Knapp Joint

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Forum topic by hank1 posted 05-20-2012 11:24 PM 3516 views 0 times favorited 6 replies Add to Favorites Watch
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5 posts in 2165 days

05-20-2012 11:24 PM

I read with interest the forum about the pin and scallop (Knapp) joint and was wondering if anyone knew anything about the machine that made it. I had to duplicate some of these by hand a few years ago and ever since have been interested in how such a machine would operate.

6 replies so far

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10260 posts in 3612 days

#1 posted 05-20-2012 11:50 PM

About the machine:

Templates are available to cut the joint with a Wirth Machine or

From examining the drawings of the machine it seems to me
it operates more or less like a dovetailer.

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155 posts in 3251 days

#2 posted 05-21-2012 03:07 PM

You may be interested in templates for Woodworker’s Supplies Matchmaker

-- “The test of our progress is not whether we add more to the abundance of those who have much; it is whether we provide enough for those who have too little.” ― Franklin D. Roosevelt

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Dan Krager

3955 posts in 2199 days

#3 posted 10-13-2012 02:58 PM

OK. I’m officially hooked. I’ve studied these joints off and on since I first encountered them in furniture repair many years ago. I can visualize cutting the pins and moon sockets on the end of the drawer front with some sort of plug or round tenon cutter. Cutting the mating surfaces on the end of the drawer side is another story. The holes are easy if you have a precise indexing method, but cutting the scallop with sharp valleys between each moon is a mystery to me.
How did the machine actually do this? The information even in the patent is sketchy.

I posted this on the original forum too.

The link in Loren’s comment led to a photo (engraving) that gave me a hint. I wish there was a better photo or detail. Since this machine operated on an indexing pawl driven plate, uniform spacing was the only option. In addition, it appears that drawer heights were predetermined as a multiple of the index unit. It is an interesting challenge to consider how to build a (sort of) practical shop jig that mimics the original joint in all its crispness. The modern compromise loses the crisp points of the moon in the scallop.


-- Dan Krager, Olney IL One should always prefer the probable impossible to the improbable possible.

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10260 posts in 3612 days

#4 posted 10-13-2012 05:50 PM

The machine in the patent drawing appears to have two interchangeable
cutterheads, each with more than one spindle. It appears to plunge into
the work. and drill the parts. There are index holes in the machine.

The question of how the sharp inside crescent corners are cut is
vexing. Perhaps a small diameter drill defines the point and the
joint was finished by hand.

In the well-equipped factory the sharp points could be cut on
another machine, a shaper with perhaps an 8” tall cutterhead
with scalloped cutters.

Alternately, the same index hole spacing could be used to guide
the work over a pointy, router bit type cutter to finish the crescents
or perhaps cut each valley in its entirety, like the Legacy milling
cutters sold by Magnate.

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1062 posts in 3030 days

#5 posted 09-28-2016 12:33 PM

Dan, did you ever take this any further??

-- ***Pat*** Rookie woodworker looking for an education!!!

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5 posts in 2165 days

#6 posted 09-29-2016 10:53 AM

One of the things I thought at the time was that the drawer sides might be cut with a shaped knife or combination of knives. They were usually made out of a softwood so that shouldn’t prove too difficult. If you find out any more please let me know. I’m still interested if not interesting.

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