If you’ve made a router table (← check that link to see how to make one) or a small homemade spindle molder with your plunge router, or if you’re thinking about making one, you may have noticed (or should know, depending on the case) that when placing the router under an 18mm thick table, the bit may not stick out far enough above the table.
One option is to use a thinner board, about 10mm (which we may need to reinforce around the router to prevent deformation). Even then, the bits may not reach the desired height. We can always extend the router bit shaft into the collet less than the recommended 3/4 of its length, although sometimes this may not be enough and it’s not advisable to leave too little of the bit shaft in the collet.
The best solution to make the most out of our homemade spindle molder is to use a collet extension like those made by CMT. Yes, it’s an additional expense. Or rather a few small additional expenses, because if we look at the CMT catalog, we will need to buy several parts.
But keep in mind that, especially with larger diameter bits, it can cause a lot of vibration and the noise may discourage its use.
So far, I haven’t needed to use these collet extensions, as my bits have always protruded enough above the table. I admit that this is partly because the router I use, a Power Plus X093, allows the use of 12mm shank bits (and came with a set of these bits) and these are somewhat longer than the cheap sets of 8mm shank bits I have.
The router that many of you will have, and also the first type of router I had, in many cases will be for bits with a maximum 8mm shank. And you probably have 6mm and 8mm collets. With these routers, you cannot use bits with a 12mm or 12.7mm (1/2″) shank and there isn’t a collet extension for 12mm or 12.7mm bits that you can insert into an 8mm router collet.
These routers often come with a bit set, and if they don’t, I recommend buying at least one cheap bit set. I have a couple; one is the typical set that you see everywhere and often comes included with many routers, and the other, which I don’t remember where my father got it from, is a more complete set that curiously includes slightly longer bits.
For routers that accept a maximum of an 8mm shank collet:
To get the bits to reach the desired height in the homemade router table, a solution, as mentioned above, is to use a collet extension like the ones from CMT. These consist of a reduction and the collet extension itself. You can see in one of the photos the parts: reduction, collet extension, collet, and nut. In this type of extension, the largest collet that can be used is 9.5mm (3/8″), and it is not possible to insert larger diameter collets. Neither the 12mm nor the 12.7mm collets fit inside the extension.
Here are the necessary parts, references, and prices I found as of today (May 2014):
You need a reduction, a collet extension, and the collets:
Prices are outdated
Shank diameter reduction S=8mm and metric M10 -> 797.580.00 -> €11.18
M10 metric collet extension -> 796.100.00 -> €18.97
You will be able to use collets for the following shank diameters:
6mm -> 796.560.00 -> €6.15
6.35mm (1/4″) -> 796.564.00 -> €6.15
8mm -> 796.580.00 -> €6.15
9.5mm (3/8″) -> 796.595.00 -> €6.15
When I bought the collets, they didn’t have the 6.35mm one, but they offered me an adapter that transforms the 8mm collet into a 6.35mm one -> €8.30
WITH THIS 8MM SHANK COLLET EXTENSION, YOU CANNOT USE COLLETS FOR 10mm, 12mm, OR 12.7mm SHANK BITS
And in case you were wondering,
the collets from your router DO NOT fit into these extensions ( nor do the collets from the extension fit into the router collet), so it is necessary to also buy the required collets according to the shank diameters you have or think you will have in the future.
