Thread: Mortising Jig

Rocker,

Looks the bee's knees. Any chance of posting some details, or do I need to hunt down the mag?

If you want a copy of the article. e-mail me at [email protected]

I forgot to mention that it is easy enough to use the main features of this jig, i.e. the parallel guide bars, the micro-adjustment by means of a threaded rod, and the gauge, to make a precision router-table fence. In fact I got the idea for this jig from Pat Warner's description in Fine Woodworking of a router table fence a few years ago.

Hi Rocker,
Have just been reading your impressive article and have a couple of questions.

For the fence block (part E), you say to tap the 6mm hole. Are you using a normal (metalworking) tap to cut the thread directly in the jarrah?
Without a tap, could you instead just epoxy a suitable nut to the block? Or is there a reason to have such a long thread?

You use brass runners for the fence, but hardwood runners for the stop blocks. Any reason you couldn't use hardwood runners instead of brass?

Note: these are not criticisms of your great design. I'm just wondering if I need to use the exact same hardware.

John,
I used hardwood guide bars for the stop blocks because a certain amount of play in the stop-block grooves does not matter. On the other hand, it is vital that the double guide bars for the fence are precisely parallel and that there is no play between the grooves in the fence and the guide bars. Wooden guide bars would be bound to bind, unless the grooves in the fence had a lot of play, owing to changes in atmospheric humidity. Metal guide bars are essential; but you could use aluminium bars, and they could be 1/4" thick to match 1/4" grooves routed in the fence and horizontal platform, I chose the 1/8" brass bars because they are easily available from Bunnings and I had a 1/8" router bit. The point is you need to match the thickness of the bar stock to an identical-diameter router bit used to rout the grooves.

Yes, I used an ordinary metal tap to tap the thread in the fence block; it is easy to tap the thread, especially if you chuck the tap in a drill press to start it off, turning the chuck BY HAND - NOT using the drill press motor. You probably could epoxy a nut to the block, as you suggest, but I thought that the glue bond might loosen after a time. I think it is anyway just as easy to tap the hole, as I suggest. I find it works very effectively, with very little backlash. I made the tapped hole relatively long in order to minimize wear and my jig still has virtually no backlash after three years' use.

A way to strengthen the thread would be to tap the jarrah as u described, then remove the tap, blow out any dust and run some thin cyanoacrylate (super glue ) into the thread. Once that has set, screw the tap in to clean up the original thread.

That will make the thread as solid as you can wish for.

Cya

Joe


Have fun............................keep turnin

I have recently made a new version of this jig using polythene ripped from a kitchen cutting board as the material for both the fence guide bars and the stop block runners. I cut the polythene a shade over 3/8" wide to fit into 3/8" routed dadoes, and fine-tuned the thickness of the polythene by laying it on a flat surface and planing off thin slivers with a jack plane, checking the width frequently with an electronic caliper, until the polythene strips could just be pushed into the dadoes in the MDF. In order to enable the wooden fence to run on the guide bars without excessive resistance, I used a very sharp chisel to pare the sides of the dadoes in the bottom of the fence until they were just wide enough to fit snugly onto the polythene bars.

The method of routing the matching pairs of dadoes is shown in a photo that I posted yesterday in the routing forum on the thread related to the ideal router table.

And what was the conclusion from your mod?

Is there much difference between the brass and the polythene?

Is the polythene very much smoother? Is is more stable/less prone to binding? Is it worth doing it this way, given the hassle of cutting it to size? You would never use brass again?

John,
I concluded that the polythene guide bars work just as well as the brass ones, but are presumably less durable in the long term. But then they are easily replaceable. There is not much difference between the two methods in the ease of getting a satisfactorily smooth-sliding fence. However, some people might not be able to get hold of 1/8" x 1/2" brass bar as easily as they could get polythene cutting board, and they might not happen to have a 1/8" bit for cutting the grooves for the brass bars; the polythene bars can be cut to suit whatever sized router cutter you happen to have for routing the grooves.

So the conclusion is: You pays your money, and you takes your choice.

Originally posted by gatiep
A way to strengthen the thread would be to tap the jarrah as u described, then remove the tap, blow out any dust and run some thin cyanoacrylate (super glue ) into the thread. Once that has set, screw the tap in to clean up the original thread.

That will make the thread as solid as you can wish for.

Cya

Joe


Have fun............................keep turnin

Joe,

I don't mean to shoot you down, but this probably won't work with the super glue. Cyanoacrylate glues are "anerobic" meaning they cure in the absence of air. You have to hold two parts together and expell all the air. Loctite products work the same (that's why the bottles are never full).
You could try Loctite Shaft & Thread repairer. Its an aluminium putty. Or an epoxy adhesive like Araldite. Never trying it myself.

Glen.

It really isn't necessary to take any special measures to strengthen the thread if you use a hard hardwood like jarrah. I just use a little wax to lubricate the threaded rod and find that the thread works just as well as it would in metal.

I don't care what the others say

I received your drawing and instructions on how to make the mortise jig and I am looking forward to starting it

Thanks Joe (Sharpie)

Me too
What sharpie just said, I mean.
Oh bugger, that doesn't make any sense either.
What I mean is I received Rocker's excellent plans and can't wait to start either.
Thanks Rocker.
Jim
ps Rocker, why did you sell your router table and your incra jig?
Was it because you have lost the faith and now use a table saw for tenons???

Originally posted by Glen Bridger
Joe,

I don't mean to shoot you down, but this probably won't work with the super glue. Cyanoacrylate glues are "anerobic" meaning they cure in the absence of air. You have to hold two parts together and expell all the air. Loctite products work the same (that's why the bottles are never full).
You could try Loctite Shaft & Thread repairer. Its an aluminium putty. Or an epoxy adhesive like Araldite. Never trying it myself.

Glen.

Hi Glen,

I seriously question the anearobic bit, because cyano is packed with nitrogen or other inert gas filling the excess space in the container. The reason why you hold the two together is because cyano is NOT gap filling. I'll give you an example further down about bicarb. Actually water/moisture sets it off like a rocket.

The principle employed with the threads are that the cyanoacrylate seeps into the wood, mainly capillary action and with the moisture it sets off and becomes hard. That way the threads are much stronger. The best product to use to 'kick off' cyano faster is just water vapour, or dampen the two pieces of wood that you want to join. You'll actually see a white substance at the joint. That is also the reason why cyano ( special grade0 is used in surgery.
Get hold of a bit of bicarbonate of soda or baking powder and add a drop of cyano on it. (Do in well ventilated area). You'll see a bit of smoke as it sets off, due to the moisture content ( Being a retired chemist I can guarantee you that the bicarb has some H20 knocking around), resulting in a hard lump that is very difficult to break.
This is what we modellers use as a gapfiller in building R/C airplanes with balsa or even GRP. We regularly tap a thread into spruce or even good quality ply, run cyano in as I described earlier on, then clean the threads.
I guess if two 6 mm bolts screwed through 6 mm ply , treated as described, hold on the wings of a r/c plane doing over 100 k per hour, doing aerobatics, it will hold the router jig in question.

Regards,
Joe