Routing mortices for loose tenons

[DigitalM]

I've been experimenting with loose tenons, routing the mortices on the router table with a 10mm twin fluted cutter on a 1/2" shank.

If anyone does this sort of thing regularly, what's the max depth you'd consider cutting in a single pass? Obviously, I expect this changes with the type of wood being worked, but if you can give basic rules of thumb you use yourself that would be useful.

I've also seen references online to up-cutting spiral bits. I can use ER20 collets so this is something I may be able to use relatively easily. It sounds like the advantage with these is that they clear out the waste better - but how is the finish and the max-depth-per-pass compared to regular router flute bits.

 

[morturn]

I have done lose tenons a couple of times. I am not a fan of them, only because I like doing m&t joints.

I go with a depth of cut no greater than the diameter of the cutter.

 

[ColeyS1]

The rule always use to be half the diameter of the cutter. You'll soon be aware when you're routing too much. If you've got a nice sharp cutter you'll be able to take more each pass. I think a safe suggestion would be the diameter of the cutter is probably the maximum you should try.
Coley

Sent from my SM-G900F using Tapatalk

 

[Phil Pascoe]

I always find it much better (assuming your cutter has a bottom cut - most now seem to) to plunge a series of holes to the full depth then clean up the sides - it puts less strain on the cutter. It works perfectly well on lock mortices.

 

[Steve Maskery]

Whilst using a router to cut loose tenons is perfectly reasonable, and all good advice above, using a Router Table to do so seems to me to be less sensible.
With a vertical jig in the vice I can set the depth and plunge to it by hand, in a series of shallow cuts, and I can feel if it starts to complain. But in a RT, to get to a depth of, say 30mm, I would have to take 6 separate cuts, each time stopping the router, adjusting the height and starting up again. Perfectly doable, of course, but it would take forever.

 

[Mr T]

Whilst using a router to cut loose tenons is perfectly reasonable, and all good advice above, using a Router Table to do so seems to me to be less sensible.
With a vertical jig in the vice I can set the depth and plunge to it by hand, in a series of shallow cuts, and I can feel if it starts to complain. But in a RT, to get to a depth of, say 30mm, I would have to take 6 separate cuts, each time stopping the router, adjusting the height and starting up again. Perfectly doable, of course, but it would take forever.

I would agree with Steve. I never feel quite right dropping work onto the cutter on a table, even though I always use stops, it just seems inappropriate, plus there can be guarding problems. Better to use a bench muonted jig and hand held router. I also agree with Phil P., better to take a series of plunging cuts first then remove the remainig fllutes with a routing cut. The first couple of plunge cuts should not go full depth because of problems with waste removal, return to them to go full depth before doing the routing cuts.

Chris

 

[Steve Maskery]

Regarding the plunging action, I plunge whilst cutting the length of the mortice, that way there is better bottom cut. Still shallow cuts, of course, but it gives better chip clearance. It's a sort of zig-zag motion.

 

[custard]

If anyone does this sort of thing regularly, what's the max depth you'd consider cutting in a single pass? Obviously, I expect this changes with the type of wood being worked, but if you can give basic rules of thumb you use yourself that would be useful.

The normal rule of thumb is you can't route in a single pass deeper than the diameter of the router bit, so with a 10mm diameter bit you could plunge and route to a 10mm depth.

Personally I've found that with the latest generation of solid carbide, spiral, up-cut bits you can go further than this, I regularly plunge and pass to 1.5x the diameter of the bit without problems in hardwoods. Another option is "pre-drilling", use the up-cut router bit to plunge a series of overlapping holes the length of the mortice and then clear out the remaining waste with a single, full depth cut. This works okay for the 25mm deep x 8mm wide, or 30mm deep x 10 or 12mm wide loose tenon mortices that I normally cut this way.

I agree with Steve that a router table isn't the best method for loose tenons. This joint is very commonly used in jointed chairs where you're trying to avoid weak grain and awkward geometry on angled tenons/angled mortices, in that application you pretty much always make up a simple jig and just use the router hand held.

