I’m building a Morris-style chair, and I have run into a problem with squaring the fit between the legs and side rails. For reference, the top rails and the bottom rails that fit into the leg mortises are parallel and the same length, and the tenons lengths of the top rails are 1 inch and the bottom rail tenon lengths are 2.5 inches.
I’ve dry fit the leg and side rail assemblies, and the inside corners of the assemblies are not square. I put the faces of the rail boards against each other, and they are slightly not the same length between the tenons. Also, the rail tenon lengths are slightly different, so I can understand why they are not square. But how do I fix this?
I can true up the tenons and the length between tenons of the bottom rails OR the top rails, but because the top and bottom rails that make up a side of the chair have different tenon lengths I don’t see how to make the distance between their tenons the same.
Please advise,
Brian
Edited 12/2/2008 1:00 am ET by bmyyou
Replies
Here is a schematic to help explain the problem
from what I can tell, my humble opinion is that you need to forget about the tenons and deal with the shoulders first. have you physically held the top and bottom rails together to see if the pieces are the same length? have you checked the shoulders with an accurate square, or against each other, first one way then rotate 180 degrees on either axis? most important do the shoulders fit the legs tight while the assembly is out of square (I doubt it), or are they tight on one end and not the other. If the shoulders are square and equal, but not mating with the legs without gaps, then, yes, the mortises and or tenons have been somehow miscut, or the shoulder to shoulder lengths are not equal, or the legs bowed. If it is the joinery (you can't get the piece all the way together), maybe the mortises need a little widenning from top to bottom? this wouldn't detract from the glued strength much. Any help?Brian
Edited 12/2/2008 2:21 am ET by BrianDerr
Brian,
Two of the four shoulders actually fit flush so they are pretty good; the other top two corners don't fit well. I'm sure it is the shoulders of the tenons (the tenon lengths don't matter as long as they don't touch the inside of the mortise). So how to fix the shoulders?
Square them up on the table saw. Attach a piece of plywood to your miter gauge as an auxiliary fence. Leave it a bit long and cut through it with the saw blade. This gives you the exact location of the cut.
Measure the length of the shortest shoulder-to-shoulder distance from the rails and transfer it to the auxiliary fence. Attach a piece of thin stock or plywood as a stop. It must be thin enough not to contact the tenon. This way the stop block registers against the shoulder, not the end of the tenons. Set the saw blade to the correct height and cut the shoulders on one end of each tenon. The shoulder-to-shoulder distances will now be identical. If any of the tenons are too long, trim them off.
Edited 12/2/2008 11:01 am ET by photonut
Brian:
I'm not sure I follow what your problem is exactly, but FWIW, the overall lenghts of these pieces, or the lengths of the tenons, mean exactly squat to how square the chair ends up. The critical measurements are the measurements between the shoulders of each piece and the squareness of the shoulders, tenons and the chair legs.
How did you cut the shoulders to begin with? You can either use a saw (hand, table or radial arm) to get these pieces equalized by trimming back the shoulder of the longer piece(s), or you can use a shoulder plane. If you're good with a chisel, you can even use that, but it's tough to keep the cut line straight and square with a chisel. (Hint: You need to first scribe a nice DEEP line with a marking knife and undercut just a bit with the chisel.)
I usually mark out matching rails at the same time, ganging them on the bench and making my cut marks with a try square. If you are making them with a power saw, you need to first make sure that each matching piece is exactly the same overall lenght and set up stops to cut the shoulders at the appropriate distance from the ends. And even then, I often mark the cut lines just to avoid any surprises from, say, a stop that moves a bit during use.
Mike Hennessy
Pittsburgh, PA
Of all the problems in chairs, and indeed in any M&T design, this is the easiest to diagnose and fix. Two suggestions:
1. Check for Square. Your shoulders are either square to the rails or not. Get out a square and check them. If square, then the two rear legs ought to be parallel unless the Shoulder lengths are different.
2. S-S Measurement. There is a measurement which I use in chairs and tables which as other posters have stated is super important--it is the Shoulder to Shoulder measurement. To heck with the tenon lengths--they are irrelevant. But the S-S measurment must be exact, right on the money, spot on. If not, no matter how square your tenons are, the legs will not be parallel.
I'd check these two items and get back to us.
Did you resolve this issue? How?
I'm still working on it; after reading the advice/feedback here, I realized that the shoulders and cheeks of the tenons are not flat/square. So I took a good combination square and scribed a line all the way around the end of the rail with an x-acto blade. I then trimmed just shy of the line with the table saw and cleaned up the faces with a chisel - this seemed to square up one end of each of the rails.
Now I will have to use the jig method suggested earlier and cut every shoulder-to-shoulder distance the same. Will tackle that tomorrow after work and let everyone know how this works. The tenons/ends that I cleaned up with the chisel this evening fit against the leg a lot better so I'm hopeful this will work.
On the S-S distance. I use a cheap mdf story stick to insure their precise match.Regards, Scooter "I may be drunk, but you're crazy, and I'll be sober tomorrow." WC Fields, "Its a Gift" 1934
do you cut to a line from the story stick on the table saw, or do you use a jig for that? I'm not sure if I could cut them to the line without some support.
