Making A Stub Haunched Tenon & Mortice???

[pollys13]

Making A Stub Haunched Tenon & Mortice???

I want to put a mortice in 40mm thick stock. Using the rule of 3rds the tenon should be close to 14mm wide.
I propose making the mortice using my floor standing pillar drill, the timber used will be the hardwood Utile.
Using a 14mm wide brad point drill bit to drill a starter hole to the depth of the mortice. Or perhaps a Forstner bit?
Then use a 14mm two flute straight cutting router in my 1/2" router to make successive
passes to get down to the depth of the mortice. Would I be better using a different cutter, perhaps an upward spiral cutting bit?
Then use a hand morticing chisel to square out the ends of the mortice. A 14mm mortice chisel is available.
Where I've mentioned 14mm is it alright to have it all 14mm, all fit together, machine ok?
Also when I come to make the stub haunched tenon, or stub tenon. As the mortice is 14mm wide how wide should I make the tenon to allow the glue to get in properly to make a secure glue join, 12mm, 13mm?
Also how far from the bottom of the mortice?
I'll be using a Grizzly tenoning jig on my cabinet saw to make the tenons. Do I need to make a haunched mortice to accept the haunched tenon, If so how could I go about doing that, several ways to do it?
Thanks.

 

[Jacob]

So called "rule of thirds" is only a rough guide so in 40mm stuff (square?) you could do up to say 20 wide but down to 12 thick (i.e. width of hole) for which you would need a 12mm mortice chisel if possible. Or if 1/2" available use that and do a 1/2" tenon. For no good reason at all I tend do haunches at 1/2" too, but perhaps a bit less in 40mm stock say 8mm? The depth needs to enough to allow for a good fit but doesn't need to be any more or it weakens the stile. To allow excess glue to escape from a stopped mortice a fine drill hole in the bottom (1mm) will fill with glue and be invisible

 

[custard]

Have you cut mortice and tenon joints before? If not practise on some scrap first.

There's no need to use a pillar drill first if you plan on cutting the mortice with a router, just go straight to the router, a half inch router bit is cheap and easy to find, it's close enough so i'd probably use that. The ideal bit is a solid carbide spiral upcut. If you plan on cutting loads of mortices it might be worth getting, but they're a bit pricey where as a two flute 1/2" bit is the staple of the kitchen fitting trade and is therefore as cheap as chips...just make sure you get a bottom cutting version.

The trickiest part of routing mortices is to prevent the router tipping, if you can gang up the components next to each to give a wider more stable base to run the router on, do a practise pass first with the power off to check nothing will foul the router's smooth movement and that you're not tipping...even a tiny bit!.

Plunge a series of overlapping holes to full depth first then go back and clear out the waste with successive passes, each about 6 or 8mm deeper than the last. I know that's the long way around but if you haven't cut many mortices then it's the surest way.

The tenon needs to be a friction fit. In reality that means about 0.1mm less than the mortice width...yes, tolerances are very tight! You might be better cutting the tenon slightly over thickness then trimming it back with a shoulder plane or even a paring chisel. If you go too far you can glue a bit of veneer to the cheeks of the tenon to rebuild the width, not great but way better than hoping PVA glue will hold it! Alternatively you can use a gap filling glue like epoxy (big gaps) or Cascamite (little gaps). Polyurethane is not a gap filling glue in spite of many people believing it is.

Good luck!

 

[woodbrains]

Hello,

Have you considered making twin mortice and tenon joints? Something like 10mm tenons side by side, a 8mm space between and 6mm shoulders each side. Regular sizes of mortice chisel are used, it gives a greater glue area and does not weaken the timber as much as a whacking great single mortice. It is what I'd do in similar situations.

Mike.

