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Occasional Table Class (Hand Tool Build) #14: Mortise and Tenon

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Blog entry by RGtools posted 10-19-2011 04:20 AM 6814 reads 1 time favorited 30 comments Add to Favorites Watch
« Part 13: Using the tools: Lesson 1 the Winding sticks and Straightedge. Part 14 of Occasional Table Class (Hand Tool Build) series Part 15: Designing a table. »

Mortise and Tenon

Before we start on our table, we need to take the time to make a few practice joints. The oldest and strongest joint out there is the mortise and tenon. It’s also the only joint used in this occasional table.

I wanted to make a set of bents to show you this but the hickory I had on hand developed quite a few cracks that kind of killed that idea for this weekend (a total drag for me because I really wanted an excuse to make the bents). On the other hand it’s good that I could not do that because it may force you to take a look around your shop to see what you need that may require mortise and tenon joinery (workbench, bents, a drafting square for drawing…something that you can evaluate)

Failing that…a practice piece is a good warm up.

We will start with a piece of easy working wood (pine, poplar, alder…anything soft). Your dimensions should be in the realm of 3/4”, 2”, 24” (keep in mind the exact measurements are not important, just get close while removing the lease amount of wood to get square stock). Flatten a face, checking for twist, bow, and cup (this will be your true face…mark it with a squiggly), square an edge to it (true edge, mark it as such), plane to width and then plane to depth.

Let’s also cut the then ends off square so we can show you how to make accurate (and visually appealing) saw-cuts at the bench.

To cut the end of your board square, use a knife and a square to make a mark square all the way around the edge of your board (referencing the stock of your tool on you “true” face and edge…if it sounds like I have repeated that a lot it’s because it’s one of the most important things you can do to create decent handwork)

Right

Wrong

Use a wide chisel to deepen that line (wide chisels are easier to steer) and then make another cut on the waste side to create a “v”. This “v” guides the saw and creates a cleaner cut since the outside of the work has been cut with a chisel instead of a saw…this is one way you can get away with a rip saw on a crosscut.

Occasionally this will result in a saw whisker (yes I know the corners have the “v” notches in them…I did not cut them off on this one since I wanted to focus on the joint rather than the saw cuts)

Take this whisker off with a sharp chisel and a light touch.

For the ends of boards that need to be of an accurate length a simple knife line around the board and a notch to start your cut is plenty.

Saw this board in half on and square the ends for practice sake (make sure your have reference marks to denote your true face and edge on what will become your two boards). Today I’ll be making a corner mortice that you would be likely to see in a door, rebated back in a cabinet, or…a table leg and rail.

Make a mark on the true faces as shown so you know how the joint goes together, on a full fledged assembly the mark would not be on the joint (and not it pen), but this simplifies things for this project quite a bit.

On the piece with the point we will make our mortice. To start, make a mark on the inside edge to designate where the bottom of the tenoned piece should fall, this is the only mark you should make…unlike some people.

Use dividers to set the set back distance, this should be about a quarter inch to give strength to then end of the joint while not losing too much glue surface (set these dividers aside since you will need this measurement later). Make an indent with the dividers and extend that indent into a knife line (don’t make these very deep, or stop a bit shy of the edges of the board since a deep score mark could show on the outside of the joint)

Then you can use your marking gauge to locate the sides of the mortice. In a closed mortice I only make one line with my gauge since, the chisel itself defines the other wall. On a through mortice, the extra line is worth the effort since in reduces the chance of tear-out on the show side.

Once you have located the mortice, you can start cutting it out. I always make my first two chopping cuts about an 8th inch away from my scribe lines for the ends of the mortice. Because of the force of the wood on the bevel of the chisel, the tool will not drive straight down so excavating the depth of the mortice first then chopping the ends straight down at the last ensures accuracy (the 8th inch waste wood that you leave till the end also gives you a sacrificial leverage point to pull chips out).

I can also set a square next to my work to ensure I am cutting straight.

Clamp the work to your bench so it cannot move from the force of your chisel. On narrow pieces make sure to arrange your work so it’s supported enough to not fall over.

My procedure for getting a mortise excavated is as follows.

