Dear Fellow woodworkers
I am building a Morris chair in white oak, something I have never done before. The design I am following calls for through mortises in the arm (two per arm) for the front and rear legs, as well as through mortises in the legs (front and rear) for the rails. The mortises in the arms are 17/8″ square, and the arms are 11/8″ thick. The mortises in the legs (3/4″x11/2″) are even more challenging as the legs are 21/4″ thick. I have used a 17/8″ sawtooth bit to remove the bulk of the mortise in the arms and am planning to complete them with a mortise chisel. I plan to use a square block to guide the chisel. My question simply is this: does anyone out there have any tips or tricks for getting clean straight walls on the mortise in this hard and dense material?
Zav
Replies
Morris chairs were designed for machinery- I can't stand the style personally. So the original chairs would have been cut mass production style with some god forsaken finger eating machine. Disgusting- Am I being too dramatic?
The good news is you can skip all that. All you need is a good front and back face. What's in between matters less. So I say skip your block (that doesn't anyway work BTW*), and just scribe both sides with your mortising gauge (you do have a mortising gauge don't you?) and cut in from both sides.
If the mortises don't meet perfectly in the middle, DON'T OPEN UP THE MORTISE. Just trim the one wall that's sticking into the cavity, and leave the other undercut. This is how its been done for 250 years and it will work for you. Just be sure to be careful when you insert the tenon. Leave it long and chamfer the end so it doesn't splinter the far side. Then trim it flush after its glued in place.
No worries, tho. If you screw it up and its a little loose, hide glue (be sure to hide glue these joints) hide glue in a shim or some tiny wedges.
Adam
* When you chop with a chisel (whose cross section is a wedge) the wedge shape wants equal pressure on both sides. So if you hold your chisel straight up and drive it straight down, it will undercut. So you can't use your block for the end cuts or for paring cuts the walls.
Just in case you don't know (you may know all this already) the blocks were/are used to align the SIDE of the chisel. You probably won't be able to use it this way, since you already excavated the area with some unspeakable electric appliance. So you are probably out of the mortise chisel usage arena. Believe it or not, your task may have been easier if you had just cut the whole joint by hand, or used a hollow chisel mortiser for the whole job. Its the mixture that forces you into the use of the paring chisel and makes things actually more difficult.
So I guess I want you to know this may be tricky for you. It may be tricky to get the joint you are expecting because the original joints weren't cut the way you are doing it. That's not to say its impossible, however. So my advice is to scribe both sides and then carefully pare to those scribe lines, knowing that a block won't help you.
Good luck brother,
Adam
Edited 2/17/2006 9:09 am ET by AdamCherubini
Am I being too dramatic?
NOT if you are Female AND a Brunnete.. I married one and they get a 'BIT' Dramatic?
Yes, but you are humorous and knowledgable. If you cut through the ****, the advice on those through mortises is basically what I did on my Morris chair. Actually, cutting the angled tenon cheeks correctly was much harder than making nice through mortises. Don't force the arm down over the tenon in getting a good fit. I cracked an arm doing it. Not my arm...the chair arm!
Serious answer.. REALLY hard fer' me! I just.. "TAKE MY TIME".. I do not have much left I'm so old BUT I really do take my time..YES.. I DO use a SQUARE wooden block as a guide for my SHARP chisel.. I 'sneek' up on it and get a prefect fit.. Whatever that is?Actually, cutting the angled tenon cheeks correctly was much harder than making nice through mortises. What you posted...
Actually, cutting the angled tenon cheeks correctly was much harder than making nice through mortises..IT SHOULD BE! If ya' did it right!Woodworking is like your FIRST KISS! Hard to get BUT ya' ALWAYS REMEMBER IT!EDIT! I ments' to say..
Woodworking is like your FIRST KISS! Hard to get Right BUT ya' ALWAYS REMEMBER IT! If ya smooth out the rough edges till she is SMOOTH!Edited 2/23/2006 8:51 pm by WillGeorge
Edited 2/23/2006 8:55 pm by WillGeorge
Will,
Woodworking; like the first kiss... better if you don't bump your nose?
HaHAHHH
Ray Pine
When you chop with a chisel ..I CHOP back a 'BIT' from the line.. I chop out what is needed.. I re-sharpen then 'Pare?' off the left-overs..
Adam- Can you explain why you said to be sure to use hide glue on the through-mortise joints? I know you probably use hide glue only, and from horses with very old blood lines, but what is it about this application that recommends its use to us mortals?
PS. I'm trying to picture your hand-split sawhorses in my shop..........
Edited 2/24/2006 11:59 am ET by Vicejaws
Its my belief that hide glue has gap filling properties. I've come to this based on personal experience, historical samples, and discussion with Eugene Thordahl of Bjorn Industries. That said, I could be wrong.