 

[PAC1]

I worry when I read that you have a drill press, a router, a cabinet saw, a tennon jig and then you ask about making a mortice 14mm wide indicating that you have 14mm brad and Forstner bit, 14mm router bit and could get a 14mm mortice chisel. You then ask if the tennon should be 12 or 13mm wide. I can honestly say that in 36 years I have never felt the urge to buy anything 14mm it is such an unusual size. As Jacob said we make the joint as near as is sensible to suit the size of chise (or router bit)l we own so 12mm, 16mm, 18mm or 20mm are all reasonable. Further unless you are making a lot of mortice and tennons at this size it is a very expensive and laborious way of working. If it is less than 4 you can cut them by hand in less than the time it takes to set up all those machines
Can I suggest, if it is not too late, that you get a 12mm or half inch mortice chisel, mallet and saw and make a few mortices and tennons by hand. you will then learn what makes a good or bad mortice and tennon and that you are looking for a piston fit. you will see that the 3rd rule is more guidance than actual rule.

 

[andersonec]

A Mortice chisel is just that, a 'Mortice chisel' and it is for chopping out a moritce without the use of any other tools, drills or routers. If you are going to use these other machines then you need to clean up the hole with an ordinary chisel. The marking out and accurate cutting to the centre of those lines will be the ruling factor as to whether you mortice and tenon will fit.

Andy

 

[Paddy Roxburgh]

for most applications a 1/2" tenon is wide enough (12 or 13mm if you have metric tooling). https://www.youtube.com/watch?v=-ygBmNrQkN4 is not a bad video for using a router to cut mortise. He doesn't pre drill with the router as custard recommended, either way is fine. Successive passes getting deeper each time is essential.
If you want a more pleasant experience use a chisel, mortice chisel is nice but bevel edged chisel is fine https://www.youtube.com/watch?v=aBodzmUGtdw might be helpful
Ideally the tenon is the exact size of the mortice, don't worry about the glue, just make it fit and put glue on both surfaces.
If you cut the tenon with a table saw jig and the shoulders on the tablesaw or bandsaw I would still recommend cutting the haunch by hand with a tenon saw, any machine process for this task will take more time for no advantage

Hey Jacob, what#s the 1mm hole about, that's a new one on me, I take it you don't actually drill all the way through? I just make the tenons slightly shorter (maybe 2 or 3mm) than the depth of the mortice.
Paddy

 

[Jacob]

......
Hey Jacob, what#s the 1mm hole about, that's a new one on me, I take it you don't actually drill all the way through? I just make the tenons slightly shorter (maybe 2 or 3mm) than the depth of the mortice.
Paddy

I had some drawer knobs spigots popping out just after I glued them in, or not going all the way home, due to pressure in the stopped hole - hence a weep hole. The better the fit the more you need one! You can even get thin stuff splitting under hydraulic pressure but the main thing is pressure relief for a close fit.

 

[custard]

He doesn't pre drill with the router as custard recommended, either way is fine. Successive passes getting deeper each time is essential.

There's a reason I suggested that. I don't know how much experience the OP has, but I'm assuming from the question not much. After you've used a router for a while you instinctively learn to counter the tendency for the cutter to spiral away from the line, with experience you make sure the fence is tight to the workpiece both fore and aft, applying compensating twist where necessary. But first plunging a series of full depth overlapping holes with the router is a way of ensuring a newcomer can achieve a straighter cut. Actually I've seen many more experienced workers produce rails that are slightly twisted relative to the stiles, the most likely explanation is that they're also cutting mortices that aren't dead parallel to the face of the stile, it's a particularly easy mistake to make with router cut mortices because the temptation is to cut from both left to right and also right to left, so the left hand end of the mortice gets slightly over cut towards the fence.

 

[Paddy Roxburgh]

......
Hey Jacob, what#s the 1mm hole about, that's a new one on me, I take it you don't actually drill all the way through? I just make the tenons slightly shorter (maybe 2 or 3mm) than the depth of the mortice.
Paddy

I had some drawer knobs spigots popping out just after I glued them in, or not going all the way home, due to pressure in the stopped hole - hence a weep hole. The better the fit the more you need one! You can even get thin stuff splitting under hydraulic pressure but the main thing is pressure relief for a close fit.

