need help with a box joint

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Forum topic by skidiot posted 03-12-2009 06:17 AM 1672 views 1 time favorited 12 replies Add to Favorites Watch
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85 posts in 4211 days

03-12-2009 06:17 AM

Topic tags/keywords: joining

I have been trying to make a square box joint. I have no problem getting the pins and slots to fit nicely. I cant get the boards to line up when I put them together. It seems like the width of the boards have to be an exact multiple of the size of the pins and slots. Is this how it works or can any width board be used?

-- skidiot northern illinois

12 replies so far

View Gary Fixler's profile

Gary Fixler

1001 posts in 3948 days

#1 posted 03-12-2009 06:48 AM

It looks best if the fingers add up to a multiple of the width, so you don’t end up with a final, partial finger, but it isn’t necessary. What are you using to make the cuts? Router table? Table saw? hand saw and chisels? Are you using a fence? It’ll help everyone to know what you’re using to give you the right advice.

-- Gary, Los Angeles, video game animator

View marcb's profile


768 posts in 4239 days

#2 posted 03-12-2009 07:05 AM

Shopnotes had a design for a tablesaw box joint jig that the fence part was removable and had a screw as a stop to help fine tune setup.

I need to remake that jig because box joints where a breeze once it was tuned in.

You also need to use the last board to offset the next board. If you follow the correct order everything lines up, if you mess the order up nothing lines up right.

View johnnie52's profile


27 posts in 3933 days

#3 posted 03-12-2009 08:29 AM

It does help to make the slots in multiples of the width of the sides. I find that 1/4” works best on boxes under 6” tall and 3/4” works on most everything else that is taller. As you have already been told, make sure to use the first finished piece as the guide for the first cut on the next piece. Then when you make the other set, put the first piece cut on the first pass through first and follow it with the piece you cut second the first time….. Other wise it can get totally out of wack.

-- John - Tampa, FL - American components, Russian components..... ALL MADE IN TIAWAN!

View bhack's profile


349 posts in 4286 days

#4 posted 03-12-2009 02:52 PM

Marcb probably stated your problem. You must reference the adjacent boards. Mark each of the sides to show which is top edge and which is the inside or outside to keep all parts referenced correctly.

-- Bill - If I knew GRANDKIDS were so much fun I would have had them first.

View skidiot's profile


85 posts in 4211 days

#5 posted 03-12-2009 07:38 PM

Ok I am using a router table with a 3/8 bit. I have used the end of one board as the guide for the next but it still doesnt come out right no matter how I fit the boards together. Im obviously not doing something right. I hook the last notch of the 1st board on the fence guide then put the second board up against the first board then make the cut in the 2nd board. Also if the board isnt a multiple of the slot size can you offset the 1st cut so the partial fingers are the same size top and bottom?

-- skidiot northern illinois

View PurpLev's profile


8553 posts in 4214 days

#6 posted 03-12-2009 08:59 PM

what jig/setup are you using to make the box-joints? sounds like the referrencing line is out of alignment if there is even one in existance. any description of your setup and how you go about making those joints will help – pictures of the setup – even better as they will helpe everyone understand what you’re doing, and how it can be fine tuned for better results.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View skidiot's profile


85 posts in 4211 days

#7 posted 03-13-2009 01:33 AM

My setup is quite simple. Just a board clamped to the crosscut fence with a tab the same width as the slot sticking out 90 degress from the fence . The tab is exactly 1 slot width from the edge of the router bit.

-- skidiot northern illinois

View juniorjock's profile


1930 posts in 4331 days

#8 posted 03-13-2009 02:09 AM

It would really help to see some photos. I always cut the boards a bit winder than what I need. That way, after you make the box joints, you can trim the boards so you have an even number of pins and slots.

View skidiot's profile


85 posts in 4211 days

#9 posted 03-13-2009 03:54 AM

Ok I figured it out. Just me not undestanding the total concept as usual. And trying to do something not the way it is supposed to be done, as usual. Sorry for wasting everybodys time.

-- skidiot northern illinois

View juniorjock's profile


1930 posts in 4331 days

#10 posted 03-13-2009 12:54 PM

skidiot, if some of the posts got you pointed in the right direction, it wasn’t a waste of time on anyone’s part. That’s what the site is all about. Glad you got it figured out.

View Eduardo Rodriguez's profile

Eduardo Rodriguez

37 posts in 3937 days

#11 posted 03-24-2009 02:06 AM

If you gave me your e-mail I will send you a FWW article thats explain how to do it, no matter the size of the boards.

-- Tempus fugit...better work wood!!!

View Brad_Nailor's profile


2545 posts in 4523 days

#12 posted 03-24-2009 02:20 AM

Sounds like you were probably doing the same thing almost everybody does when making box joints for the first time. You need to use the adjacent piece to space the pins properly, as someone else metioned…I did the same thing the first time. I remember thinking that it was such an easy joint to make ..and it is but you have to take the time and plan things out and mark your pieces correctly so you don’t have to think too much about anything but cutting the joints when you start machining.

Like the JJ said..if a post got you pointed in the right direction then it wasn’t a waste of time…we actually like picking apart problems around here…keeps us from having to talk to our wives…


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