BoxJoint question.

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Forum topic by Psydoc posted 04-14-2019 06:55 PM 591 views 0 times favorited 6 replies Add to Favorites Watch
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3 posts in 361 days

04-14-2019 06:55 PM

Topic tags/keywords: boxjoint korschgen

I have been unsuccessful at creating reasonably good box joints consistently. I am trying to use a technique I saw being used called the Korschgen box(?) His jig uses wood pieces cut in the width of his dado blade. These pieces are lined up blocking a carriage. He lifts a wood piece and then moved his carriage – cuts and then moves another piece and so on. I’m using a 1/4 ” dado blade so I imagine I would need each board to be 1/2 ” – correct? Also, in a setup like that, how would you adjust for the size of the gap next to the finger?

6 replies so far

View dbw's profile


380 posts in 2320 days

#1 posted 04-14-2019 08:38 PM

check this out:

-- measure 3 times, cut once

View waho6o9's profile


8836 posts in 3260 days

#2 posted 04-14-2019 08:53 PM

View JohnDon's profile


99 posts in 1853 days

#3 posted 04-14-2019 10:05 PM

Okay, I’ll try to answer your question the best I can, rather than giving you an alternative jig design. From the video that Korschgen has posted, it appears that each of the “flippers” has to be exactly twice the width of your dado setup. Also, each flipper has to butt up tightly against its neighbor. You didn’t say how your joints aren’t fitting. If some fingers are tight, and some loose suggests that the flippers aren’t all the same width, or warped, or debris is getting trapped between them. If the fit is consistently too loose, the flippers are less than twice your dado width. If the fit is too tight, they’re wider than twice your dado. I don’t know how the jig adjusts for the matching fingers. My guess is that when you clamp that piece in the jig, you offset the alignment with a spacer exactly the width of your dado.The design of the jig is interesting- once you have it tuned up, it should go faster than the “mainstream” setup previous posters refer to. The width of your joint is limited by the number of flippers, while the typical jig has no theoretical limit to th number of fingers. Good luck!

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3 posts in 361 days

#4 posted 04-15-2019 09:41 PM

Thanks for the reply! I was thinking that the flippers could have a small spacer after each flipper that could make the fingers tighter or loose. I’m also wondering if it would be much simpler to just make a notch every 1/2 inch (for a 1/4” dado) and move the carriage over to the successive notches.

BTW, I have recently taken up woodworking and prior to starting this hobby, my only tool was a hammer which I rarely had use for.

Again, the replies were appreciated.

View Redoak49's profile


4529 posts in 2672 days

#5 posted 04-15-2019 11:53 PM

I will give you a couple of thoughts…

1. I have never been very successful making them on the table saw.

2. I made a jig to use on my router table which uses a key and I can easily adjust the distance between cuts by small amounts.. I have made 1/4”, 5/16” and 3/8” finger joints with this method.

3. With the router table method, I found that different species of wood need slightly different settings to get best fit.

4. I now make finger joints using a Leigh D4R jig.

View Woodbum's profile


913 posts in 3749 days

#6 posted 04-16-2019 10:22 AM


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

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