Looking at your jig, it appears to have no micro adjust mechanism to adjust for that. It sounds like when you clamp the jig to the sled your not lined up and off a tad causing you to be offset. Just my guess.

-- I don't make mistakes, I have great learning lessons, Greg

View Greylion's profile


28 posts in 2697 days

#6 posted 01-07-2012 01:36 AM

I use a jig much like yours only I have some adjustment side to side on it (yours looks a lot better than mine though). I use a square rod of known dimension to set the width between pins (?) i.e. 1/4 – .250 and so on. I make sure that the rod rests against the outside of the saw kerf (the tip of the saw teeth bent toward the guide) and the guide and don’t snug it at all. So far I get pretty good results, top and bottom turn out even.
Hope this helps

-- Bill, "GreyLion" ,Montana, Eph 2:8

View oakview's profile


55 posts in 2382 days

#7 posted 01-07-2012 02:40 AM

I think Gregn might have hit the nail on the head. I use a second pin (loose and from the same piece as the fixed pin) to line up the second board cut. I stands to reason that if it’s not set exactly, the offset I’m describing will occur. And you’re also right that I don’t have any micro-adjust to compensate, other than moving the jig manually and that’s dicey at best.

I found a tip in a PDF manual on the Freud website that may solve the problem, though I haven’t tried it yet. The gist of it is, cut the first notch, reverse it and use the pin on that board to line up the cut for the second board. Cut the second notch, then stack the two boards, use the fixed pin to line them both up and cut the rest of the notches. See the diagrams I excerpted from the PDF.

This makes perfect sense. Any other thoughts?

-- ~^ DaveG ~^

View gfadvm's profile


14940 posts in 2715 days

#8 posted 01-07-2012 05:11 AM

Dave, I cut mine with the method shown in your diagram but I don’t stack or double boards. It is too easy to get one out of alignment but if you are willing to align the edges and then reclamp for each cut this will work. I find it just as quick to cut each board individually and I din’t clamp them to my jig.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View oakview's profile


55 posts in 2382 days

#9 posted 01-07-2012 07:22 AM

”I find it just as quick to cut each board individually…”

I did that using some scrap and found that worked better for me too. I found that in my case, if the board isn’t clamped below the midpoint of the piece, it will tend to move slightly. As you all undoubtedly know, small movement when cutting box joints multiplies the error significantly.

I don’t know if it’s the size of the dado stack I’m using (Freud SD508 – 8”) exerting more force. Also, the sled is made of surfaced beechwood and is pretty smooth, likely contributing to any movement. Anyone use anything on their jig, like a sandpaper backing, to stop or minimize movement between the board to be cut and the jig?

-- ~^ DaveG ~^

View ajosephg's profile


1880 posts in 3586 days

#10 posted 01-07-2012 11:18 AM

Sandpaper is essential to keep the work piece from creeping around. I use a Porter Cable router jig to make box joints. and guess what? It has sand paper on all the work piece surfaces. My Osborne EB-3 miter gauge also comes with sand paper to secure the work piece. As a result I use 80 grit sand paper (secured with double sided carpet tape) on all my shop made jigs as well.

-- Joe

View TimmyP's profile


36 posts in 2473 days

#11 posted 01-07-2012 02:17 PM

Dang, Joe, 80 grit paper? Seems that the size of the sanding granules would be so large, as to cause displacement of parts on their own. But if it works, it works.

View ajosephg's profile


1880 posts in 3586 days

#12 posted 01-07-2012 04:17 PM

Timmy – yeah sounds big, but since all the “grits” are the same size and equally distributed it doesn’t mess with dimensions. I suppose finer paper could be used, but I thought that since Osborne liked the coarse stuff, I wouldn’t re-invent the wheel.

-- Joe

View richgreer's profile


4541 posts in 3099 days

#13 posted 01-07-2012 04:27 PM

As another option – I have been very happy with this jig for the router table -

I don’t recall ever having a problem with the edges lining up.

However, I have stopped using it because I purchased an Incra system that works equally well.

I would gladly sell it for $30 plus shipping. If interested, send me a PM.

-- Rich, Cedar Rapids, IA - I'm a woodworker. I don't create beauty, I reveal it.

View oakview's profile


55 posts in 2382 days

#14 posted 01-07-2012 08:21 PM

That does it! Out to the garage to put sandpaper on the jig. Thanks everyone, all the friendly useful knowledge is what makes this forum fun to visit. Makes it easier to grow out of the newbie stage into someone who might actually know what he’s doing, even if just a little. :)

-- ~^ DaveG ~^

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