wedged mortise and tenons guidelines?

[dan sherman]

does anyone know of any guidelines for determining the mortise relief angles?

[Pam Niedermayer]

does anyone know of any guidelines for determining the mortise relief angles?

OK, I'll bite, what are "mortise relief angles?"

Pam

[dan sherman]

OK, I'll bite, what are "mortise relief angles?"

I'm probably no using the correct term (still a newbie), hopefully the attached image will help clarify what I'm asking.

I'm designing a mallet to drive my soon to arrive chisels,and while doing research it looks like almost everyone uses a wedged mortise & tenon joint to hold the head on the handle. I also noticed that everyone makes the mortise like a dovetail (for lack of a better term), but never really specifies the angle.

Thus is there some kind of rule of thumb to help determine the angle, or is just trial and error?

[Frank Drew]

Dan,

You don't need much to make a tight fit; too much can be too much and risks splitting the handle. Your picture looks about right; another degree or two wouldn't hurt.

[Pam Niedermayer]

Are you buying socket chisels? Tanged? Both?

Pam

[dan sherman]

Are you buying socket chisels? Tanged? Both?

I'm getting some of these

http://www.leevalley.com/images/item/woodworking/chisels/10s0915-dsp.jpg

[David Gilbert]

Fine Woodworking had a pretty comprehensive article on wedged M&T joints.

Here is the link. Of course you need to subscribe to FWW's website. It was originally published in #124 (May/June 1997)

http://www.finewoodworking.com/SkillsAndTechniques/SkillsAndTechniquesPDF.aspx?id=2472

Cheers,
David

[Danny Thompson]

According to the FWW article linked above, go with 1:7 give or take (1:10 to 1:5) depending on the wood.

[Robert Rozaieski]

The angle for a through wedged tenon does not need to be much. The nature of the joint will make disassembly near impossible even with just a slight relief on the wedge side. I certainly wouldn't make the angle as severe as a dovetail angle for fear of splitting the part being wedged before it was spread far enough to fill the mortise. The harder and more brittle the wood being wedged, the more chance of this occuring at wider angles. I'd probably stick with just a slight relief, maybe a couple of degrees, but that's just me.

[Eric Brown]

Should the wedge be of an angle similar to the mortice taper?
Slightly thicker so it doesn't bottom out?
Should a hole be drilled across the bottom of the slots to better prevent breakage?
Should the wedge be quarter or flat sawed?
Could the wedges be put directly between the mortice and tendon?
Can the joint be dry fitted with wedges?
Are wedges better than drawbores? Both together?

Just curious.

Eric

[harry strasil]

FWIW, the weak part of that joint if its a handle for a mallet is the square shoulder, that's why a metal hammer head has an oval eye with both sides slightly larger to keep the head on the wood handle and the handle has a gradual taper as the constant stress of pounding will break the handle at the sharp corner.

http://img.photobucket.com/albums/v81/irnsrgn/smithing/hammereye.jpg

In my younger days, I had to watch myself and not get mad when using a smith hammer, as I could hit hard enough to break the handle off at the head if I didn't hit the work fair and square. ie, hitting on the heel or the toe would cock the head enough that the shear force of the blow would twist the head enough to shear the handle.

[Robert Rozaieski]

Wedges should be slow tapering. Fast tapering wedges will tend to be pushed out of the slot. You want it to almost bottom out when fully driven which means that when test fit it will not go in all the way. Think shim more than wedge. Long slow taper. This is why the relief angle of the mortise shouldn't be too much. If the mortise relief is wide, you would need a very short fast tapering wedge to spread the tenon completely. You're not trying to make a joint that looks like a dovetail, just something that is more or less slightly swelled on the wedged side.

FWIW, when I made my plane adjusting hammer, I chopped a straight mortise to begin. Then I just made an angled paring cut on each side of the mortise from what was to be the flared side of the mortise to the narrow side. I took off maybe between a 16th and an 8th of an inch on each side of the flare. When I attached the handle, I used two long, slow tapering wedges. This was a small hammer so for a mallet with a thicker head I would probably pare between 1/8 to 3/16 on each side of the flared side.

[harry strasil]

This is what happens to a piece of iron when you use a scribe to mark a bend line. Iron, wood and glass are alike when you have a sharp corner at a stress point.

[Pam Niedermayer]

I used a screw for the last mallet I made, made the threads with a 3/4" tap and screw box, worked great for quite a while. The mallet head split a little, but that was a function of having used pine.

Pam

[Frank Drew]

Should the wedge be of an angle similar to the mortice taper? Yes, the included angle (both sides).


Should a hole be drilled across the bottom of the slots to better prevent breakage? I've drilled a hole at the end of the kerf for that reason, and the pieced didn't split, but I can't say for sure that the hole made the difference.

Should the wedge be quarter or flat sawed? With such a thin piece of wood I don't think it'd make all that much difference, but if you had a choice, quartered, probably.

Could the wedges be put directly between the mortice and tendon? I think that wouldn't lock in the tenon, if I understand your question correctly.

