box jointing router tips

[makaze]

Hi, due to poor instructions I could do with a bit of help.

I am routing 12.7mm box/finger joints and while my first attempt has produced an OK box the process has left me with a few questions.

I am routing 2 pieces of 18mm ply at the same time, the bit has a 6mm shank. I had quite a lot of spelching at the start of the cuts, the backing piece seemed to prevent spelching at the rear.

Should I have undertaken this route with multiple passes, if so how many?
What speed is best, my B+D has 1-6 speeds (not sure what they actually mean apart from 1 sloqwest 6 fastest).
I have read somewhere that it maybe best to cut the routes 1mm or so deeper to they fit perfectly when the overhanging bits are sanded down. Is this right? I tried to route to the 18mm depth and on the whole I'm nearly satisfied.

Thanks for any input.

Tom.

 

[longinthetooth]

You've chosen possibly the worst material to do this in! Unless it's birch ply? Anyway use the highest speed setting. Try clamping sacrificial anti-spelch pieces both front and back. Do it in one cut unless the router slows down a lot which affects the finish - speed wins! Yes add 1mm if you want, or maybe 0.5mm will do.

The anti-spelch pieces don't have to be as thick as the work, but go too thin & they're less effective.

 

[rafezetter]

I've been planning on making some box joints in 6mm thick mahogany ply (hobby storage boxes), so I'll do as you suggest and add sacrificial bits front and back, however as I'm going to be doing quite a few using the same bit and ply, would I need a new sacrificial each time or would using the same be ok, with the theory that as long as the new cuts are the same shape and size as the sacrificial hole the edges of the new cuts will still get support?

If I was going to do this a lot and make a sort of sacrificial support template; would a bit of solid hardwood be better for crisp cut edges?

(I've also just bought a trend credit card sharpening stone to sharpen up my carbides just to be sure.)

 

[Bluekingfisher]

A couple of points - a 1/4 inch shank on your bit will cause a little more (a lot more actually) vibration on the business end which translates to chipping of the timber. If you have a 1/2" shank then use that. A 12.7mm finger joints is a fair amout to rout with the cutter you have so take it slowly (not the router bit speed, your action)

Another tip I learned, when cutting plywood (even quality birch ply) treat the parts to be cut with super glue. smear it across then let dry this will bind the fibres together resulting in less chip out. A thin coat of expoxy will also work well. Failing all this a couple of coats of thinned down PVA will help, just not as good.

 

[Eric The Viking]

If you made one of the common jigs (vertical fence, slot and peg), you don't really need to worry about tearout very much:

The joint can be assembled either way round. Assuming you've been careful in setup and use, the back of the piece (against the fence) is automatically protected by a zero-clearance fence - you cut that when you do the first slot! That's your clean outer side for the finished item.

Regarding the other side, facing the cutter initially: When the cutter touches the work, it's going sideways. It should be pushing the work towards the index peg. You shouldn't really get breakout "vertically" (above the slot), unless the cutter has a chipped/blunt corner - it should cut like a rebating plane, but the speed renders a spur unnecessary.

If it is stubbornly breaking out at the top, you can use a marking knife across the workpiece to pre-cut across the outermost fibres. Use that side for inside the finished piece, so the lines are hidden (diligent measuring and setup are your friends here).

'Horizontal' breakout can only happen on the side nearest the pin (at the front), at the point when it starts to cut the maximum width, half-buried in the work. That can be helped by a sacrificial piece on the front, but if you're using that side for inside the joint, it'll be invisible when it's finished.

As others have said, move it into the wood slowly. Once you're past half of the cutter in the work, it shouldn't break out. Although people do cut two or more pieces at a time, bear in mind that any movement/vibration is mechanically amplified on the outer pieces, adding to breakout problems etc. If it's held solidly, no worse problem than one-at-a-time, but if you're unsure of the jig's rigidity, you're in for a nightmare of combs that don't fit together, inexplicably. If in doubt, do it in ones.

Clamp to the fence, tightly and as close as you can get to the cutter, whilst keeping clamp metal out of the line of fire - that also helps. Yes, you can hand hold, but clamps are better, and safer too.