Good luck!

 

[Beau]

I don't do it often but when I do I use an up-cut spiral like a drill. I work along the length of the mortice plunging overlapping holes and then do a couple of passes to clear whats left. Very clean and efficient and is kind to cutter instead of just blunting 10-12mm at the end. Even do this for door locks with a 1/2 cutter plunging 65mm!

 

[morturn]

You may find this video useful

https://youtu.be/zORuOdjasMo

 

[Cordy]

My limited experience....
I've used in table; plunging down with stops, guards and more protectors -- always left me feeling nervous

Using a jig and free-hand mortising for lose tenons is OK but slow

This half inch bit is good btw -- LINK

Enter the Domino 500

Sheer bliss, gets the job done quickly and efficiently
Mostly use 8 mm but have the full range of bits and dowels

Regarding how deep, the feel of the router should be a good guide; you just need to experiment on scrap timber

 

[Phil Pascoe]

If you are not using some form of jig, it pays to either own or make up some sort of second fence so the router doesn't kick sideways.

 

[DigitalM]

Whilst using a router to cut loose tenons is perfectly reasonable, and all good advice above, using a Router Table to do so seems to me to be less sensible.
With a vertical jig in the vice I can set the depth and plunge to it by hand, in a series of shallow cuts, and I can feel if it starts to complain. But in a RT, to get to a depth of, say 30mm, I would have to take 6 separate cuts, each time stopping the router, adjusting the height and starting up again. Perfectly doable, of course, but it would take forever.

Hit the nail on the head with regard to why I asked the question. However, I'm getting good results, but on hearing all this I'm thinking that I'll finish this round of work the way I've started then explore other options.

 

[Steve Maskery]

This half inch bit is good btw -- LINK

I used to use such a bit on the advice of James Krenov. It was OK but quite slow. The clearance angles are designed for metal, not wood, so the cutting and chip clearance is not as good as one might expect, and it is easy to blue the cutter.

A proper wood spiral bit would be best, but they are expensive c.f. a standard cutter of the same size. A good compromise is the Clico horizontal mortising bit, one "normal" edge and one serrated edge. The main problem is that they are intended for use in a horizontal mortiser running at, say, 5000 rpm, not a router at 8000 minimum. Because of the two different edges they are not balanced like a proper router cutter is and so they are prone to vibration. The 1/4" cutters, in particular, are easy to break, though I never did break the 3/8" or 1/2" ones. I don't have them any more or else I would post a pic.

 

[woodbrains]

This half inch bit is good btw -- LINK

I used to use such a bit on the advice of James Krenov. It was OK but quite slow. The clearance angles are designed for metal, not wood, so the cutting and chip clearance is not as good as one might expect, and it is easy to blue the cutter.

A proper wood spiral bit would be best, but they are expensive c.f. a standard cutter of the same size. A good compromise is the Clico horizontal mortising bit, one "normal" edge and one serrated edge. The main problem is that they are intended for use in a horizontal mortiser running at, say, 5000 rpm, not a router at 8000 minimum. Because of the two different edges they are not balanced like a proper router cutter is and so they are prone to vibration. The 1/4" cutters, in particular, are easy to break, though I never did break the 3/8" or 1/2" ones. I don't have them any more or else I would post a pic.

Hello,

Krenov didn't use them in a router!

I use them as he did in a horizontal drill with a table for support. In my case, I use my swivel head woodturning lathe and a collet chuck to hold the end mills. Done this way, at much lower speeds than a router, the bits do cut very well, clean walls and very controllable and safe. Not quite as fast as slot mortice bits, but more accurate slots and as I said, hand fed and controllable. No danger of blueing the bits, of for that matter, wearing them out!

Mike.

 

[Steve Maskery]

Ah, thank you, I didn't realise that! Oops!

 

[Mr T]

This is all getting bit complicated an ordinary straight flute cutter will give good enough results, preferably on a half inch shank.

Chris