There are router bits, and router bits. They come in a substantial number of shapes and sizes for a vast variety of functions.
Signwriting is a rather popular use for routers, given its particular ability to operate around curves and corners, its ability to follow templates and a router bit is basically a powered chisel.
Now chisels come in two types. Ones used to shape wood, and ones used to open paint cans. If your router bit isn’t razor sharp, you might as well use it to open paint cans – the difference between a sharp and blunt router bit is chalk and cheese. If you want a smooth, clean finish, the router bit needs to be as sharp as is achievable. Tungsten carbide is not the sharpest material possible, but because of its hardness and durability it is preferred for the cutting edge of router bits and saw blades.
Face it though, sharpening it is a bugger. Quality router bits are sharpened by CNC machines, able to produce polished carbide faces, but even a quality bit blunts with use. You can send a bit away for sharpening, but the way to really get as sharp as new, is to have a new router bit.
So where does that leave us?
The ideal is:
A router bit that is razor sharp
Tungsten Carbide tip for maximising durability of the edge, prolonging the amount of cutting when the bit can still be considered sharp
Cheap enough (after the original purchase) to replace whenever it dulls off
Still able to be sharpened to maximise bit lonegivity
Guess we really want our cake and get to eat it too!
I’ve been trying out a couple of router bits that hit all these points – the professional signmaking bits from ToolsToday, by Amana Tool, and in particular the Insert V-Groove bits, that have replaceable inserts.
Amana Tool Router bits
These are not bits for massive stock removal – there are bits with significantly heavier chunks of carbide for that operation. These are designed to achieve one particular feature – significant sharpness, and the ability to maintain that by easy tip replacement. The angle that they approach the work is also important – sharpness is only one part of the formula, and the angle of attack is also critical to avoid tearout.
These bits are designed for CNC machines, and router tables. So of course I turned straight to my ‘manual CNC’ machine – the Torque Workcentre.
My ‘manual CNC’
To try the bits out, I set up with the copy attachment, and chose a letter to duplicate as a first trial.
The 1/2″ bit is mounted (this is the 90 degree bit, #RC-1102, with the blade set at 45 degrees, the resulting groove is an exact 90 degrees. There is also a 91 degree version (#RC-1028) for ‘mitre folding’ – this is where you cut a groove, then fold the material at that groove – used in furniture making with melamine and the like to get a sharp corner, with the outer skin being continuous around the corner, and not with a cut at the very corner).
From the Wood Magazine website, here is an example of a box made with this technique. (You can do it with a 90 degree bit – a 91 degree bit just achieves a sharper corner)
First 2 passes, increasing total depth to around 5.5 – 6mm
The first pass went well, and a very clean cut. I then increased the cutting depth for a second pass. It comes down to how you use the Torque, but as a general rule this isn’t pushing the bit as much as a CNC will – it has a much higher feed rate tha what you’d tend to do by hand. Still, it coped well.
I then changed the copy pin to one with a wider diameter (from 1/4″ to 1/2″) and ran around the template again.
The bit cut really cleanly, and easily. Don’t judge the small indentations around the curves of the “S” – that comes down to the smoothness of my template. I can really see how well this would also work on an actual CNC machine.
If you want a fine cut, then the 45 degree bit is for you.
With a combination of the two bits, you can cut large solid letters, and fine, precise details.
And as they dull off (as all bits will with use), the cutting surface can be removed and replaced or resharpened as you desire, without having to incur the price of a new router bit.
Available from ToolsToday.com in the USA. Now you can have your cake and eat it too…or in terms of router bits, you can always have sharp router bits and use them too!
Originally posted on June 4th, 2012 by Stuart. Read the original article here