Box joint router jig

[RogerP]

I've made a router jig for box joints (finger joint, comb joint - by other names). It is working well using a 1/4" shank - 1/4" Wealden tungsten router but, whist it's pretty good, the cut isn't totally clean. Do you thing using a 8mm shank bit and/or HSS cutter instead of carbide would improve matters?

Roger

 

[Rob Platt]

How do you mean not clean?
I assume you have a sharp cutter the right speed and a sacrificial piece of timber behind to reduce breakout if necessary.
All the best
Rob

 

[Blister]

I use a sacrificial piece of timber behind and in front of my work piece to keep entry and exit cuts clean :wink:

 

[RogerP]

I was just wondering if HSS gives a cleaner cut than tungsten - albeit with a shorter sharp life. I'm probably being over fussy but the very small imperfections left by the router do show up quiet annoyingly on the finished joint. I must admit I'd not used a sacrificial piece in the front - I'll have to try that - thanks.

 

[Shrubby]

Roger
Are you using a straight cutter?
I cut my 8mm finger joints with a tct spiral and get good results in birch ply (it's a 2 flute metal bit - so not technically the correct bit for wood)
Matt

 

[RogerP]

I do have a spiral cutter so I will try that as well - is yours up or down cut?

 

[Chataigner]

Spiral cutter, definitely better - think about how the blade exits the material, if sharp, it should be much cleaner.

As for up or down, it all depends which way is up! If you have it in a router table, which I assume you do, then you want an up cut bit, which will be down cut in the table.

Bon courage!

 

[RogerP]

I'm in luck, the only spiral cutter I have in the size I want is an up cut

Thanks.

 

[CNC Paul]

Spiral cutter, definitely better - think about how the blade exits the material, if sharp, it should be much cleaner.

As for up or down, it all depends which way is up! If you have it in a router table, which I assume you do, then you want an up cut bit, which will be down cut in the table.

Bon courage!

Up cut will allways be relative to the wood, even if the cutter is up side down :? I wonder what they use in Aus.

 

[RogerP]

Up cut will allways be relative to the wood, even if the cutter is up side down :? I wonder what they use in Aus.

Dunno, but I see there are cutters with both up and down spirals on the same bit ... I'm confused enough already

 

[wcndave]

I use Steve Maskerys excellent box jig, and therefore have a back plate for each size of cutter.

I also use a £30 cutter, not any cheap ones that came with router...

I get very little tear out, if any.

I don't know if SM is watching, however i do find one problem with this technique. The ring inserts are very slightly lower than the cast iron table, so i get a different depth on the edges than near centre, and also some slanting issues - hardly notice, however i think i will change to a woodrat.

I recently tried to "go over" some cuts again on my finger jig, and ruined about 80cm of cherry board

on the woodrat you can also do a small cut from the rear first which should eliminate completely.

 

[RogerP]

I made new jig, used a sacrificially backing piece with a spiral cutter and now I'm getting close to perfect joints.
Thanks to all for the help.

 

[Benchwayze]

Roger,
Regarding 8mm shanks.
I don't think they would be better. I KNOW they would be better.

Less Vibration with deep cuts. I had the same problem with a Leigh Dovetail jig and that's how it was overcome.
Gathering dust these days though!

John

 

[wcndave]

I got my woodrat on friday, and by saturday lunchtime had set it up, and by 2pm had made perfect box joints. obviously it's rather expensive just for that, however i made perfect fitting variable spaced dovtails by end of day, and half blind dovetails today - and with using it for morticing / tenon joints, general routing, dados etc - i think it will prove a good buy...