Fettling Dado Planes

[Trevor Walsh]

Hello GG,

I'm having trouble with some Dado planes I've been attempting to get into full fighting shape. The blades are sharp (though not all have perfectly aligned irons, cuts deeper on one side) the knickers are sharp. However I'm having trouble cutting good dados, I get side walls that slope then bind, or become crooked. What steps should I take to diagnose the fettling that needs to be done, what do I need to make sure is right?

I can post some pictures if that's needed.

Thank you,
Trevor

[David Weaver]

What's a straight edge look like on the runner on the side?

Get the iron so that it's cutting evenly, that's likely the cause of it running deep. It's hard to manhandle a plane that's cutting a lot deeper on one side than the other.

A lot of the ones I've seen have a runner that's way out of straight as they get older, but I think the cutting deeper on one side than the other is the culprit.

Are you cutting them against a batten?

[Trevor Walsh]

Runner being the "skate" portion? And out of straight meaning the plane stock is bowed? I am cutting them against a batten. On the 7/8" dado the stock has shrunk quite a lot, and the knicker sticks out a lot from the non escapement side. I wondered it this caused some problems on the batten registration.

What should the knicker projection be?

[David Weaver]

nicker projection should be enough to score a line when you drag the plane backwards before you start a cut. too deep and it will hang up the plane.

Yes, in terms of the front and rear skate not being aligned because the body of the plane moves. Most of the ones I got (I poached 8 from some guy several years ago) are out one way or the other, some more than others, and like you're seeing, they've become noticeably narrower than the nicking iron.

I don't know if that creates that much problem or not, despite all of the dado planes, I still usually cut dadoes with a saw, chisel and router plane. I haven't even tuned most of the dado planes, and had no idea they'd be that whacked out when I ordered them, they looked good in pictures, but I think they are mostly from a later era in planemaking when stock selection wasn't done as well as it might have been on earlier planes.

The nicker being wider than the skate shouldn't be a problem as long as you keep consistent pressure against the batten and the plane stays upright.

[Jessica Pierce-LaRose]

The nicker or the iron being wider than the skate isn't a huge issue - being narrower would be an issue, for certain though. The iron of course needs to be at least as wider as the "skate", and make sure the iron is at least as wide as the nicker, or the nicker could be jamming in the groove cut by the nicker.

I bet Josh Clarke would have some ideas on dialing these in.

[Jessica Pierce-LaRose]

Make sure the iron is parallel to the stock, to. If the iron protrudes from the side more at the top of the stock than down by the cutting edge on one side, as the cut gets deeper, it'll push the plane to one side and make things bind. From the couple I've played with, it seemed there was a slight relief to the iron, so it tapered slightly as you moved away from the cutting edge. Same deal with the nicker (it sounds like you've got the kind with a second iron as nicker, not two blades) It's all the same mechanics as a moving fillester, just more complicated because you've got to worry about both sides of the thing.

[Trevor Walsh]

These are all good suggestions, I'll start working on them with this in mind. I had all 4 of them out sharpening at the same time, and may have been a bit rushed. I will attack these differently now. With only one plane out at a time I'll fettle it into working order before moving on. That should keep me from getting too excited and hastening through it.