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Cutting a Tenon on a Timber

Started by Jim_Rogers, July 13, 2004, 04:11:10 PM

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Jim_Rogers

To understand how we've got to this point you might need to read the stories called "Using layout tools" parts 1 threw 5b in the thread labeled: "Tools for Timber Framing List".

It is from the end of that last section that we're picking up the next step in using tools and cutting joints.

Cutting a Tenon on a Timber[/b]
Part One

Personally I like to layout all the lines I can before a make any cut on any timber. I layout all the joints on both ends of the timber and any other mortises in between, first. Then once I've seen that all the joints fall in locations where there aren't any defects or bad knots and that everything looks ok, I'll start cutting on one end.

A timber that has had all possible lines drawn on it, without any cuts being made will have an end that looks like this:




 
What I do first is make the end of timber or end of tenon cut. This cut isn't that important to be exactly on the line, so we don't score this line first. The end of the tenon is sometimes cut back to make sure it doesn't bottom out in the mortise. Or in the case of a threw tenon, that it doesn't stick out beyond the timber to affect the siding.

If you have a small timber like a six by six and a big saw like a sixteen inch skill saw you can cut the timber off in one cut. But most timber framers will use a standard seven and one quarter inch skill saw. If that's the saw you have you'll have to make cuts on all four faces and then finish cutting off the end block with a hand saw.

When you do you'll have a timber that looks like this:

 



Then you draw the three lines on the end of the timber. One for each side of the tenon and the other one is drawn to make the tenon the correct size. And then you can X-out the waste wood. You should have a timber that looks like this:




 
Now that we have our tenon end all laid out and all the waste had been marked with "X's", we can begin to cut this tenon to size.

In the previous photos of a student laying out a tenon on the end of a beam, he had already cut off the end of the timber before he had done any of his tenon layouts.

We've been considering whether this is right or wrong. I was taught to do the entire layout of all the timber first because if you see something you don't like and you need to move the location of the end of the timber to allow for a change, and you've already cut the timber, you could have a problem. If you're going to make the timber smaller it's ok, but you have to be very careful if you cut your timber first.

After you have cut your end of timber cut we next start by rolling our timber over a placing the side that has the open arrow on it up, like this:

 



In this example drawing the tenon is a two inch tenon. It is laid out two inches off the layout face, on an eight by eight timber.

In this position the first section we will cut off will be the piece that will establish that the tenon is two inches off the layout face.

The first cut made is the shoulder cut; remember that all lines have been scored, first.

To cut the shoulder line and to be sure you won't cut to deep we set the skill saw blade depth by placing the saw on the timber and setting the depth of cut above the line, like this:

 



In the above photo the first side of the tenon has been cut but the principal for setting the saw blade depth is the same on either side. If the saw blade at its fully lowered position won't cut all the way to the tenon face line then you'll have to finish your cuts with a hand saw. More on using a hand saw later (in another story).

We can make this cut with a skill saw but we "leave the line" on all cuts. Then we will "pare" the shoulder to the line with a chisel.

Here we are starting the shoulder cut:

 



We will cut all the way across this shoulder line, leaving the line and score mark until the arbor of the saw blade lines up vertically with the outer face of the tenon. Then we do not move the skill saw until the blade has completely stopped rotating.

 



In the above photo you can see that the saw arbor is just about over the outer face of the timber and this will give us the maximum depth of cut all the way across the timber.
(Note once the blade has stopped and before we set the saw down, we release the rubber band holding the blade guard open).

After we have cut the shoulder line, we usually chisel off the waste using a large two inch chisel and a mallet.

The way I would do this is to take off large chunks of wood holding the chisel with the bevel side down. I start on a corner and then chisel off one corner and then the opposite corner and then the middle. This is done in several layers working my way down to the tenon side. As shown below:

 



I would start with the red line on the right, then the dark blue line on the left then the yellow line in the middle. Next the right pink line, then the left white line, then the middle light blue line. Like this:

 









I may do it a second and third time to remove as much waste wood as I could before I begin to "pare" to the line.

