How do I cut a rebate following a curved edge on a router table?

[Droogs]

If you are using a router with a tail, then you want one of these base plates:

https://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/arched_fluting_jig.html

 

[Droogs]

If you are doing it by hand then you need a quirking plane or an ultima 728

 

[AndyT]

If you are doing it by hand then you need a quirking plane or an ultima 728

Or for anyone confused by autocorrect, an Ulmia 728

 

[custard]

This is a job that I do fairly regularly, here's a summary of how I normally go about it.

This is a three drawer desk early on in the build. Look at the curved front edge. You can see that a curved, solid wood lipping is joined to a curved veneered top. I'll normally route a 1mm groove along that joint line and insert a contrasting line of Holly or Sycamore inlay. Okay, it's on a smaller scale than the work you envisage, but the principle is exactly the same.

There's no need for a router table, on a job like this you need a bearing guided cutter in a hand held router.

You need a curved template that EXACTLY matches the groove that you want to cut. Here you can see the curved template clamped to the top of the desk and you can see how the bearing on the cutter will follow that template.

Cutting the grooves for the inlay at the back and the sides is much simpler because these are straight lines rather than curved. So I can just use the router mounted in a track. The track means the router can't deviate from its prescribed course, in fact if you look closely you can see there are stops clamped on the the track which designate the start and end points for the cut. So this cut is pretty much risk free. The curved cut however requires you to be paying full attention! I'd suggest making the cut in a number of shallow passes.

And here's the finished job, where you can se the inlay lines running all the way around the top.

 

[custard]

If you are doing it by hand then you need a quirking plane or an ultima 728

I used to use one of those Ulmia 728's but never really got on all that well with it. The one I had wouldn't lock off securely, so you never knew if the fence was going to slip half way through the job...which could then mean many hours of work getting flushed down the toilet!

Those type of tools are called purfling cutters, and many of the commercially available versions that I've seen are a bit dodgy. I guess maybe it's because its traditionally a craftsman made tool, so manufacturers perhaps don't feel they have much of a budget to play with?

Karl Holtey made an absolutely beautiful purfling cutter which was sold by Veritas as a limited run. I decided to treat myself and needless to say, like anything that Mr Holtey makes, it was absolutely impeccable.

I subsequently wanted a few differently sized cutters, so I contacted Karl Holtey to see if he might make something up for me. A few weeks later a whole range of alternative cutters arrived in the post and he wouldn't accept a penny in payment. To call him a national treasure doesn't go nearly far enough!

When I help out someone on this forum it's because so many people, like Karl Holtey, have helped me with my woodworking over the years, so it's only right to "pass it on".

 

[Peri]

You need a curved template that EXACTLY matches the groove that you want to cut.

Sorry if its a stupid question - how do you get the curved guide in the first place? Bandsaw and spokeshave/sandpaper?

 

[custard]

Sorry if its a stupid question - how do you get the curved guide in the first place? Bandsaw and spokeshave/sandpaper?

That's a great question. Before CNC machines became commonplace there was a whole area of cabinet making skills that was just about how to make all the curved templates that you constantly need.

On the example I previously gave there's a great trick that produces the gentle curves of extremely large radii. You basically make a very flat triangle and mount a router at the apex. You sink a couple of brass pegs into a sheet of MDF and by running the "triangle" against these two brass pegs you can cut an accurate curve of whatever radius you want, adjusting the dimensions of the triangle gives a different radius curve. There's a cunning bit of geometry that provides the necessary formula. This photo shows the technique in action.

These days it's usually easier to just get these templates CNC'd, but I still frequently use the older manual techniques, partly to keep my hand in, partly because it's cheaper to do it yourself, and partly because sometimes you can't wait while somebody turns the job around.

So in answer to your question. At the beginning of the job you'd make up a master template for each curve in the design. Some you'd make by simply bending a flexible steel ruler or a wooden lath between two points and tracing out the resultant curve (that's the bandsaw/spokeshave solution that you mentioned, quick and dirty but not ultra accurate), other curves that need to be particularly precise you'd use more esoteric techniques like this one.