Probably I've never had a good enough fit to encounter the problem, will bear this technique in mind if I do encounter such an issue. Is this something you do as a matter of course or just when you encounter issues?
I'll never be a writer, I just said "encounter" three times in two sentences (and issue twice). Damn, now it's 4 and 3, I'm gonna finish this glass of wine and go to bed

There's a reason I suggested that. I don't know how much experience the OP has, but I'm assuming from the question not much. After you've used a router for a while you instinctively learn to counter the tendency for the cutter to spiral away from the line, with experience you make sure the fence is tight to the workpiece both fore and aft, applying compensating twist where necessary. But first plunging a series of full depth overlapping holes with the router is a way of ensuring a newcomer can achieve a straighter cut. Actually I've seen many more experienced workers produce rails that are slightly twisted relative to the stiles, the most likely explanation is that they're also cutting mortices that aren't dead parallel to the face of the stile, it's a particularly easy mistake to make with router cut mortices because the temptation is to cut from both left to right and also right to left, so the left hand end of the mortice gets slightly over cut towards the fence.

As always Custard your advice is spot on. When I used to use a router more I would cut mortices on the woodrat jig (now mostly gathers dust and wastes wall space), I would drill holes to full depth and then clear the waste to the previous hole, I got this method from the woodrat manual, I believe the thinking was that it was the last likely way to make the work jar in the clamps, essentially the same issue as using the router freehand with a fence and the router jarring (or wandering a little)

Paddy

 

[PAC1]

......
Hey Jacob, what#s the 1mm hole about, that's a new one on me, I take it you don't actually drill all the way through? I just make the tenons slightly shorter (maybe 2 or 3mm) than the depth of the mortice.
Paddy

I had some drawer knobs spigots popping out just after I glued them in, or not going all the way home, due to pressure in the stopped hole - hence a weep hole. The better the fit the more you need one! You can even get thin stuff splitting under hydraulic pressure but the main thing is pressure relief for a close fit.

Jacob's method is fine when the hole is in some out of the way location but where any blemish will be seen you can cut a little groove in the length of the tennon so that the air and glue can escape up to the point the shoulder squeezes up

 

[pollys13]

Thanks everyone for their views.

 

[woodbrains]

......
Hey Jacob, what#s the 1mm hole about, that's a new one on me, I take it you don't actually drill all the way through? I just make the tenons slightly shorter (maybe 2 or 3mm) than the depth of the mortice.
Paddy

I had some drawer knobs spigots popping out just after I glued them in, or not going all the way home, due to pressure in the stopped hole - hence a weep hole. The better the fit the more you need one! You can even get thin stuff splitting under hydraulic pressure but the main thing is pressure relief for a close fit.

Jacob's method is fine when the hole is in some out of the way location but where any blemish will be seen you can cut a little groove in the length of the tennon so that the air and glue can escape up to the point the shoulder squeezes up

Hello,

Neither holes nor grooves are ever necessary, since tenons only fit closely to the mortices at the cheeks. There is (should be) space at the ends where air can escape, so the hydraulic effect is not present as it is with dowel joints. A little extra depth on the mortice allows space for a little excess glue. Brushing glue into the mortice and on the tenon, just enough to wet both surfaces means that the joint will not be glue starved, nor have excess glue to need to be vented.

Mike.

 

[Jacob]

....
Neither holes nor grooves are ever necessary, since tenons only fit closely to the mortices at the cheeks.

Unless it's a really good fit

There is (should be) space at the ends where air can escape,

sloppy!

so the hydraulic effect is not present as it is with dowel joints. A little extra depth on the mortice allows space for a little excess glue. Brushing glue into the mortice and on the tenon, just enough to wet both surfaces means that the joint will not be glue starved, nor have excess glue to need to be vented.

Mike.

I prefer a good fit and too much glue rather than sloppy and too little. You can very easily get the piston effect. A 1mm hole filled with glue will be invisible on most wood surfaces.

 

[PAC1]

I use titebond and probably prefer more rather than less glue. It is quicker and less chance of a joint failure. Given this is quite a thick glue the hydraulic effect is a very real issue