We know that yellow glue requires high bondline pressure to achieve bond strength (150-250psi). M&T joints are unclampable. So if you can't produce the pressure required by a piston like fit, its unclear what is holding the joint together and how much glue strength exists. So it appears to me a slightly gappy joint, glued with hide glue may well be the stronger joint. Though the tenons are said to fit tightly, 18th c philadelphia chairs often exhibit under cut mortises. Hide glue tends to extrude out of tight joints. So the undercut may have served double duty: allowing a place for a gap filling glue while allowing for inexact chopping!
Of course the other reason is that hide glue is easily, non-mechanically repairable and reversible. So its an especially good candidate for an heirloom Morris chair.
Adam
When you say that M&T joints are unclampable, are you referring to attaching the shoulder to the face or just through tenons? Why can't it be clamped? A caul with a hole for the tenon to project into would make it work by providing a clamping surface. What about using straps to pull the joint(s) together? Just wondering, do you hate all power tools or just the electric ones? The Shakers came up with the idea of a powered circular saw in about 1810 and other wind and water powered machines were invented in the mid-late 1700's. Set up correctly, a machine can produce a more accurate and repeatable joint than hands, often in less time, depending on the joint. Even 200+ years ago, money was the motivating factor in power tools for dimensioning lumber and moulding production but fine pieces were made in those times. Then again, when isn't $ a big factor?OTOH, if your point is that being able to achieve extraordinary accuracy, aesthetics and durability by hand are some of the ultimate goals in woodworking, I agree. Another goal that should be at the top of the list is constant improvement, IMO. I would have a hard time believing that working by hand is the only way to produce great furniture or other items made of wood."I cut this piece four times and it's still too short."
Edited 2/25/2006 11:24 am by highfigh
Regarding "unclampable" M&T joints:You get no strength from an end grain to long grain glue joint. So the glue at the tenon shoulder is irrelevant. So how do you hold the tenon in the mortise? Peg it? Friction? Hopefully you have some glue bonding the long grain of the tenon to the long grain inside the mortise. How do you clamp that joint? That's the trick. Got it?
Adam,
Ive noticed a couple of comments in a few threads on this recently and am intrigued - I certainly dont recall issues such as the separating mesh for ensuring a correct gle line or the optimal clamping pressure for different glues being mentioned in the "what glue to use" article in a FWW from last year.
I have recently been using the sort of poly glue that foams out a bit during curing. I like the post-glue clean up but also the apparently longer open time for when I am mucking about during glue up (you know, forgot to tape the clamps, not holding the toung in the right directon etc). Also, this glue is being recommended locally as suitable for the red gum I have used on the last couple of tasks as it is suoesed to deal well with any moisture variation in the timber (not sure why this would be any more of a problem in eucalypts)
So, is there a similar clamping problem with the polyurethane, and would you still go fo the hide glue - I have several ostensibly well bred horses that based on recent exploits with my childern might be good candidates for restocking the glue pot.
david
If you want to do this as you describe by taking out the waste with a drill, here are my thoughts/suggestions:
1) If you don't have a drill press to make sure the drill is perfectly straight and aligned, don't use a bit that is the exact width of the final mortise. Go a bit under and clean up the sides. Drill 1/2 way from each side.
2) I personally hate using mortise chisels after drilling. I find they bind too much, are hard to keep straight, and it's hard to get clean edges. Anyway, mortise chisels are designed to cut mortises the exact width of the chisel and I doubt you have a 1-7/8" mortise chisel, unless you are a timber framer! ;- ) For mortises this size, (if I wuz pre-drilling 'em), I'd carefully mark out the mortise on each side of the work; drill out the center waste, 1/2 from each side; cut from the center hole to each corner with a coping saw or fine keyhole saw; then chisel to the line on each edge of the mortise, 1/2 depth from each side. I'd try to leave about 1/16" waste to chop out after drilling, which means you would use a 1-3/4" drill, max, for 1-7/8" mortises.
Don't worry about white oak being hard. It's not really that hard compared to other hardwoods and works pretty nicely with hand tools.
Mike Hennessy
Pittsburgh, PA
Here's a thought that is based on a lot less experience than those who already posted.
If you've removed most of the waste by drilling and are paring to shape your mortise, you can keep your chisel aligned properly by looking at the surface as you pare. The flat you cut will have a cylindrical groove down the middle that gets narrower as the wall of the mortise moves out toward the limit of your bore. If the sides of the groove are straight and parallel, your mortise is aligning with the drilled hole. You can adjust your paring to make them parallel, and then the question is simply when to stop.
My understanding was that much of the reason for drilling first is so that you don't need a mortise chisel.
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