One to ponder, bit of a teaser....

[woodbloke]

Some years ago I saw maker producing a table for Linley. The top was the ususal 18mm mdf and it was going to be lipped before veneering. Having made the top, he then set about producing a set of template(s) to bearing cut the lippings, by using only a router, guide bushes and cutters to produce a perfect match. But how?
The process was very convoluted and involved changing bushes and cutters at least a dozen times before the final set was ahceived. The problem is that whilst one side of a router cut to a given radius will produce the desired curve, the farther curve will be a larger radius (by the dia of the cutter), which will not make a perfect fit when offered up. If a circular table is being produced, this is no big deal as you can simply adjust the radius of the router jig to the correct distance for the lipping...trouble is, this table was elliptical. I have been pondering on this one for ages,so....... can anyone work out the sequence of bushes and cutters to produce the template(s)? - Rob

 

[Paul Chapman]

Rob,

I can't remember all the details but I'm sure there was something in the American Fine Woodworking magazine about this. I don't buy the magazine often these days so I probably saw a demo of it on their website - but they delete the video clips after a short while. Basically the author (a female - can't remember her name) was lipping a curved board with solid wood and she demonstrated the method of making up templates so that you could use bearing guided cutters. I remember that it was quite hard to get your head around the method because, as you say, the two sides of the cutter produce different radii. If you know anyone who regularly buys FWW it might be worth looking back through them - it was about 6 months ago (I think :? ).

Sorry this is all a bit vague

Paul

 

[woodbloke]

Paul - I watched this guy make up the templates and asked how he did it and he casually replied that it was a... 'piece of p@%s' and proceeded to show me the scrap of paper with the sequence of cutters and bushes needed, about a dozen changes in all if I remember. When he was making the templates he had access to a complete set of Trend bushes and loads of different cutters but I just cannot work out how he did it ...infuriating init? -Rob

 

[Nick W]

Funny you should mention that right now, as it is what I am doing right now. I will be writing the project up for a magazine (not sure which yet), but the basic principle is:

Buy the Trend collar part no: GB/COLL/3054 and a 30mm guide bush and 12mm cutter if you don't have them.

When going round a template with the 12mm cutter with 30mm bush and 54mm collar the inner path of the cutter will be (54-12)/2 =21mm outside the template. Using just the bush and cutter the outer path of the cutter will be (30+12)/2 = 21mm outside the template too. So make the template 21mm smaller all round that the ellipse (or other shape) that you are after, and use the bush and collar when cutting the outer edge of the inner part, and just the guide bush when cutting the inner face of the lipping.

You'll have to wait for my article to see how I make up the lipping though, if I tell you that now I won't have anything to sell the mag. :wink:

 

[woodbloke]

Nick - that explains it....hope the article is in F&C - Rob

 

[Paul Chapman]

infuriating init?

Yes - but I bet the magazine will be a sell-out when Nick's article appears Must remember to keep that one :wink:

Paul

 

[Scrit]

You need to get yourself a copy of the Wadkin manulal on j=igmaking for pin routers. That explains the techniques used and came with every Wadkin pin router sold (like the one in my avatar.....)

Scrit