Thread: Mortising Jig

Harry,

That is a very interesting version of my jig, but most of us don't have access to CRC. I have been wondering about how to make the jig in aluminium, in order to enable the horizontal platform to be made thinner (and thus maximize the depth of the mortice that can be routed). But I wasn't able to come up with a way of making it that the ordinary hobbyist, without access to specialised equipment, could use. Maybe, if you could come up with an aluminium version it might be a commercial proposition to rival the Trend and Leigh jigs.

If you made it in metal, maybe you could build in a vernier scale that would provide high accuracy without the need to have a gauge.

Rocker

An all aluminium jig would be good as it would be very light, too make it would be a different story, idealy I would redesign it so the whole top plate would traverse on the upright support with a fixed fence for the router base to guide against, this way the top plate could be made quite thin say 2mm with braces along the outer edges. The top plate wouldnt need all the excess behind the fence guide either...
Also a extra adjustable fence along the front to gain the best control while cutting mortices would be good to limit any miss cuts.
Im finding the limitations allready like you say the plunge depth is a problem with a 5/16 Sp'upCut bit 40mm seems to be the max cutting a mortice, Im loosing 16mm to start with!
3mm Mild steel would be the go to make a prototype or 3.
Hmmm its got me thinkin about tinkerin... but alas must make some furniture 1st keep the SWMBO happy, she had her 1st neice born 18min's after Xmas so I'm making a nice blanket-X-toy-X-glory box for the baby, the name they gave her is "Lauren Kate" might even carve her name in the top!(sure beats flowers)

Hi Rocker,

is the hotmail a/c you mention earlier in this thread still active?
I am interested in the plans for the jig as I wish to involve myself more with mortice and loose tenon techniques.
Regards
Les

Les,

Yes; e-mail me, and i will send you the plans.

Rocker

Rocker, how much free play should I allow when cutting M&T's, as tonight I glued up some M&T's and ended up spilting the wood through "hydraulicing"(flogging a drag racers term...). The joints slipped together well without any fuss with outglue, when I pull them apart I get a popping sound(like when pulling your finger out of a glass bottle).
Those joints had a clearance of .02mm, obouviously thats not enough space to allow glue(pva)to move thoughout the joint.
So whats the go, like .5mm overall(.25 each side)?

Ps, I got too many zero's in my post above I said .002 when I ment .02, Hmmm working in thou's of mm on woodwork!

Harry,

I aim for clearance of about 0.03 mm on either cheek of the tenon - i.e., the tenon about 0.06 mm thinner than its mortice. I avoid the hydraulic problem by not rounding the ends of the tenon to fit the rounded ends of the mortice exactly, but slicing facets off the ends so that there is room for the glue to escape, as in the diagram below.

Would you also leave the tenon a few mm shorter than the depth of the mortice so that the tenon does not bottom out and leaving the excess glue somewhere to go?

SilentC,

Yes, that too; but space at the bottom of the mortice will not solve the problem, unless there is some channel by which the air trapped in the mortice can escape, as you push the glue-covered tenon, which is acting like a piston in a cylinder, into its mortice.

Rocker

Ah so leave some sort of "relief" for the glue to go.
Thanks Rocker

Received the plans Rocker thanks a lot. I might have a go at the Lite version when I get some time. Milling the spline might be a bit of a hurdle though.

In other news, how do you do the mortices in the curved pieces of your chairs?

Adam,

If you don't have a table saw to cut the spline, you could just rout a 3 mm deep, 6 mm wide, groove in the underside of the horizontal platform, and rout a rabbet on the top edge of the vertical support, so that there is a 6 mm thick 3mm long tongue left to fit into the groove.

Rocker

Adam,

I omitted to answer your second question, on how to cut mortices on the curved rails of my chair. There are two options:

Option 1. You can cut and fair the concave face on the front of the rails, and then rout the mortices by clamping the rail in a vice with a curved caul, and using a curved fence attached to the router's edge-guide. This method, of course, produces slightly curved mortices, but the curvature on a 30 mm long mortice is not noticeable.

Option 2. You can cut and fair both the back and front curved faces on the rail and then clamp the curved rail onto my morticing jig, so that the mark in the centre of each mortice in turn registers with the centre-line of the jig. This second option is easier.

Rocker

I have finally managed to draw the jig in 3D in TurboCAD. I attach four different views.

Rocker

Great work Rocker. What do you think of TurboCad? Mrs. Grunt is a student and I am thinking of getting a student copy of it.