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A couple of years ago I was examining a German microscope case and noticed that the finger joints were angled. I realized that this was an interesting and useful idea, and probably this made this joint superior to any other right angle joint I could think of including the dovetail.
Firstly the angles would keep the joint from hinging and thereby reduce the unbelievable amount of clamps needed for normal finger joints.
Secondly the angles would give the joint a mecahnical advantage in that the shape would not allow even an unglued joint to seperate, at least from one vector.
Thirdly the large number of “combs” would present an enormous glue surface.
Has any one set up and cut this joint? If so how well did the set up go and were you happy with the results. BTW this box was made at the latest in 1947 and more likely well before that.
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I've watched this question for a while, and no answers yet! I'm curious too. Could you maybe do a sketch, scan it, and post a JPEG. Perhaps you don't have a scanner? It's surely not this joint, the double twisted dovetail as attached, is it? Sliante.
*Sgian, I knew eventually you would not be able to resist an empty post! :-)Your lovely photo is similar to the joint I am referring to except that fingers are of the type of spacing you would find in a finger joint and all the fingers on the board "lean " in the same direction. I could do a CAD drawing but you would need a program that can read a DXF file, I could also convert it to a jpeg but it would come out pixelated. The joint is just like a finger joint except the fingers "lean" at about 8º. the bottoms of the negative fingers are parallel to the edge of the board...... so that if you angled say a dado blade, or a router bit you would not get a flat bottom and the joint would leave a gap.
*Sgian, I converted this VEL format drawing to a Jpeg and then a Gif. Sheesh, I hope it works last time it didn't.
*Well, I can only think of one logical way to cut this joint, bearing in mind the historical period and the safety regulations applicable at the time in Europe; set a dado type blade to the appropriate depth, and a mitre gauge to 8 degrees to cut one half of the joint on a table saw. The other half, the bit that has the matching fingers all angled the same way, would require a special blade with a cutting edge that is angled at a matching 8 deg., along with tilting the blade to 8 degrees, as well as exactly matching the thickness cut by the first blade, and then passing the end of the board over and perpendicular to this blade. But this still seems wrong somehow, for how do you match up the appropriate waste cut to the bit that stays. I can see how this might work, but I'm not convinced about the practicality of it in my own mind. I guess I'm just thinking out loud, and if I get truly inspired, I'll get back. Perhaps someone else has some bright ideas? Sliante.
*Sgian, I've been thinking about this too and my guess is that a shaped dado was used, in that the top of the blade (the rakers) were cut to be parallel to the table in spite or the fact that the blade was angled. This along with a angled gage. I'm tempted to take this joint apart to help my brain get wrapped around and figure it out how this joint was cut. Knowing the Germans it could have been a stack of precision dadoes, engine divided to do the spacing....... Nah that doesn't sound quite right either.
*Apart from cutting it by hand of course, as is the joint illustrated in my post 1.1.. No machine invented yet that can successfully replicate that one commercially. Perfectly do-able (by hand) of course, but this method doesn't seem right in this case for what is most likely a machine cut joint! Sliante.
*Sgian;After looking at the image you posted, I must admit I can't see how to assemble the two halves of this joint. Seems there is interference no matter how I look at it. Beautiful work.rexp
*Nice of you to say that Rex. Here's a graphic of the joint cut ready for assembly. The rises are rather exaggerated for clarity. It's one of those joints that is assembled once only if you want it to go together cleanly. It's also a one shot deal. It's either cut correctly, or it's scrap!! Sliante.
*Indeed Sgian, this is almost certainly a machine cut joint not only because of the engine-like divisions but because the microscope itself is a mass produced item.(Ernst Leitz Wetzlar No.382567) The case has slots and fittings for this specific microscope, so I am sure they came together.This may be a hint ..... the hinges have rounded corners and are set into a hinge mortise that is likewise rounded, as if cut by a router, same with the strike. Also there is a mount for some missing accessory that is cut with a T Slot type of bit.I don't see how this could be cut with a router bit but I'm still leaning toward the shaped dado blade theory. I can see how a router bit would be able to cut the slot, both the "lean" and the angle but it could not make the bottom of the cut parallel to the end of the board.
*Wow, a very impressive joint-beautifully cut. The joint I'm trying to describe is like the second joint from the right.My original post erred in that the joint will resist pulling apart in two vectors, and must have been put together from a third vector in line with the "lean". Much like your joint. This is great for taking advantage of the mechanical strength of this joint because the box is rarely, if ever subject to a force pulling at it from 8º.
*It's an interesting photo of dovetail work. Cut by any means, it can't be pushed together. It's either inlaid veneer or painted. I assume we're all looking at the same photo. It's like the Loch Ness Monster. I've seen this photo off & on again for years. Look at it. You can cut each side. It's just a compound mitre. Connect the dots & cut. But you can't push them together. Try it. Plan each piece. Cut it. It can be cut, but not fit. Try it rough & then try to slide it together. Don't waste a lot of time on this. If it looks too good to be true it probably is. Next riddle? Ken 631-738-9097
*Are you refering to the photograph of my joint, what I call the 'double twisted dovetail'? If so, all the points made in your post are incorrect. It can indeed be cut and assembled, and it's not an optical illusion. I have plenty of examples that can be viewed. Would you like to set a date? Sliante.
*Sgian,I'm sorry. I don't mean to be insulting. Looking at the picture I see angles that appear to be impossible to push together. I'd love to be shown how you can do this double twisted dovetail and become a believer. Thanks, Ken
*Ken, Failing a visit to my workshop for a demo., the following jpeg's are the best I can do. From now on I presume you'll be a believer? This is technically the single most challenging joint I make. There is no room for errors, as exhibited in this sample I made for an article. I'm afraid you'll have to scroll through successive posts to work through the logical sequence. i couldn't seem to attach more than one illustration per post. Why does your name seem familiar? Sliante.
*Sliante, I can see how you do it. It's cut to push together as a mitre joint not as a box butt joint. I was thinking it must be mitred somehow. I'm on the go & need more time to contemplate your work. I'm in NY on Long Island but I travel a bit on the east coast as an old time country blues musician. Again I apologize for my initial observation. I am an old dog excited to learn new tricks. Where are you from as I'd love to visit your shop. I'll send photos of my work if I can figure out how to post them. Thanks Ken
*Sgian, Nice job. I would also like to learn this joint. Has the article you produced this joint for been published? If so where? If not FWW should take it on.TC
*TC, That's very generous of you to say that. Yes, I did write an article, and it was published in Woodshop News, August '98, and The Woodworker, a British magazine, volume 103, Issue 2, which I think was January '99. I think FW published something by Alan Peters that is either the same or similar, many years ago now. You might check with them. Sliante.
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