 



As you are removing the waste wood in these layers, you watch how the wood is splitting and see which way the grain is running. If the grain is slopping up, you should be ok; if the grain is straight with the tenon face you should also be ok. But if the grain is slopping down into the tenon you have to be very careful and do not remove to much wood and split down into the tenon and weaken it.

Now the side line had been scored with the knife and you should be able to put the chisel tip, with the bevel side up this time, into this line and carefully remove just a little wood from the tenon. The way I do this is to start on the right side and put about one eight of an inch of chisel tip into the cut and push the chisel from the tenon end towards the shoulder. If you have a good score line the chisel will follow the score line and open up a nice flat section of tenon. Like this:

 






 Then with this flat section as a guide, move over and take another small section off the tenon. As shown below:








Gradually working your way across the tenon to the left hand side. Now on the left hand side is a small section that is still waste wood and will be cut off later but we use the score line on that side, also. That way you have two scored lines and you connect them with a flat surface in between.

When you are done the tenon should look like this:

 



More in part two.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Jim_Rogers

Cutting a tenon on a timber[/b]
Part two


There are several methods to check your work to see if you've done it correctly and that you have the correct spacing. The first way is to hang your framing square over the tenon with the one and one half inch blade of the square up against the shoulder. Then sliding a speed square along the beam it should slide right over the framing square. If the speed square hits the faming square you have a little more to take off. Be careful not to take off too much.

 



Another way to check that the end of the tenon is correct is to set your framing square on the beam with the blade hanging down over the end of the tenon and check the tenon to the square and see if it's at the one and one half inch mark.

 


 
Also, with the framing square in this position you set your combination square to three and one half inches and place the flat side of the combination square on top of the framing square with the three and one half inch ruler sticking down towards the tenon. If the tenon pushes the combination square up off the framing square then the tenon isn't in the correct plane and need to be shaved off a little more.

 



Using this method you will insure that your tenon is cut to the correct frame convention, in this case one and one half inches off the layout face.

Then you roll your timber over and remove the waste wood from the other side of the tenon. Using the same procedures, we cut the shoulder line and then chisel off the waste wood.

This time as you near the score line you have to be careful not to cut the tenon to thin. We use a caliper tool to make sure the tenon is the correct thickness.

We set the caliper to the framing square like this:





This ensures that the caliper is set to the correct size of one and one half inch. If we were cutting two inch wide tenons we would set the caliper to the other side of the framing square, obviously.

Now that we have our caliper set to the correct thickness that the tenon needs to be, we can check our tenon:



 

As we have already established that our tenon is cut one and one half inches off the layout face we cannot cut any more off the layout face side, so we trim this side to make the tenon the correct thickness. The tenon in this case is one and one half inches thick. When the timber is softwood like this eastern white pine the caliper will leave scratches or scrape marks on the tenon. If you remove enough wood to remove these scratches you should have the correct thickness tenon.

When you are done you should have a tenon that looks like this:



 

Next we roll the bottom of the timber up and remove the last sections of waste wood and this will make our tenon the correct width for our frame convention.

 



The next procedure to do is chamfer the leading edge of the tenon. This will help it to slide into the mortise.





(The above photo is of a stub tenon that won't have the tenon side reduction done beyond the shoulder, but the chamfering principal is the same on all tenons).


The next step would be to layout and bore the peg hole.

That story will be in another post, soon.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Jim_Rogers

Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Max sawdust

Thanks for bumping this one up.  I enjoyed reading it again ;D

My absolute favorite "step by step" guide from Jim, is the one on cutting housed braces ;D
max
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bigshow

regarding the chiseling technique above...thumbs up!!! 

I never try anything, I just do it.

Jim_Rogers

Thanks, just passing on what I was taught.....
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Leo A

Wow- wish I would have found this awhile back- incredibly helpful stuff for us amateurs! Thanks

swmn

Yup.  I took the time on a recent vacation to go back to page one of this section and read all the thread titles on all 63(?) pages.  I opened about 20% of the threads while I was sitting on a beach; I got some sunburn while my wife was getting some Pina Colada. 