Thanks
We are dealing with a dimension between two legs, either the two sides, e.g., between the two back legs or two front legs; or between the front and the back, e.g., between the front and the back legs.
Those legs are supposed to be "x" inches apart. When I build a chair, it matters not what "x" is supposed to be as long are we are fairly close. It could be x-1/16 or x.
What is important is that "x" remains constant. So, assuming the dimension is 19 inches between the legs, then I make a full scale drawing on quarter inch plywood showing those dimensions. I then cut a story stick to about 19 inches and compare it to the full scale drawing, and get it as close as I can.
I then lay out my rails to length factoring in the length of the tenons. Cut set up tenons so that the S-S measurement matches the story stick and full scale drawing. Adjust set up accordingly until they are spot on. This may entail keeping the tenon set up the same and simply reducing or expanding the length of the rail stock or visa versa.
I then assure that all the chair rails match the story stick by feel (thumb or forefinger) spot on. Of course, I also lay the rails out to the full scale plan and double check visually, but frankly my thumb and forefinger can do a better job of discerning length than my eyes can.
Regards, Scooter "I may be drunk, but you're crazy, and I'll be sober tomorrow." WC Fields, "Its a Gift" 1934
Stop blocks are a beautiful thing. If your table saw cuts true, you can be done with this issue pretty quickly. Attach a fence to your miter gauge, like I mentioned in my previous post about the thin stop block. Leave it long enough on the right side of the blade to attach a stop block. Cut through it, so you can see the exact cut line. Attach a stop block on the right side that registers against the end of the rail, not against the shoulder. The stop block should be set to control the length of the tenon. Don't forget to allow for the blade thickness in your measurements. Cut the shoulders on one end of each rail, re-set the stop block for each tenon length. Once you have one end squared up with the above method, use the thin stop block method against the shoulder described in my previous post. The shoulders on the tenons and the shoulder-to-shoulder distance will be perfect.
I'm really encouraged by your suggestion because I am ready to call "time of death" on getting these trued up again, however I'm not understanding the first part of your suggestion to work off of the tenon lengths. The tenon lengths for both the short and long tenons vary and are not exactly 1" and 2.5", respectively, so I don't see how to use the stop block on the right side of the fence to square up one side of the rails.
If I first run the fence through the saw to establish the cut line, what do I then line up on that cut line and how do I use the stop block?
Thanks a million - I really would like to recover these rails as some of the wood is quartersawn (more expensive cut).
Brian
What are you using to cut the tenons? It sounds like a table saw with a miter guage.Regards, Scooter "I may be drunk, but you're crazy, and I'll be sober tomorrow." WC Fields, "Its a Gift" 1934
Yes, a table saw with a fence attached to the miter gauge.
If using a table saw and stop blocks, this is how I would do it.
Cut some scrap of the same size, e.g., set up stock. I use poplar or glued up pieces of mdf. Figure out the approximate length of the rail including the tenons. Use a square to square up the miter guage to the saw blade. Using a pencil line, approximate the S-S lines. Compare your layout lines with your full size plans or a story stick to make sure you pretty close. If not, adjust your layout lines.
If you have a wide table saw, move the fence all the way to the side and clamp a small piece of wood to the fence on the operator side of the blade. Adjust the fence so that the set up rail, when place on the stop block, is cut at the layout line you marked. Mark the location of the fence using a strips of tape and pencil lines. Use your miter guage to cut that layout line which is your tenon shoulder. Adjust the depth of the saw blade and cut the cheeks of the tenons.
Remove the rest of the wood on the shoulders with a series of cuts on your table saw or use a dado blade. Check the tenon shoulders for square, and adjust the miter guage if necessary.
Adjust the fence for the other tenon layout line and cut as above.
Now, make 2-3 practice pieces. Your challenge is to produce a square tenon (which ought to be pretty close if you followed the instructions) and a consistent S-S measurement (which with a table saw set up is a bit more difficult). A sharp pencil or marking knife will make thinner lines and more accurate layouts. A hand chisel or a shoulder plane can adjust the tenon shoulders and cheeks to be consistent with your full size plans and/or story stick.
Once you can make 2-3 pairs of good rails with consistent results, then it is time to move the quarter sawn oak.
I have to tell you, I'm an idiot, and I practice with mdf set ups, and popular before moving to the real deal. If you own a planer it is no big deal to mill this stuff up; If not, have the hardwood supplier mill you up idential thicknesses of popular for set ups and practice. I do it all the time.
Other ways with a table saw might include a table saw tenoning jig which will get the tenons perfect to the layout lines, and instead of adjusting the layout lines, one leaves the tenon depth as is, and simply shortens the piece until the S-S lines matches the full size plans and/or story stick. I have also made tenons on radial arm saws (one of my favorite ways to do it) and currently use a tenon jig for a router. All the above involve keeping the tenon sizes the same and simply shorting the rail size to get it to the right S-S measurement.
Regards, Scooter "I may be drunk, but you're crazy, and I'll be sober tomorrow." WC Fields, "Its a Gift" 1934
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