Make two initial cuts about an 8th from the ends, when doing this I tilt the chisel away from the joint a bit so it drives more straight. This cut never goes further than the bevel of the tool (trust me getting a chisel stuck in your work is not entertaining)

Lean on the chisel make light scoring cuts along the length of the mortise (minus the 8th inch on the ends that we will leave until the end). Clean these chips out to create a small (8th or so) trench, this is a great aid in locating the chisel during the “bash out” part of the mortise, and it reduces your chances of tear-out on the side of the joint.

Use the chisel with the bevel towards the higher side of the waste in the mortise and take small bites with the force of you mallet. The chisel will cut chips and because of the bevel will also break them into the empty part of the cut (waste you have already cut). Lift out these chips with the tool. As I get deeper into the cut I take bigger bites as I have past the worry of tear-out. Take care not to let the chisel twist during the process as this will create and over-sized mortise wall.

I make a mark on my chisel to give me an idea of how deep the mortise needs to be. A set of dividers and and combination square is useful to have on hand. Set the dividers to your tenon length and your combo square a bit longer so you can check that your mortise will receive your tenon without the tenon bottoming out. I tend to march back and forth across the mortise with my chisel until I am at depth but there are other ways to get to the same goal (aren’t there always). Double check this carefully to make sure you have reached depth across the entire cut.

Shear off the ends of the mortise and remove those chips careful not to dent the ends of the mortise. Recheck to make sure the depth is consistent and deep enough.

When laying out the tenon you can use the mortise to directly gauge from one piece to the other. Set pieces flat on your bench and set the tenoned piece against the mortised piece so you can access the mortise from the outside. Use a scribing knife to make marks on the tenoned piece using the mortise wall as a guide. Extend these marks to around the outside of the joint. The ideal way to do this is to have a marking gauge set to one wall of your mortise, and another set to the other wall, (this assumes you are marking from the face side each time) these two gauges left untouched could mark all your mortise and tenon joints for an entire project.

You can use the dividers you used earlier to mark the marks for your setback (the smaller waste material section of the tenon) and then extend those lines. You can imagine that it is a good idea to either mark all your pieces in a project in series, or have a ton of layout gear.

To saw out the waste I have tried several different approaches and I am still experimenting. Woodwork is best experienced from multiple perspectives, the more workable methods you try out the more our craft will make sense to you on a whole. For now, let’s saw the tenon cheeks first followed by the setbacks (the cheek is the part of the tenon that will slide into the mortise while the shoulder is the part that stops the work from sliding further into the joint). In the video I removed the cheeks first the cut the shoulders, then do the set-back cheek, main shoulder, then setback shoulders. This give you good viability and good registration surface with the saw. I switch up the order a bit in the video below but you get the idea..play around until you find something that makes sense to you.

For the cheeks I make a simple notch to start my cut, on my shoulders I cut the whole groove with a chisel before I start sawing.

For extra credit you can draw-bore the joint. Use a dowel (or even better whittle a peg to an even diameter) to force the joint tight and make in permanent. I wedge or draw-bore most of my joints because I don’t trust glue, and I like the permanence of it. Draw-boring is also cool because you can create assemblies without clamps. To achieve this affect drill a hole through the mortise piece in what you estimate to be about the middle of the tenon (do not have the joint assembled), it’s a good idea to have scrap in the mortise to prevent tear-out on the inside of the joint. Ice this hole is drilled assemble the joint and use your drill to mark the center of the joint on the tenon (the point on a brad point drill works well for this.). Teak the tenon out and drill a hole slightly more towards the shoulder of the tenon. When assembled the holes are slightly offset and the pin being driven through this hole forces the joint tight and makes and permanent. A few tips, take a pencil sharpener and ease the edges of the pin so it goes in more easily. Also when you are gluing up, make extra pins and put a bit of wax on them, this helps matters tremendously. Use a playing card with a hole in it to saw off the pin without scoring your work and then trim it flush with a chisel, or do the chisel trick as shown in the video (which works better on softwood pins than hardwood ones.)

When you are done you can saw out everything but the joint (saving enough material that you can evaluate or even mark your mistakes) this way you can continue making practice mortices while only using a few inches of the wood each time. Practice makes perfect, applied practice teaches you more quickly…find something.