Hope that's useful,

E.

PS: I haven't tried one yet, but I'd bet a spiral upcut* would work really cleanly.

*I think! I mean pulling toward the router, anyway, like a twist drill.

 

[makaze]

Many thanks for the replies.

My B+D router only has a max 8mm shank. I can only find a trend 12.7mm round over with 8m shank. I' m not sure of their quality though and the cdj 600 has obvious flaws just by judging opn common sense.
The router jig is a trend cdj600, I have screwed it to a piece of 18mm ply (4 small screws as provided) with a batten underneath which was secured into a B+D workmate, into open jaws and the tightened. I think this is not the way to go and I think was the cause of excessive vibration.

From replies I think I was going into the cut too fast, I have so little over hang on the comb it was hard to get the cutter ready to push. So a front piece to prevent the spelch is not an option.

I am going to try a better way to secured the jig to ply by cutting larger and more securing hole and use machine bolts, and also improve ply to work bench fixing.

I have tons of superglue and will try that to. I think 1 piece at at time may me a necessity.

Many thanks.

 

[Bluekingfisher]

Good luck with it, unfortunately box joints are just one of those operations that if not done correctly can permeate the faults the further alongthe board you go. If you are having problems still then try to avoid cutting wide boards (over 150mm) as any fault will magnify the further along you go.

 

[Eric The Viking]

My post above assumed a router table, as that's how people commonly do them (or cut them by hand).

If you have, or are thinking of making, a router table, the jigs for a table are probably an easier solution than a dovetail jig of that Trend type (IMHO - opinion sharply divides on this one!) - for box joints, I mean (not dovetails). Steve Maskery has a video online of how to make a jig (can't remember if its Youtube or Vimeo - if he picks this up, he'll say)

You'll get 8mm shank cutters from Wealden, and they're good quality. The thicker the shank, the less vibration.

Given it's box joints, you should be able to use a backer board with the Trend jig. If you screw a small lip to the top edge at the back, you can probably stop it falling out as you tighten up the wood! I've got a similar jig, but gave up in exasperation as it was so awkward to set up.

We all go through the same process of frustration, leading to satisfaction when we eventually crack the problem!

E.

 

[Steve Maskery]

Steve Maskery has a video online of how to make a jig (can't remember if its Youtube or Vimeo - if he picks this up, he'll say)

Blip - there was a 10 minute limit on YouTube at the time.
http://blip.tv/workshopessentialscom/fi ... ig-3225447
Enjoy
S

 

[mailee]

I always use an up cut spiral bit when cutting box joints as they do give a cleaner cut. I also use a sacrificial board at the front and the fence at the rear and this gives a clean cut. I should add though that I only use solid wood and not ply. HTH. :wink:

 

[Reggie]

My post above assumed a router table, as that's how people commonly do them (or cut them by hand).

If you have, or are thinking of making, a router table, the jigs for a table are probably an easier solution than a dovetail jig of that Trend type (IMHO - opinion sharply divides on this one!) - for box joints, I mean (not dovetails). Steve Maskery has a video online of how to make a jig (can't remember if its Youtube or Vimeo - if he picks this up, he'll say)

You'll get 8mm shank cutters from Wealden, and they're good quality. The thicker the shank, the less vibration.

Given it's box joints, you should be able to use a backer board with the Trend jig. If you screw a small lip to the top edge at the back, you can probably stop it falling out as you tighten up the wood! I've got a similar jig, but gave up in exasperation as it was so awkward to set up.

We all go through the same process of frustration, leading to satisfaction when we eventually crack the problem!

E.

I assumed this was for a router table too

Along with all the power tools that I've had donated to me recently, there is a box/dovetail joint jig that looks very similar to the trend, I haven't used it myself but my dad did a test on a pair of bits of pine and the joints are perfect, so I think if everything is setup correctly then it should be great.

From what I've been told, if you're using a guide bush, then you need to either make sure the router bit is dead centre in the bush or if you can't get it dead centre, make sure that you keep the router orientated in the same direction throughout the routing process, otherwise you'll introduce errors no matter what, if you're using a bit with it's own bearing you don't need to worry about it because the bearing will make sure that no matter how you approach the wood, the centre of the bit will always be at the same distance away from the template.

