Getting rolling - dadoes, mortises and tenons

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Chris Hall
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Re: Getting rolling - dadoes, mortises and tenons

Fri Feb 24, 2012 5:56 pm

Continuing on now with the work on the internal partition joinery.

On my box, the top of the tenon is located 3/16" below the top of the dado. To mark out of the mortise inside the dado, I take a pair of gauge blocks and stack them vertically at the end. Then I push down with a chisel to define the top of the mortise:
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The tenons on the partitions I have set at 1" in height. I therefore add 1 more inch of gauging blocks to the pair already in place, then lay a gauging block into the dado and press the whole shebang tight:
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Then with the horizontal gauge block clamped in place, I pull out the vertical stack of gauge blocks and make a second chisel mark to define the bottom of the mortise:
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The sidelines of the mortise are 1/16" (1mm) in from the dado side walls, so I use a 1/16" gauge block to guide a marking knife along. The result:
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If you notice there are two upper lines knifed in - I had made an error with the spacing of the first mark, so I'm glad I double-checked before moving into cut out.

Speaking of cut out, these mortises are in the middle of the panel so my hollow chisel mortiser can't quite get to them. Over to the drill press then:
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Then some freehand chisel paring work:
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Once the mortise was cleaned up, I went and grabbed the 1:8 paring jig. In this case, the depth is actually 0.375" not 0.5". I could have recalculated and made another jig for a slope of 1/16" over a run of 0.375" (a 1:6 ratio), however I chose instead to just make one type of tapered wedge and in order to use a 1:8 paring jig in this case, all i had to do was move it slightly inboard of the line. I just did this offset by eye, however I use a square to make sure the edge of the jig is square to the board:
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Then I pared away the tapered mortise wall:
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This one is done, save for final fitting -see how the pared wall is slightly in from the marked line?:
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Some things I fuss more than others. I'm less concerned with very tiny differences in how the trimmed wedges may look on the surface of the board than i am about getting a good mechanical joint. If the difference was more pronounced, I would have made a separate paring jig.

Then i used a combination of router and table saw to process the tenons and so forth on the ends of the partitions:
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Finally, I decided to try a partial assembly to take a gander at how things were shaping up:
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For more on the trial fit and consequences, take a look at the thread 'Preliminaries: What Goes in the Box' where I'll delve in a little further...
djwong
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Re: Getting rolling - dadoes, mortises and tenons

Sun Feb 26, 2012 4:14 am

Chris Hall wrote: One minor detail - the end boards receive the floor panel end grain ends - there is very little seasonal movement to be expected along that grain direction, so the floor panel can be fitted a little shallower and with leas clearance space. While the side boards have a 0.25" dado depth, and the boards will insert to a depth of 0.1875", leaving 1/16" room on each side for the board to swell, the end boards have a dado of 0.2000" for the same depth of floor panel insertion, leaving a little less than 1/32" inch on each end to accommodate movement.
Chris, On the end wall dado being 0.2" deep, leaving a clearance of ~1/32"... Did you mean to say leaving a clearance of ~1/64" (1/64" = 0.156"), or should the dado be a tad deeper?

David
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Re: Getting rolling - dadoes, mortises and tenons

Sun Feb 26, 2012 11:02 am

Chris, On the end wall dado being 0.2" deep, leaving a clearance of ~1/32"... Did you mean to say leaving a clearance of ~1/64" (1/64" = 0.156"), or should the dado be a tad deeper?
Well, it looks like I have not been entirely consistent in listing my numbers for the dado depths, and as you've observed the math doesn't quite work there does it?.

I have made the dadoes 7/32" deep, which is equal to 0.21875", a hair greater than 0.2000". In either case, the intention is to make the depth of the tongue 1/32" (0.03125") less, to allow some room for seasonal movement - mostly for the expansion and contraction of the end board really. So, making the tongue 1/32" less than 0.21875 means a tongue which is 0.1875" into the dado. If the groove was 0.2000" deep, then the tongue would insert 0.16875". It's a difference of a hair more than 1/64" between the two set ups. On my box, I cut the groove to 0.21875 or so, and made the tongue 0.1875" long. Sorry for the confusion. I'll go back and amend that post accordingly.

~C
djwong
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Re: Getting rolling - dadoes, mortises and tenons

Thu Mar 01, 2012 1:55 pm

Chris Hall wrote:...I establish a central axis on the board and lay out to either side from there.
Hi Chris,
I am curious about this layout tip. Does this mean you draw a centerline down the face of the board and use the centerline as your reference to measure joinery location? I was going to approach layout using the top edge of the side and end walls as my reference. -Thanks, David
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Re: Getting rolling - dadoes, mortises and tenons

Thu Mar 01, 2012 2:44 pm

djwong wrote:
Chris Hall wrote:...I establish a central axis on the board and lay out to either side from there.
Hi Chris,
I am curious about this layout tip. Does this mean you draw a centerline down the face of the board and use the centerline as your reference to measure joinery location? I was going to approach layout using the top edge of the side and end walls as my reference. -Thanks, David
That's exactly what I did, and what I tend to do when layout is centered on a piece. It's not a critical thing however.

The main thing with layout in the case of working with jointed and dimensioned material is to establish a reference somewhere, and mark off from it. And be consistent. If you choose an edge, make sure you always reference from that edge, and not flip over to the opposite one every now and again.

The wider the board, the less accurate it tends to be to reference from only one edge, as the closer you get to the opposing edge the more potential for the marking tool to deflect.

