I'm looking for a tool to smooth/flatten down a surface in a rectangular channel in the center of a piece of wood (I constructed the piece by gluing two halves together, but stupidly didn't clean the channel halves well prior to gluing). The channel measures ~1" wide x 2" long x 8" deep (you can think of it as an 8" deep mortise). It's roughly square, but needs a lot of help. Only one surface actually needs to be flat/smooth.

The best tool that comes to mind for the job is a file or rasp, but I need the handle offset so that it can actually get in the channel (the piece's construction is such that without an offset handle I wouldn't be able to put the face of the tool against the surface of the wood). Alternatively if there were a way for me to sand inside the channel that would work too, but I'm unfamiliar with any way to get sand paper in a channel that deep/narrow.

After a ton of searching for things like "crank necked rasp" and "offset handle file" I finally learned that there is a name for what I think is my dream tool: straight ironing rasp. This, for example, looks great:

enter image description here

It's pretty pricey and ships from Europe. There seem to be tons of curved ironing rasps available from many of the usual online stores in the US, but very few straight options. So far this is the only one I'm able to find. This link implies that Auriou used to make a straight one, but now I can't seem to find it anywhere. Am I missing something here? Why are there so few of these tools? Does it go by a more common name that I'm just unaware of?

  • I wonder if I have a preconception wrong here. My answer works either way but this recess is now enclosed after gluing? So its more like a mortise now? Or is it exposed enough that you could use a router like Graphus suggests?
    – Matt
    Commented Oct 8, 2015 at 12:42
  • @Matt shoot I should have explained this better. Yes you can think of it as an 8" deep mortise that's 1"x2" in the cross sectional area. I need just one face of that mortise flattened/smoothed.
    – Doov
    Commented Oct 8, 2015 at 17:32
  • 1
    Pictures always help
    – Matt
    Commented Oct 8, 2015 at 17:33
  • @Matt -- definitely. I will try to take one when I'm back home with the work piece. Should have included it in the original post.
    – Doov
    Commented Oct 8, 2015 at 17:39
  • Obviously this would have been easier before you glued it together... Hindsight is always 20:20, right?
    – keshlam
    Commented Oct 9, 2015 at 0:48

5 Answers 5


It's roughly square, but needs a lot of help.

Paring Chisel

My first thought for this was a paring chisel. Especially if one of the surfaces needs to be flat and smooth. Paring chisels are designed for clean long cuts and are not meant to be struck. Instead you could stand over the channel an push the chisel down with your body weight. The tools length would help keep the channel square.

If your recess is actually 1 inch wide then using a 1 inch paring chisel would be the best choice. Those chisels are designed with length in mind so finding one that is at least 8 inches long shouldn't be too hard.

If you have never used one before test on another piece. These are not inherently hard to use but the ease of work can depend on your wood species.

Paring Chisels

Image from WkFineTools

The rasp blade you have picture would not make for a smooth surface. If it was like a cabinet rasp that would be better. Much like Graphus I have not seen handles rasps with necks like that.

Given that my presumption was partial wrong about the work piece I can offer another suggestion. Perhaps a swan neck mortise chisel? Really depends on the angle you need. One primary purpose is to clean the bottom of mortises but the curved head might still be useful. I think it would be harder for this one to get a clean surface but if you are careful it could still work. I have an even better suggestion after that though.....

Cranked neck paring chisel

Even better though is I found that they make cranked neck paring chisels as well. They can also be called cranked shaft paring chisels.

Cranked neck paring chisel

Image from woodworkingshows

  • When doing this type of work with a paring chisel, put the bevel side down. I think there's a natural tendency to do it the other way.
    – popdan
    Commented Oct 8, 2015 at 12:03
  • @popdan That does seem strange to me and will have to look that up. I have always seen Roy Underhill pare down bevel up. In this case I don't think that is an option though since I understand that the recess is enclosed so I don't think you can get the edge down when you get deep into the recess.
    – Matt
    Commented Oct 8, 2015 at 12:41
  • You're not going to remove a lot of material this way, it's mostly a way to create the flat bottom of a mortise or similar.
    – popdan
    Commented Oct 8, 2015 at 13:05
  • 1
    @popdan Of course. From the OP description I don't think we need to remove a lot of material. Just need to clean it up. Else the answer could be a mortising chisel but a paring seems a good fit from my understanding.
    – Matt
    Commented Oct 8, 2015 at 13:51
  • 1
    @Doov Found out they do make crank neck paring chisels. Not sure about availability or cost.
    – Matt
    Commented Oct 8, 2015 at 18:35

Yeah, files/rasps with offset handles are very specialised. I don't think I've seen one in the wild ever; I know of them only from old books and from tool catalogues.