Btw. why is plywood one of the worst materials to do box/dovetail joints with? Is it because no matter what the orientation of the work piece, you're always cutting with and across the grain through the successive layers, or does the glue in the ply make the bit have to work harder? Is that why I've seen a few bit manufacturers making bits specifically for plywood?

that workshop essentials jig is pretty neat, I designed a jig in sketchup almost the same except mine doesn't have the dust extraction.

 

[Eric The Viking]

From what I've been told, if you're using a guide bush, then you need to either make sure the router bit is dead centre in the bush or if you can't get it dead centre, make sure that you keep the router orientated in the same direction throughout the routing process, otherwise you'll introduce errors no matter what, if you're using a bit with it's own bearing you don't need to worry about it because the bearing will make sure that no matter how you approach the wood, the centre of the bit will always be at the same distance away from the template.

That's sound advice.

My big router (T11) came with a centring tool for 30mm bushes (the kitchen worktop jig size), but the small Bosch didn't. To get around this I use a Trend auxiliary base ("Unibase"), that came with alignment tools for 1/2" and 1/4" collets. It works on the basis that, once you've got the aux base centred on the shaft, the bushes will be also.

That's probably true, but it depends on the machining accuracy of both base and bushes. And that's not guaranteed. My first attempt at box joints involved a 1/4" cutter, and the 1/4" comb for the Axminster jig. There's a tiny and awkward guide bush that's barely 3/8", with an internal diameter very close to 1/4". Within 20 minutes, I'd managed to remove this flange from the plate by reaming it out with the cutter!

Btw. why is plywood one of the worst materials to do box/dovetail joints with? Is it because no matter what the orientation of the work piece, you're always cutting with and across the grain through the successive layers, or does the glue in the ply make the bit have to work harder? Is that why I've seen a few bit manufacturers making bits specifically for plywood?

Several reasons: grain direction alternating (so you can't win), glue, loose laminations, voids and non-wood inclusions. Then the risk of chipping off the top layer when you fit it together, and finally a nasty sanding job if you don't cut the combs exactly the right length in the first place.

I'm not an expert in routing plywood, but my few experiments have been disappointing compared to, say MDF of the same thickness. For example:

These compasses are about 10" long and a first go at making my own tools (they've turned out more useful than I expected). The cross-brace, which clamps up to hold them open at a set distance, is made from what I think is 3/16" ply. It's from an old offcut of five-ply (interior grade birch - best quality when it was new, umpteen years ago).

The first attempt was to make a quadrant in the traditional manner. I cut it well enough on the router table*, but the vibrations loosened the laminations and 1/4" round the outside wasn't enough. It disintegrated after I'd fitted it to the compasses. The straight version, incidentally, works far better, although you can't put a simple measurement scale on it as blacksmiths of old did (a quadrant's distance scale would be equal arc sections, in inverse proportion to how far up the legs it was fitted, but they are inherently inaccurate).

Back at plywood: You can rout the edges of shapes, but half of the thickness will be cross-grain and half will be ripping (assuming you're going straight along a board, but you get the idea), that means there's no ideal cutting speed - if the cutter RPM is right for one, the feed speed won't be for t'other, and vice versa. Arguably my cutters are well used and fairly blunt, but I always end up burning some of the laminations at some point in cutting a complex shape. So then you get the awkward decision of how much oversize it needs to be, to allow for sanding the burns off. Yup, I'm definitely an amateur at all this! Still, I recently won a Bosch POF 600 on eBay, which is the vari-speed version of my old faithful 1/4" router. I think getting the cutter speed just right may well help.

I know: people do it all the time, and I ought to invest in an upcut bit, for that purpose, etc...

E.

PS: Quite coincidentally, those are octagonal box joints in the picture, that the compasses are resting on. They were machine cut on a home-made jig on the router table. "3D" box joints are an even worse can-o-worms, and doing those was a nightmare (took me a long time to work out the jig, never mind make it function!). Still, it proves it can be done (those are 1/4" fingers).

