Router bit of-the-month (February 08)

This month, I am not highlighting an actual bit, but something that can make the difference between a bit, or a jig etc being usable, and not being able to do the job required.

The bit this month is in fact a router bit extender. I am certainly not condoning the use of router bit extenders for every operation, but in some instances, for some jobs, they are a much better solution than the alternative. (Shown here with a router bit fitted).

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This version of the router bit extender is quite impressive. It is made by CMT (an Italian router bit manufacturer) who are well renowned for the quality of their router bits. Here in Australia, CMT bits are supplied by Carbatec.

The concept is pretty simple – have a shaft the diameter of a normal router bit to mount in the router, then some form of mechanism to hold the router bit itself, and in this case, CMT have opted for quite a traditional style router bit collet, which is reassuring given that it needs to tightly hold the router bit in the extended position.

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This is the extender broken down into its individual components (not all extenders can come apart like this) Working from left to right, we have the collet outer ring, which screws into the collet base (part 3). Inside each of these is a cone which matches the cone on either end of part 2. Part 2 is the split-ring router bit holder. As the collet is tightened, the split-ring is squeezed together, gripping the router bit. The cones facilitate this, as well as ensuring the bit is maintained in the centre of the mechanism. The final part (4) is the 1/2″ shank which is fitted to the router’s collet.

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There are a number of occasions where the extender can be a god-send, and it is useful having one in your collection for if/when it becomes needed. These include, needing some extra plunge length, when using the router with a jig where the router doesn’t have sufficient plunge capacity to expose enough of the bit, and for bits that have too-short a shaft (to name a few). Some people also use them religiously with their table-mounted router because of a combination of too thick a table and/or too short a router bit and/or insufficient plunge capacity of the router and/or because they want to be able to change router bits above the table.

My personal preference is that these extenders are only used when they are justified, and there isn’t another solution (like purchasing a longer shanked router bit if that becomes a regular problem, or getting a router that can inherently do above-table bit changing). There is a reason router bits don’t come with an extra inch or so of shaft length (just for the convenience), and it isn’t because of cost (well that’s not the major reason). They do increase the load on the router bearings – there is a lot of extra leverage caused with the extra length. If you are running a Festool (triple bearing), or a Triton, then the router should cope, but not all routers are as strong. Remember too, we are talking about a high-speed rotary tool here (up to 20000RPM).

So the bottom line is, for a particular job, a router bit extender can be invaluable. I’d rather use an extender, than not properly inserting the router bit fully into the collet for example. However, it is not for every job, and in particular, it is strongly recommended that you don’t use one when the router bit exceeds 40mm diameter. This rules out panel raising bits!

Finally, here’s something a bit exciting for Stu’s Shed (and I’m hoping we can do more of this in the future, but it will depend on how successful it proves!) The CMT Router Bit Extender featured here was generously supplied by Carbatec, and is normally $79 (inc GST). For this month (Feb 08), if you tell Carbatec that you saw it featured on Stu’s Shed, then you will be able to purchase it for $69 (inc GST). (That’s almost 15% off). This offer has been made by Carbatec only for Stu’s Shed viewers. (Cool huh!)

One Response

  1. can u send pict of bits and there specific uses

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