You can in theory form your own cranked-handle file or rasp from a standard one. It requires a relatively minor job of annealing and bending at the tang end, but there is some risk of losing temper near the business end of the tool so I'd be hesitant to try it unless I had no other choice.

I think that the best solution here is a type of hand router. You can buy a number of types and there are a few basic types that can be made in the shop, but the chisel router AKA "poor man's router" might be just the ticket since they're so simple: you just need a piece of wood (and even pine will do), a chisel and a suitable drill bit to make one.

Poor man's router

More detail given in the YouTube video the above image is taken from.

  • I might be wrong but would this not work since the recess is now enclosed according to the op?
    – Matt
    Commented Oct 8, 2015 at 12:36
  • @Graphus thanks for the tip. Unfortunately I don't think this will work for my piece. I should have clarified this, but the channel is 8" deep
    – Doov
    Commented Oct 8, 2015 at 17:34

A simple, effective and less expensive option would be to glue various grits of sandpaper to appropriately shaped wood blocks. If you need off set as in the case of the crank neck chisel, a handle could easily be fashioned from a variety of materials and attached. Another way would be to make the tool from a single piece of wood, appropriately shaped with a flat for the sandpaper and curving up into a handle.

It's completely customizable and readily available. No fussing with the wait time and expense of a tool you are likely to use very rarely.


I'm looking for a tool to smooth/flatten down a surface in a rectangular channel in the center of a piece of wood

You might consider using a planemaker's float:


but I need the handle offset so that it can actually get in the channel

Or, if you need the swan neck on the tool, a face float would work too:

face float

These are similar to files, but the teeth are much larger and triangular-shaped (similar to what a saw would look like if it was much thicker).

Planemaker's floats were traditionally used by wooden plane makers to flatten the part of the plane where the iron beds and to flatten other parts of the plane a regular chisel couldn't.

Face floats are useful for cleaning up tenon cheeks. They would be suitable for your use given the needs you stated in your Question.

The couple of links I provided were for Lie-Nielsen versions of these products - and they come with a pretty hefty price tag (as to most LN tools). However, it is simple enough to make these yourself if you have access to tool steel, triangular files, a means to heat/harden/temper steel, and patience. The heat treatment may be unnecessary according to some people, but it will make the edges last longer. The nice thing about making them yourself is you can make them as long as you need.


Why are there so few of these tools?

I assume for the general capitalist pig-dog reason - no/little demand. If you haven't noticed, machine-made rasps these days leave a lot to be desired. Companies like Auriou and Liogier are the only ones I know of that do hand-stitched rasps, and every review I've read is that they cut like a dream compared to machine-made rasps. With the overhead that goes into tooling for making the different tools, having special tooling for a rasp that rarely gets bought (I assume your ironing rasp falls into this category) makes no economic sense.

  • I have one of these and just thought it was another rasp. Cool
    – Matt
    Commented Oct 8, 2015 at 16:12
  • Thanks a lot for the info, @grfazee. That float looks like exactly the tool I need, but it's slightly too wide. Your answer re rarity of the tools makes a lot of sense. I'm pretty new to woodworking so I have only used machine made rasps a few times (only realized there were hand stitched ones while exploring this topic), but I was surprised at how poorly they seem to cut (or maybe better put at how inefficient they have been compared to what I anticipated).
    – Doov
    Commented Oct 8, 2015 at 20:47
  • Since machine-made teeth on rasps are so regular, they tend to fall into each other and create patterns on the surface you're working. Hand-stitched ones don't have this regular pattern, so the surface is more even and they cut much better.
    – grfrazee
    Commented Oct 8, 2015 at 21:57

Another option:

Crank Neck Flat Bastard File

Not unlike the rasp you found, but not pricey, can be ordered domestically, and probably produces a smoother surface.

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