-- Make furniture that lasts as long as the tree - Ryan



30 comments so far

View Brit's profile

Brit

5148 posts in 1496 days


#1 posted 10-19-2011 08:02 PM

RG – Once again you amaze me. I always cut my joinery by hand simply because I enjoy the challenge and although I do a couple of the steps slightly different, I basically follow the same process. Like you, I’ve experimented with different methods and I’m now happy with my process and get repeatable results. My process varies from yours as follows:

1) I use the mortice wheels on my Titemark gauge and set them to the width of my chisel. Then mark my mortice and the tenon with the same setting. I saw to the line and strive for saw cut to saw cut joints.
2) Before I start chiselling my mortice, I drill a full depth hole about 1/8” in from one end with a bradpoint bit, then I chisel the waste into the hole. Using this method you can go full depth from the outset and it is significantly quicker when you have a number of mortices to do.
3) I chamfer the end of my tenons very slightly and also the top of the mortice with a file. The reason I chamfer the tenon is that when it comes to the glue up, it is much easier to start multiple tenons when putting a project together. It also creates a little space for the glue that gets pushed down into the mortice to accumulate. I chamfer the top of the mortice slightly so that if glue does squeeze out the top of the mortice, there is a place for it to collect and it doesn’t squeeze out past the shoulders and prevent the joint from closing tightly or give me problems when I come to finish the piece.
4) You didn’t mention applying glue to a mortise and tenon joint, but nowadays I only apply glue to the mortice. If you put glue on the tenon and then drive it in, you are bound to get messy shoulders.
5) When drilling the mortice for drawboring, sometimes I don’t drill right the way through both mortice walls. Obviously you can only do this if you have enough thickness in the mortice walls, but there are times when I don’t want the dowel to show on the face side of the component but still want the benefits that drawboring provides. If you look at my breakfast bar project, you will see an example of this.

Thank you for all the time you are putting into this great class. I really appreciate it.

-- Andy -- Old Chinese proverb say: If you think something can't be done, don't interrupt man who is doing it.

View Brit's profile

Brit

5148 posts in 1496 days


#2 posted 10-19-2011 08:05 PM

Oh yeah, one other thing I do is put my dowels in an electric drill and lock it in the on position and use a file to chamfer the ends of the dowels.

-- Andy -- Old Chinese proverb say: If you think something can't be done, don't interrupt man who is doing it.

View RGtools's profile

RGtools

3302 posts in 1307 days


#3 posted 10-19-2011 08:09 PM

1. Do you use the fixed mortise wheels or the adjustable? I have been thinking about shelling out but can’t decide which way to go.
Love step 2. Will try that.
3. I do this as well on glue up. Missed it for this entry good catch.
4. when we get to glue up was going to cover, VERY good advice though so it will be worth repeating.
5. I will be doing this on my occasional table (mine is actually a simple desk) because I love drawbores, but the look just did not fit.

Thanks for these comments. There is so much to cover it’s good to have someone with experience to watch your back.

-- Make furniture that lasts as long as the tree - Ryan

View Brit's profile

Brit

5148 posts in 1496 days


#4 posted 10-19-2011 08:25 PM

All I have at the moment are the adjustable ones. I would like to get the fixed ones too, but they are pretty pricey for what they are and not a priority for me at the moment. Worth getting though if you often chop mortices of a set width.

If you send me a PM with your email address, I’ll forward a PDF of a great article I have on different ways to chop mortices where the drilling method is covered in detail. The article is well illustrated and looks at the pros and cons of each method.

I can’t claim to be very experienced RG, just well-read. :-) However, I am someone who thinks about why things are done in a certain way and I’m always looking for little tweaks to make a process more accurate and quicker, which is why I’m enjoying this class so much. You seem to share that approach to working wood.

-- Andy -- Old Chinese proverb say: If you think something can't be done, don't interrupt man who is doing it.

View RGtools's profile

RGtools

3302 posts in 1307 days


#5 posted 10-19-2011 08:51 PM

This is true. I think that’s one of the main things that attracted me to handwork. You can adjust on the fly.

I bet you could get away with just drilling one hole. I was thinking about it while I grabbed groceries. Can’t wait to get home and play.

-- Make furniture that lasts as long as the tree - Ryan

View Brit's profile

Brit

5148 posts in 1496 days


#6 posted 10-19-2011 08:56 PM

Definitely, one hole is all you need. Because the chips break off into the hole when you drive the chisel in, there is less resistance and it is less effort to chisel and easier on your tools. When the chisel reaches full depth there is a definite increase in resistance and you know to stop.

