K Line on Wealden tenon router


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Established Member
2 Dec 2009
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Newport Pagnell
After a bit of advice!

I bought a tenon router cutter for using on my router table. I have a dewalt 625 fitted in an axminster router lift plate using an X-treme Xtension for easier above table changing.

Now to the dilemma.....

When installing the router bit it won't drop down to the level of the K line as per the photo.


Do you think this is still safe bearing in mind it wont physically go any lower?

Thanks for any advice!
I can't say what's OK or not (come in somebody that knows), but in the general sense the issue with shaft extensions is that they increase the risk of 'whirl' problems - especially if the cutter is heavy. They have to be very accurately made to avoid introducing more cutter run-out too.

Whirl is what happens if the shaft bends/deflects a little to one side - it takes the cutter out of balance, and the out of balance generates a centrifugal force that tends to bend the shaft even more. Which if the shaft isn't stiff enough is the beginning of a negative and self reinforcing spiral into more out of balance force and more deflection. Into the risk of something coming loose if it gets bad enough.

Whether or not there is a significant risk I don't know (i've never heard of a mishap in practice, and lifting a cutter too high in the collet to get height brings its own risks), but I have seen it suggested on a forum that it's unwise to use heavy/long cutters (what's heavy?) with extensions. There's a mention of the issue here, and the suggestion that care is needed not to overdo the feed pressure: http://www.mlcswoodworking.com/shopsite ... ollet.html
What happens if you remove the collet extension?

It doesn't strike me as a very good idea to use such a cutter with an extension, but I guess if you can't make deep enough tenon shoulders otherwise you've got a problem.

I have a T11 and initially had trouble with the lift mech 'bottoming' before it was high enough. A bit of dismantling later, I'd removed enough clutter (plunge depth stop adjustment screw, etc.) to gain almost 1/2" of movement upwards. I've never needed a router lift, nor any extension (so far), as a consequence.

I think the 625 is darn near identical to the T10, which itself only differs from my T11 in the shape of the base plate aperture. So, given the above, unless something else is preventing the router plunging fully, you shouldn't need the extension at all in normal use.

If the DeWalt's collet/shaft arrangements are the same as mine, there is a huge amount of depth below the collet normally, to accommodate cutters with longer shafts. So much so, that I keep drop-in lengths of dowel to act as depth stops for my commonly-used cutters (you get them out again by sucking on a bendy drinking straw!). I don't quite get the collet to rise above the table, but I can easily change almost all bits from above the table, as long as I'm careful not to catch any of the TCT with the edge of the collet spanner.