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How do I keep tusk tenon wedges from coming loose?

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Forum topic by Adam D posted 872 days ago 4301 views 0 times favorited 23 replies Add to Favorites Watch
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Adam D

80 posts in 875 days


872 days ago

Topic tags/keywords: tusk tenon tusk wedge joints

I’ve only been doing woodworking for about 1.5 years, but thought I’d tackle a big dream of mine: MY BED. I plan to post more of this project later, but for now, how do I keep these pesky tusk tenon wedges from coming loose?! I used an angle of 10 degrees for the mortise/wedge. I think one of my mistakes was coating the wedges with wax…I thought this would prevent scratching up the legs as I pounded them in, and also to prevent squeaks—this is a bed after all ;-)—but now they’re coming loose every 2-3 days!

I don’t want to use glue because I anticipate it needing periodic tightening to account for seasonal changes, and I’d like to be able to disassemble it someday, hence the tusk tenons… What can I do to make them stay put? Maybe a dab of sealcoat or something? Hot glue? A little fold of sandpaper? ...maybe just clean off the wax?

-- Adam, Rochester NY


23 replies so far

View stefang's profile

stefang

12591 posts in 1935 days


#1 posted 872 days ago

I’m no expert, but I think a wedge has to be 5 degrees or less to work properly, and yes the wax isn’t a good idea.

-- Mike, an American living in Norway.

View Loren's profile

Loren

7257 posts in 2249 days


#2 posted 872 days ago

You can pin the joints. Either through the tenon or through
the bottom of the wedge.

Next time look at using less of a taper.

-- http://lawoodworking.com

View Adam D's profile

Adam D

80 posts in 875 days


#3 posted 872 days ago

I used 10 degrees because my “Woodworker's Guide to Joinery” book said to! Page 145! Did they steer me wrong?? O_o

-- Adam, Rochester NY

View rusty2010's profile

rusty2010

125 posts in 1159 days


#4 posted 872 days ago

I concur with stefang. The only fix I can think of is a pin below the wedge as it passes through the tenon or a new wedge

-- check, recheck then check again

View NathanAllen's profile

NathanAllen

376 posts in 1745 days


#5 posted 872 days ago

Same principle as a drawbore pin, less degree and have the top be wider than the mortise.

Good news is a couple easy fixes, cut a new set of keys at a 5 degree angle. Not sure if you have a 10 degree slope on the inside of the mortise, that may need to be adjusted to fit the new angle. Remember you want maximum touching between the key and the mortise.

View Adam D's profile

Adam D

80 posts in 875 days


#6 posted 872 days ago

Mannn, that’s the last thing I expected to hear—I figured literally going by the book (see link above) would rule that out, and you guys would just agree with one of my hunches (clean the wax off, dab of shellac, etc).

I don’t like the idea of pins—that eliminates the option of tightening them in the future, unless I make new holes each time…seems ugly. New 5° wedges would require me making some sort of FILLER wedge which I’d have to glue in there? Again, sounds ugly…

I took some alcohol to the wedges tonight to clean off the wax, and I’ll post in a few days to see if it worked. If it doesn’t, I’ll try some sandpaper and/or a drop of shellac in the mortise to see if that helps. Absolute worst case, I’ll use some hot glue—hopefully that’ll come loose the day I need to take it apart.

HOPEFULLY I won’t need to do the invasive surgery you guys have recommended! ...not that I don’t appreciate it of course, it seems a bit drastic…maybe I’m just in denial haha

-- Adam, Rochester NY

View waho6o9's profile

waho6o9

4749 posts in 1178 days


#7 posted 872 days ago

Put a dowel through the center of it.

View BobLang's profile

BobLang

96 posts in 2001 days


#8 posted 872 days ago

Try mineral spirits to remove the wax. The angle is a bit steep, but I’m thinking the wax is most of your problem. The drop of shellac isn’t a bad idea, I would use a drop of good old yellow glue. It will break loose if you tap on the bottom of the wedge to remove them.

One other thought, did you drive them firmly into place? You should be able to hear it when they are firmly in place. Don’t drive beyond that point or you can break out the end of the other piece, but you do need to get them seated.

Bob Lang

-- Bob Lang, http://readwatchdo.com/

View rusty2010's profile

rusty2010

125 posts in 1159 days


#9 posted 872 days ago

I agree with you on not wanting to add a pin. I done the same thing you did and ended up making new ones at 5 degrees. On that project there where 4 wedges each on 2 tables. Not fancy like yours tho.

-- check, recheck then check again

View Sylvain's profile

Sylvain

536 posts in 1101 days


#10 posted 872 days ago

It looks very nice.