-- Andy -- Old Chinese proverb say: If you think something can't be done, don't interrupt man who is doing it.

View RGtools's profile

RGtools

3302 posts in 1307 days


#7 posted 10-19-2011 09:02 PM

You hear that everyone? Andy just struck on another salient point of handwork.

Listen to your tools, they tell you what to do. (that goes doubly for the wood)

-- Make furniture that lasts as long as the tree - Ryan

View mafe's profile

mafe

9509 posts in 1742 days


#8 posted 10-20-2011 09:56 AM

Another fine blog, once again you take us through the stages in a easy and pedagogic way.
I wish I had had your blog when I should make my first mortice and tennon, a picture says more than a thousand words and these little videos make it a lot easier also.
Way to go.
I am quite lazy, so I drill a series of holes on my drill press and basically pare out the waste when I do mortise.
For the tenon I saw app 1 mm on the good side of the line and pare the tenon clean after, this because I then am absoluteli sure to get a perfect fit (I have had my share of loose tenons due to my lack of saw skills).
Best thoughts,
Mads

-- Mad F, the fanatical rhykenologist and vintage architect. Democraticwoodworking.

View Don W's profile

Don W

15029 posts in 1221 days


#9 posted 10-20-2011 01:47 PM

I’ve never actually done a mortise and tenon completely with hand tools. The RAS just calls my name. My son also recently left his Delta mortising machine in my shop, so I “had” to try it out.

I agree with what you said “Listen to your tools, they tell you what to do. (that goes doubly for the wood)”. We all handle tools just a little different, and tend to work a little different. There may be a wrong way, but there are also many different “right” ways.

Thanks once again for the time to show us your way. After reading your blogs (and others of course) I tend to try different ways. I don’t typically completely change the way I do things, but will often modify some process as I learn new and different approaches. Its the beauty of woodworking. Maybe you can’t teach an old dog a new trick, but if one of the tricks is to keep learning, your golden.

-- Master hand plane hoarder. - http://timetestedtools.com

View RGtools's profile

RGtools

3302 posts in 1307 days


#10 posted 10-20-2011 03:08 PM

Thanks Mads, That’s the general idea. I had a saw skills primer that I really need to post. It’s one of those quick tip sort of things that really made a difference for me. I have had my fair share of loose joints too but it does not happen much any more (thank goodness). Later in the series I ought to go over some of the ways to fix your mistakes.

I could not agree more Don. I feel like I took a bit of “a my way is the right way” approach with GaryP, earlier in the series. I did not mean to but it was taken that way. I have since made it a point to change my tone. If I see something wrong I’ll correct it but other than that. I am going to try to encourage people to develop their own system that works for them.

-- Make furniture that lasts as long as the tree - Ryan

View Don W's profile

Don W

15029 posts in 1221 days


#11 posted 10-20-2011 03:22 PM

RG, what you are trying to do is difficult. Teaching is hard enough, but you don’t know if your reader will be someone who’s never touched a tool before, or an old timer that could cut circles around you. Its great that you can be flexible, but I’ve said it before, this is a great series. I’ve done my share of teaching (not woodworking, but still). You can’t write for everyone 100% of the time.

Keep up the great work.

-- Master hand plane hoarder. - http://timetestedtools.com

View mafe's profile

mafe

9509 posts in 1742 days


#12 posted 10-20-2011 06:06 PM

;-)

-- Mad F, the fanatical rhykenologist and vintage architect. Democraticwoodworking.

View RGtools's profile

RGtools

3302 posts in 1307 days


#13 posted 10-20-2011 06:38 PM

Thanks Don.

-- Make furniture that lasts as long as the tree - Ryan

View Brit's profile

Brit

5148 posts in 1496 days


#14 posted 10-20-2011 06:42 PM

Mads – Now you’re teaching me English. I had to look up pedagogic.

Jeg er imponeret. :-)

-- Andy -- Old Chinese proverb say: If you think something can't be done, don't interrupt man who is doing it.

View Don W's profile

Don W

15029 posts in 1221 days


#15 posted 10-20-2011 06:45 PM

Same here Andy.

-- Master hand plane hoarder. - http://timetestedtools.com

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