* I found the trick was to do the slot first, obviously (by dropping-on), then creep up on the outer shape (coping saw) and finally drill the pivot hole. I'm not a router-nutter either: I did try the slot by hand with a fresh blade in a coping saw too, but I couldn't get the finish clean enough, and sanding it is nigh-on impossible (the sandpaper rips splinters off the face laminations). Ideally it's a job for a scroll saw, wot I don't possess.

 

[Reggie]

So the wood that all beginners go to ends up being one of the hardest to work with on a router, that's typical

I immediately thought scrollsaw for that slot, it'd give a nice clean cut with minimal sanding, which is reminding me I need to clean my scrollsaw's table :-(

One thing that struck me with all of the box joint jigs, whether it's a commercial standalone jig, or one of the leadscrew based units or just a simple finger/gap sled jig, they all require a small amount of crucial setup but can all produce decent joints.

 

[rafezetter]

More good advice I'll def be using when I get round to it.

Here's my link for steve's box joint jig - different from the youtube one @ 19 mins long, and almost the main inspiration for me to make a router table in the first place:

http://lumberjocks.com/topics/14531

not sure why you had a problem with making an octagonal box jig - Erik - surely a backer wedge cut to the right angle and fed thru as normal would have been enough, and if you wanted to get really fancy you could make a hinged version with locking bar like a tapering jig for legs but upright to get different angles, have the front part of the backer split so the bottom half is sacrificial, screwed to the top half and voila! If you do different angles often write on each sacrificial what angle (how many sided box) it's for and swap out as necessary.

"What about clamping!!" I hear you cry -... hehe try these on for size and would work great for 90 deg box joints too on a homemade jig - no worry about any metal or plastic damaging the cutter:

https://www.ukworkshop.co.uk/forums/viewtopic.php?t=18192&highlight=
and
https://www.ukworkshop.co.uk/forums/viewtopic.php?t=20448&highlight=

adapt and make em a bit smaller.

yeah you know it

love the dividers btw - great job

 

[Eric The Viking]

... not sure why you had a problem with making an octagonal box jig - Erik - surely a backer wedge cut to the right angle and fed thru as normal would have been enough, and if you wanted to get really fancy you could make a hinged version with locking bar like a tapering jig for legs but upright to get different angles, have the front part of the backer split so the bottom half is sacrificial, screwed to the top half and voila! If you do different angles often write on each sacrificial what angle (how many sided box) it's for and swap out as necessary.

Ah. Perhaps I ought to let you experiment for a while... (he said, looking for a smiley with a twisted evil grin).

I didn't really explain, partly because I was intending a proper write-up some time. Assuming the jointing isn't symmetrical across the workpiece, once you deviate from either 90 or 180 (I know, nobody uses them that way!), you need four types of end, not two. So, say you have an octagonal tray with a rounded-over top edge, that's four sorts of pieces to make. I don't think it can be done on the conventional type of router table jig, as that can only cut two ('pins and tails' if you will. And a wedge is a really bad idea on its own, because you have to index the stock in two planes now, not just one, and it won't let you hold it anywhere near precisely enough.

You could, I suppose, use a splining jig and plane off the unwanted triangles after assembly, effectively cutting the 22.5 deg corners afterwards. That would possibly eliminate some of the issues. In fact it might be a good way to go. The issue there would be getting absolutely spot-on alignment of the cutter and the indexing key in the bottom of the jig's 'box.' I'd have to think about that one for a bit, but some sort of adjustable peg might be practical.

I tend to be far too linear in my approaches to the sequences work is done in. When I did those, and the jig design relied on this, I cut the mitre angles first. Whilst it works, it's not at all easy. Hmm... spline box...

love the dividers btw - great job

Thanks. they're the tidiest tool I've made - beech from an old telephone table (remember those - from when we had 'telephones'?). The point is a masonry nail, with the end ground off (Proxxon), chucked in the pillar drill and pointed against an old diamond plate. It's held a very sharp point really well - glad you can still get wine corks! By happy accident, it also folds up nicely for the 'measuring tools' drawer. If it had a quadrant, that would stick out.