Is the mortise long enough?

See :
http://villagecarpenter.blogspot.com/2008/06/tusk-tenon.html
to know what I mean.

The wedge must only bear on the external wall of the mortise on one side and only on the leg on the other side.

Otherwise there no pressure to ensure friction. And without friction it will come loose.

-- Sylvain, Brussels, Belgium, Europe - The more I learn, the more there is to learn

View Adam D's profile

Adam D

80 posts in 875 days


#11 posted 872 days ago

Sylvain: I overcut the mortises by about 3/32” (2.5mm) on the side nearest the leg to ensure that the wedge would fit tight against the leg.

I cleaned the wax off yesterday, and they’re still looking good this morning, so hopefully that was most of the problem as BobLang suggested. Time’ll tell.

-- Adam, Rochester NY

View kikkicurio's profile

kikkicurio

7 posts in 827 days


#12 posted 827 days ago

Hey Adam, an unrelated question in regards to this post. I am a design student with very limited woodworking experience and wondered if you could help me. I intend to utilise this joint for one of my own projects and I wondered what proportions you have used? Most guides and examples of this joint, show it being used with rectangular pieces of wood. Like you have done in this project, I would like to use it with squared pieces of wood. 60mm squared with a central tenon which is 20mm squared. How far should the tenon extend and what are appropriate proportions for the wedged keys? Is 20mm squared too thin and small for the tenon and will it cause me problems?

-Kiara

View Adam D's profile

Adam D

80 posts in 875 days


#13 posted 827 days ago

Kiara, if you’ve read the above posts, you’ll quickly realize that I’m not the guy to ask haha. Apparently even following the textbook instructions is sometimes wrong. That being said, my opinion is 60mm squared with a 20mm tenon should work fine. I’d guess the tenon would extend maybe 20mm past the face of the joined board. My book says you should use a 10° angle on the wedge, but the guys in this post insist that 5° is the magic number. I’d say that the bottom of the tenon should be no less than 8mm when it leaves the tenon since there’s potentially a lot of force on there.

BUT, I’m no expert by any means—I’ve only been woodworking for about a year and a half.

-- Adam, Rochester NY

View kikkicurio's profile

kikkicurio

7 posts in 827 days


#14 posted 826 days ago

Thank you so much, your advice has been invaluable. :) One and a half years experience, is one and a half years more experience then me.

Your diagram was extremely helpful. Now just to be tricky, after doing some tech drawings, I decided 60 by 60mm was too chunky and I now want to go with 50 by 50mm. The resource I am using says that you should never cut a mortise that is more then one-third the width of the stock you are working with, however, I want to maintain the 20 by 20mm dimension of the tenon. Am I pushing my luck?

I also wondered if you had any general tips on appropriate tools for cutting out mortises, creating tenons and most importantly, because I think this is what I will find most challenging, cutting the mortise for the tenon key? How do you cut accurately on an angle? I have access to a great workshop- so any shortcuts using powertools would be welcome.

View Adam D's profile

Adam D

80 posts in 875 days


#15 posted 826 days ago

On my bed (in the picture at the very top of this thread), the width of the tenon that passes through the leg is 29mm, and the width of the leg that the mortise is cut in is about 60mm, so 1/2…I haven’t crashed yet haha. I’d agree that the width of the WEDGE (key) should be about 1/3 the width of the tenon. No single rule applies in every situation. If you use the 1/3 rule and drive a tank over your furniture, it’ll still snap. Follow your gut—YOU’RE the designer.

My profile picture shows me doing just that—cutting the mortises for my tenon keys (I keep calling them “wedges”). I use a delta 14-600 mortiser (made in england, not china!) to cut all my mortises. Some mortisers tilt—mine doesn’t. I tilted the work piece instead by resting it on a 10° platform I made (just a piece of wood screwed to one side of another carefully-sized piece of wood—use your trigonometry!). You might have issues finding a hollow chisel for the mortiser that’s the exact size you want. I can’t afford to be too picky, so I just sized my wedge to match my chisels :-)

As far as cutting all the tenons and general shop technique, I learned a LOT from hours and hours of watching Norm Abram in “New Yankee Workshop”. Depending on the size of my stock and/or the tenon, I try to use my table saw with my delta 34-182 tenoning jig. On the long stock on my bed, though, my ceiling got in the way, so I had to use my band-saw and clean them up with scrapers.

I’d recommend making a “practice piece” of whatever you’re making, since you WILL have mistakes, especially this early in your woodworking career ;-) That being said, what are you making?

-- Adam, Rochester NY

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