If the jointed edge is good, and the end of the boards is square to the long edge, then the edge and end are a fine references.

If the edge was chewed up and couldn't be referenced, one could snap a straight line at some distance below it and use that as a reference. If a timber has a kerf cut in it down a centerline which made it impossible to snap a centerline, one would offset the line.

Choice of reference depends in part upon what tools you will be laying out with. If the edge is good on the board, then it is convenient to use a try square or combo square against that edge. If the edge was waney, say, then a square like that will be of no use and you would need to reference off of a snapped line and use a framing square or plastic drafting triangle.

If the board is bowed or curved and you wanted to use it, then the layout technique would be different.

Because my background is in Japanese timber framing, I am habituated to using a centerline reference for the most part. A centerline layout makes it easy to adjust for different thicknesses of stock. I also tend to use a combo square on a board having parallel edges, and then the square helps me auto-center my layout, even though I reference the tool to both edges instead of the centerline. I often measure out each way from a center line to define joinery locations, then perform a check afterwards measuring the total distance between points. If the mortise was 8" each way from a centerline, then the final check would be to see if the mortises were 16" apart, for example.

When measuring out from just one edge, where one measurement is placed further out then the next, a slight mistake in an early mark can lead to a ripple-down effect. The first mortise location is off by 1/16" and then all the marks are off - and the cluster of joints are not centered on the board. This may or may not matter depending upon how over-size the board is to begin with.

Regardless of what layout reference you choose to take, it is wise to check your marks afterward, preferably by measuring between the marks you have established, irrespective of the edge.
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Re: Getting rolling - dadoes, mortises and tenons

Sun Mar 04, 2012 5:53 pm

Mortises, tenons and dadoes laid out on sides, ends and bottom. I plan to cut the side and end dadoes for the bottom first then the mortised and tenons for the sides to ends. Since I am going to be using hand tools, my cut flow on the bottom and sides for the divider joinery will be a little different than Chris outlined. Following how it was outlined for using a power router and template gave me information on relating the cutting of the joinery for the dividers. I am going to cut and fit the mortises and tenons first and then adjust the layout lines to make the dividers relate to their dadoes. If the parts relate well to the layout lines then this will give me confidence that I could cut to the layout and then the parts would fit together. I'll have to see how it goes.

Side and end laying on full size drawing.
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Jack_Ervin.
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Re: Getting rolling - dadoes, mortises and tenons

Mon Mar 05, 2012 7:01 pm

Completion of the side and end board dadoes for the bottom. They went OK. They taught me a few things along the way. I started out dealing with them like a long shallow mortise going back and forth across to depth but decided that one trip across with a chisel then taking varying depths with a small hand router plane worked out better.
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Chris Hall
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Re: Getting rolling - dadoes, mortises and tenons

Mon Mar 05, 2012 7:15 pm

Looks good!
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Re: Getting rolling - dadoes, mortises and tenons

Tue Mar 06, 2012 6:44 pm

Well it's been more than a week and I guess its time to start rolling again. I was thinking there would be a few more people cutting wood by now, but I was thinking wrong! :) I'll just keep staggering ahead and hopefully won't lose anyone in the maze.

The next task I undertook was to dimension the end board tenons to their 0.375" width, which necessitated removing 0.0625" or so from each face. This I did with my router and edge guide. I was hoping to do it with my new Jessem router table, however there were delays in shipment and I only just received the machine today. There is more than one way to do the job, and a router table would have been better, but the alternative approach worked just fine.

I clamped the ends boards to a large piece of MDF so that the edge of the MDF could serve as a guide for the router:
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Once I had everything set up, proceeding with care and attention, the cut out didn't take too long. The result:
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The final step with the tenons is to kerf them on each side for the wedges. I marked out my kerf lines on the end grain, and then clamped the board onto the side of my planing beam:
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To start the cutting, I used an azebiki, working on the end tenon pair first:
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A little further along:
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Then I cut the opposing kerf:
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The kerfs are angled in slightly, not too much, not too little. The very last thing you would want to do with the kerf is have the cut line wander outward and inadvertently cut the piece of tenon right off or have it hanging by a thread. Almost as ill-advised, however, would be to angle the kerf on each side excessively inward so that the two kerfs meet one another at the bottom of the cut, in which case a internal wedge of wood would fall out and the tenon ruined. Keep the kerfs at a slight angle, so that at the bottom the kerfs are spaced at least 0.125" (3mm) apart.

Then I repeated the process with the two tenons on the other end of the board:
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That left the long central tenon, and to kerf it, I switched to a dozuki rip saw:
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if you lack an azebiki and a dozuki rip, have no fear. The cuts can be done easily enough with a standard ryoba - just make sure you use the rip side. A smaller saw is better here, say 180mm, so as to leave the desired narrow kerf.

The completed kerfed tenons. The process was then repeated on the other three board ends.
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In other news, I have prepared some stock for the upper lift out tray. The sides of the tray are quartersawn American Sycamore, while the floor panel will be Pau Amarello (Euxylophora paraensis). I'm wanting to use light-colored woods for the interior parts of the box where convenient.

Here are the pieces sitting ready, and still slightly oversize:
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I then glued up the tray floor panel:
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All for today, over and out.
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Re: Getting rolling - dadoes, mortises and tenons

Tue Mar 06, 2012 7:20 pm

I have accomplished hand routing the dadoes for the handles in the end boards.
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I'll be working back and forth on this and the roof model for a while.

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