E.

 

[rafezetter]

You could, I suppose, use a splining jig and plane off the unwanted triangles after assembly, effectively cutting the 22.5 deg corners afterwards. That would possibly eliminate some of the issues. In fact it might be a good way to go. The issue there would be getting absolutely spot-on alignment of the cutter and the indexing key in the bottom of the jig's 'box.' I'd have to think about that one for a bit, but some sort of adjustable peg might be practical..

I'm obviously missing a trick required in practice that isn't so obvious in theory - this (linky below) is the kind of thing I had in mind, yes I should have mentioned to cut the base mitre first so that the base of the wood going thru the jig is flat to the table, but to my eyes from the mockup drawing shown; a wedge backer at the correct angle with locating pin as per 90deg would work.

http://sawdust.online.fr/SpindleMoulder/FingerJoint/en_Octagon.php

But I've never done it, and as yet no table to fiddle with it myself otherwise I'd have given it a try for it's own sake, unless you'll let me come play in your workshop pretty please?

A write up would be appreciated when you have some time outlining the realities of such a jig for angles other than 90deg.

A splining jig with contrasting infill's the same size or similar as the fingers would look very attractive as well, and possibly simpler than finger joints; do as a wider version of a mitre spline wedge.

 

[Eric The Viking]

It's a different set of problems with a spindle moulder - more akin to a table saw I suspect. He's also "cheating" in that his pieces have rotational symmetry, not mirror.

Also, mine fit as-cut, with no planing afterwards, although I do now think planing down is probably the way to go instead. You could cut them like a spindle, using a biscuit cutter and a 45 degree mitre fence, but the issue is pin alignment. My T11 will easily adjust the cutter height to 1/10mm, but I'm not sure that's good enough, and anyway the shank of the cutter will limit the thickness of stock you can joint (same but not so severe on a spindle I guess).

The reason jigs like Steve's work so nicely, is that, once set up, you just push the stock through without further thought other than holding tight and keeping fingers out of the way. But that's only good for square corners :-(

My own table saw isn't running presently, and hasn't been for a while, so it wasn't an option when I was doing them. I don't think making a TS jig would be easy, but it probably would yield cleaner results too. It's the same issue as a biscuit cutter though - either your fingers are as wide as the saw kerf, or you make several cuts per slot.

I ought to try the biscuit cutter idea, as I have a couple of them - otherwise pretty useless things apart from grooving. In my experience they aren't a patch on a genuine biscuit jointer.

E.

 

[rafezetter]

Ahh I see - I hadn't realised you were going for "end finish" cutting, I was thinking more as you say; cutting to get it to work then trimming accordingly, and I can see how mirrored joints would look much cleaner.

I wasn't really taking the spindlemoulder into consideration as I'm sure I've seen spline jigs for a tablerouter somewhere on my extensive websurfing, with no proper tools it's about all I can do to satisfy the craving, (problem is it just ends up giving me more ideas of "oooh I'd like to try that!").

lol 4am reply you're as bad as me

 

[Eric The Viking]

Ahh I see - I hadn't realised you were going for "end finish" cutting, I was thinking more as you say; cutting to get it to work then trimming accordingly, and I can see how mirrored joints would look much cleaner.

I think you have to do that, for appearance. Otherwise, it looks really odd, especially on something small (mine were for a bird table, about 15" across).

I wasn't really taking the spindlemoulder into consideration as I'm sure I've seen spline jigs for a tablerouter somewhere on my extensive websurfing, with no proper tools it's about all I can do to satisfy the craving, (problem is it just ends up giving me more ideas of "oooh I'd like to try that!").

lol 4am reply you're as bad as me

Spline jugs, I think, are standard workshop tools for many box makers, but I'm not one (yet), so I haven't made one (yet).

(Should've been 5AM. I suspect the forum may not be on BST. Couldn't sleep and I'm supposed to be commissioning a Ubuntu server which was humming its displeasure all night on a chair in the dining room. Bad-tempered things! You can't just leave it there with that console prompt...).

E.