I know more 'stuff,' so hopefully my learning curve is steeper as I get to the doing phase.

One thing I have been working on is sawing the tenon shoulders like the furniture guys do their wee little tenons.  Then I can go straight to paring.

One caveat is don't use the same chisel for paring that you use for chopping.  It wastes a lot of sharpening time.  I have been 'paring' with my framing chisel, but finally bought a slick with a bit of belly and an acute bevel (~25 degrees) on it, and find it a huge time saver.  Same thing with furniture scale stuff.  You can use one chisel for both if you like (and want) to spend a bunch of time sharpening.  I guess it depends on what your time is worth.

FWIW 25 degree bevel on my slick in local softwoods works good for me.  I have no idea what bevel would be best for a slick if you are trying to pare a frame in hickory or white oak, wet or dry.

Second, drawing a bunch of lines on a scrap and sawing to them, knowing the piece is going to end up in the woodstove, means you don't have any real skin in the game.  I started making soap dishes.  Just get a little scrap of something maybe 1/2 to 1 inch thick about 2 inches wide and 1.7 x width for length.  Get that all prettied up to s6s.  Then on one side lay out lines 1/4" apart starting 3/8 inch off one edge.  Then flip it over and lay out lines 1/4 inch apart starting from the same edge so when you are done your kerfs will be staggered.  On the ends make a line 1/8" down from both faces so all your kerfs 'will be' 1/8" deep.

If you are practicing crosscuts lay out from the end.  If you are practicing rips, lay out from an edge.  Then saw to those lines and put that thing, warts and all, at the kitchen sink with a bar of soap on it.  I guarantee your sawing to the line will improve rapidly.

I made the last one with a ~1890 Disston 5 point rip that I sharpened myself with a bunch of set on it for green softwoods, in teak, and gave it to my wife for 'her' sink in the bathroom.  Took about 30 minutes for lay out and sawing.  My first two ended up in the wood stove as my skills improved.  Start with pine and then look for teak scraps when you got game.

NB: The biggest wood I have cut tenons in so far is nominal 4x6 Doug Fir labeled S-GRN by the WWPA.  I do have a locally grown spruce 8x8 out in the yard to bring into the shop for test cuts in a few weeks.  I will try removing waste from my tenon cheeks in 8x8 with both saw and framing chisel, but a fearsomely sharp five point rip moves through Doug Fir at +/- 20% MC wet basis in a big hurry with a slow stroke.

I do foresee that when cutting an entire building keeping the framing chisel sharp is easier than sharpening a rip saw.  The edge on the slick will have to be maintained either way.  The crosscut saw or electric circular saw will have to be maintained either way.  My 5 point rip is 28 inches, so 140 teeth to sharpen.  I can readily see that deep into cutting a frame just using the framing chisel to expose tenon cheeks for paring instead of stopping to sharpen a rip saw can make economic/time sense, but starting a build with a sharp rip saw makes sense too if you can saw to the line.




 


swmn

Crow sandwich with a side order of crow here please.

I recently had to rip cut a slab of KD white oak and I am pretty much done with rip sawing tenon cheeks.  I still think it is an alternative of last resort, but the more I work with sticks over 5x5 the more I want to rough out my tenon cheeks with a chisel.

To rip saw a tenon cheek, after the shoulder is crosscut most of us mere mortals will have to turn the post on the horses a quarter turn to make the first cut, then 180 degrees to make the second cheek cut, and then back a quarter turn for paring. Not so bad with furniture sized pieces, but when we are talking about an eight foot eight by eight it is a measurable number of calories and time just moving the stock around.

I did double check Will Beemer's book.  He mentions rip sawing tenon cheeks as possibly useful in especially wild grain or when there is an unavoidable knot in the tenon.

Thanks for the easy button way on this stuff Jim.

scsmith42

Great stuff Jim.  Brings me back to your tutelage here at the farm!

Thanks for sharing.
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