This is part of a whole body of knowledge that younger cabinet makers just aren't taught anymore. For example there's a really clever trick that allows you to make absolutely precise male and female versions of any particular curve (think about it, that's actually phenomenally tricky to achieve), I've never seen this trick detailed in any book or on the internet, but most cabinet makers over the age of about forty or fifty were taught it when they were younger. Sadly most younger cabinet makers wouldn't have a clue and are therefore forced into CNC based solutions.

 

[Jester129]

I get the triangle idea, truly impressive!

 

[machone]

Okay, it's on a smaller scale than the work you envisage, but the principle is exactly the same.

My woodwork is more on the ‘murdering a piece of teak’ scale. It is part of a hatch surround for my old Dutch steel sailing boat that I am refitting. I actually feel bad somebody better is not working the wood but it is the best type for that use. Your work is truly inspirational/aspirational. Whenever I see fine woodwork I am always amazed at the clean areas, smooth curves and perfectly squared stock and no gap joints. Beautiful.

Which method did you use to cut the template on the desk? Was it cnc or the big triangle?

 

[Peri]

........but most cabinet makers over the age of about forty or fifty were taught it when they were younger. Sadly most younger cabinet makers wouldn't have a clue

Sadly it's the same in engineering.
I work at a college where we teach turning, milling, welding, bench fitting and welding. I'm very far from being an expert in any of them, but most of the older lecturers simply amaze me with the amount of knowledge they have. Generally they've been on the tools for many years before they came to teaching, and no matter what you're trying to achieve, they'll have a trick or two to get the job done.

Unfortunately, in the last decade we've lost probably 80% of those guys - many of the new 'teachers' we get have never even done practical work, coming straight from university with clean hands.

From a 'teaching the next generation' perspective, so much is being lost, it's actually quite scary.

 

[Yojevol]

Sadly it's the same in engineering.
I work at a college where we teach turning, milling, welding, bench fitting and welding. I'm very far from being an expert in any of them, but most of the older lecturers simply amaze me with the amount of knowledge they have. Generally they've been on the tools for many years before they came to teaching, and no matter what you're trying to achieve, they'll have a trick or two to get the job done.

Unfortunately, in the last decade we've lost probably 80% of those guys - many of the new 'teachers' we get have never even done practical work, coming straight from university with clean hands.

From a 'teaching the next generation' perspective, so much is being lost, it's actually quite scary.

It was probably about 16/17 years ago that the government decided that the standard of further education needed improvement. This was to be done by ensuring every teacher/tutor/lecturer had an appropriate teaching qualification. Many ex craftsmen were forced into taking courses to get the 'piece of paper'. The alternative was redundancy. Many, including me, took the latter option so depriving the system of their wealth of knowledge.

@custard
Can you let us in on the male/female pattern method? I only know of the router with an inside/outside follower bush method.
Brian

 

[custard]

Which method did you use to cut the template on the desk? Was it cnc or the big triangle?

I used the "big triangle" method. If the template will only be used to make a small number of components then I usually make it from MDF with the "big triangle" method. But if the template will be used to make lots of components then it makes sense to have it CNC'd in a more durable material.

I'm impressed with your Dutch Barge project, I used to live by the Thames in London, and there were quite a few steel Dutch Barges used as houseboats, when they were well maintained after they looked magnificent!

 

[Peri]

........ensuring every teacher/tutor/lecturer had an appropriate teaching qualification

Strangely, our college would jump at the chance of employing time served staff with minimal teaching quals.

Our problem is, what skilled engineer is going to come and work where the starting salary is £23k, top whack would be £32, and there's been one, 1% pay rise in the last 11 years?

(sorry for the off topic Machone)

 

[HamsterJam]

UK engineering not just losing skills in education sector but worryingly in businesses too.
Senior management appear to think recruiting really bright kids with first class degrees is the answer but most (all?) will have no hands on experience.
I can see industry repeating a lot of old mistakes again in the future.