Can the joint be dry fitted with wedges?Definitely, you'd want at least one practice fitting, but not all the way and with the wedge still long so you can grab it to loosen and disassemble the joint; get it close and you'd see if it'll go all the way home when it's for real. A tricky joint, however, is the closed (or blind) wedged tenon, where the wedge bottoms out in the mortise just as it spreads the tenon the correct amount; obviously, that can't be dry fitted because once it's together that joint ain't coming apart.

Are wedges better than drawbores? Both together? I wouldn't use both; it's overkill and risks either weakening or splitting the wood. (IMO, drawboring is more appropriate for timber framing, where no glue is used, than for cabinetry or furniture.)

[Jeff Johnson]

You're over-thinking it, worrying about the angle.

Bore your hole first, file the shaft with a mill file so that it goes in tight by hand (with the handle in a vice and some hard twisting) and file about a sixteenth of an inch from the front and back of the hole, tapering all the way down through the head.

Then split the handle crossways with a narrow bladed saw, insert handle, insert wedge, & tap it in solid. Oil it up a couple of times and everything will swell even tighter.

[David Keller NC]

Should the wedge be of an angle similar to the mortice taper?
Slightly thicker so it doesn't bottom out?
Should a hole be drilled across the bottom of the slots to better prevent breakage?
Should the wedge be quarter or flat sawed?
Could the wedges be put directly between the mortice and tendon?
Can the joint be dry fitted with wedges?
Are wedges better than drawbores? Both together?

Just curious.

Eric

Eric - couple of comments/opinions that might differ a bit from what you've already heard.

About the placement of the wedges relative to the tenon/mortise: To do what the wedges are intended to do, you must split or saw-kerf the tenon. The purpose of the wedges is to distort the end of the tenon into a dovetail shape that matches up with the tapered mortise, thus locking the joint. There are various ways to kerf the tenon - some drill holes at the bottom of the kerfs to prevent the possibility of the split in the tenon continuing through the joint and into the stile/rail that the tenon's on the end of. Some of us simply assemble the tenon into the mortise, and use a chisel and a mallet whack to split the end of the tenon in two places to accomodate the wedges. Personally, this method's always worked for me without disaster. However, there are some caveats.

One caveat is that the splits put into the end of the tenon must be close enough to the edge of the tenon so that the portion that will be bent by the wedge is flexible. Typically, that can be anywhere from 1/16" thick to 3/16" thick depending on the species of the stile/rail, the size of the tenon, and aesthetic considerations. Also, for the chisel method to work well, the grain in the stile/rail must be pretty close to parallel with the length of the stile/rail close to the end with the tenon. If the grain "runs out" wildly near the end of the tenon, the chisel split may actually split off a wedge of the tenon completely. Even if you saw kerf the tenon, if the grain runs out the insertion of the wedge and drving it home may break the tenon. This is a point often glossed over in videos/mag articles about wedged through-tenons.

Another caveat is that the risk of the split running into the stile/rail from the tenon is higher the greater the wedge angle/mortise taper is. However, this is a trade-off - higher wedge angles applies more locking force to the stile/rail and tenon. Generally speaking, I use wedges that are about 7-11 degrees in my shop.

Finally, realize that you don't have to drive the wedge all the way to the base/shoulder of the tenon, nor do you have to taper the mortise all the way through the piece. Tapering it 3/4s of the way through will still lock the tenon very securely, will still be attractive from the show side, and means that you don't take the risk of splitting out the case side on the back side by an inadverdent paring stroke of the chisel.

[Eric Brown]

The information you provided will be useful.

Eric

[Jim Koepke]

My bought mallet has a tapered handle and a tapered mortise to match. There is no wedge.

My mallet that copied the "store bought" mallet taught me to not cut the end of the handle flush with the top of the mallet. The handle has pulled down into the head about an 1/8 inch.

jim

[Dan O'Sullivan]

Its funny I bought the smaller set of Narex(made in Czech) chisels to use as beaters. After a little tuning up they were sharp. What has impressed me most is how well they hold an edge? Its amazing. I looked into the chisels after reading C. Gouchner's review in FWW and I'm impressed with them. Hope you like them. The price is right and the steel is good.

[george wilson]

Do not think that Narex makes only cheap chisels. I have a universal boring head set by Narex that costs about $2500.00. It goes on my milling machine to single point bore straight or tapered holes,or to feed straight in and out,to form "bosses" around the top edges of holes. It is top of the line.

[dan sherman]

A lot of the eastern European countries get a bad wrap for some reason, I have some Bison (Polish) metalworking tools, and they are top notch.

[george wilson]

I have several Bison chucks on both of my lathes. Lately,they have gotten much more expensive than they were. In the past 2 years they have greatly increased in price.My favorite chuck is my 8" 4 jaw universal Bison chuck. It holds true to .001",and you can hold rounds or squares in it without changing chucks.

[David Myers]

Chris Schwarz wrote an article entitled "Why Wedge Tenons?" in the Autumn 2006 issue of Woodworking Magazine.

He discusses the typical kerfed approach, but also notes a kerfless one (he credits a chairmaker named David Fleming for showing him the method). Essentially you introduce a small split in the tenon after the joint is assembled and glued. Then you drive the wedge into the split. He endorses this method for looser joints (1/8" on either side of the tenon).

The article has very nice cut-away views of the various wedged joints (kerfs, kerfs with holes, etc) and an approach for making the wedges.