I want to tidy up the bottom edge of a wooden door threshold.

I've never used a router but I thought it would be the perfect tool for this, running the router along the top edge of the door sill and cutting away rotten timber along the bottom edge. Sounds simple, I just have to buy the appropriate router bit. But after some fruitless searching I am at a loss to find the bit I need. I guess I need a slot cutter bit (to cut away the underside of the sill) with a shank mounted bearing (to run along the top edge of the sill).

I found template edge trim bits that look a bit like that (but the bearings are are all flush with the cutting edge) but was surprised that nothing off-the-shelf seems to be made (I could add a bearing and collar to the shank of a cutter bit but this does not seem to be recommended). All the guided cutter bits use an end bearing. I could use a guide fixed to the back edge of the step I suppose.

Is that the best solution or is a router the wrong tool for the job (there is no space for a circular saw etc though a multi-tool cutter could do it).


  • Welcome to WSE. Please consider that pictures and/or sketches help readers understand what you are attempting.
    – Ashlar
    Commented Jul 30, 2020 at 17:12
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    ... and for what it's worth, it's not clear to me from your question exactly what's getting cut. Commented Jul 30, 2020 at 23:23
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    I think that this question boils down to being a duplicate of this one: woodworking.stackexchange.com/questions/6356/… . I'm going to vote to close it but please don't take that to mean that you shouldn't have asked it. You just needed to understand terminology around these different kinds of bits to be able to ask it clearly. Commented Jul 31, 2020 at 16:01
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    Does this answer your question? What is the difference between flush trim, pattern, and template router bits? Commented Jul 31, 2020 at 16:01
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    Many thanks for your comments. Sorry for not posing the question well - trying not to appear too stupid. I have edited question and added pic. I guess it is more house maintenance than woodworking. I could not believe that from the multitude of router bits available I could not find the perfect one for the doing this job. My guess is that running the router freehand with a slot cutter bit is all that is needed.
    – mkc
    Commented Aug 1, 2020 at 6:26

1 Answer 1


If this was my job, I wouldn't walk out to the garage and steal the bearing and lockring from a template bit. (The biggest issue is that the shank on any normal rabbeting bit isn't long enough to reach where you want while keeping the collet off the existing wood.)

I'd consider cutting the top surface clean off (at the line of the door would make sense), then attaching a replacement bit of nosing (glue/screw). That could be done with a combination of a circular saw plus multitool/chisel. (If you want an excuse to buy a router, then use a straight cutter with a guide that the base rides against.) If your cut is imperfect, use a void filling glue like an epoxy. If you want to be fancy, put a drip kerf on the replacement nosing. This exercise will also tell you if the threshold is rotten through and through and in need of complete replacement.

To specifically address your comment about a freehand slot cutting bit, that would work, but only if the shank was really long. Otherwise, you won't have enough of the shank seated in the collet and that can go very bad very quick.

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    Thanks for your answer. Was it that obvious I was looking for an excuse to get a router?
    – mkc
    Commented Aug 2, 2020 at 13:59
  • @mkc see, I knew it was an XY Problem. You were looking to justify a router purchase, not fix this sill!!! :) Welcome to the club! ;)
    – FreeMan
    Commented Aug 2, 2020 at 16:26

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