Widening a Plane Mouth

[Jerry Thompson]

I have a SB #5 I rehabed. I added a Hock iron and chipbreaker. It produces fluff. However that is all it will do due to the thicker blade. I have moved the frog back as far as it will go and the blade will only peek out.
I am thinking of opening the mouth up or using the old iron/chipbreaker when I need it.
I have never done any work on a plane mouth. Is this explained in any book? I love the Hock setup and would like to keep it if I could open the mouth. Then again I don't want to ruin the plane. I is my first re-hab and I love using it.

[David Weaver]

take a machinists square, or any reasonably accurate square, and mark the mouth a fraction wider from both sides of the plane body (in case everything isn't as straight and square as you'd expect.

if all looks good, just file to your new line, it files easily.

Just do a little at a time, and to make it easy, color the cast with a red magic marker or something before you scribe your line into the casting.

[Joe Bailey]

If I may, I'd like to make a few points as a supplement to David's post.
Use a file with at least one safe edge, to avoid chewing up the ends of the mouth closest to the cheeks of the plane body.
At the risk of stating the obvious, you will be removing metal only from the wide edge of the mouth closest to the front knob.
As you do so, angle your file slightly, so that, rather than being perpendicular to the sole, the newly filed wall opens into the area inside the casting (15 degrees is plenty).

[James Taglienti]

If the cutter isnt resting on the plane body with the frog all the way back, you could instead take a round file and lengthen the two holes in the frog so it slides back more. Just make sure to go very easy if you file the mouth. I think
1/32 is more than enough.

[Jessica Pierce-LaRose]

Another point - the first time I had to do this, I figured, "well, it's all the way back, what more can I do?", but didn't realize (at least with the plane that I was working) thinking that I couldn't move the frog back past the point where it was co-planer with the mouth bit of the casting on my Bailey-style plane. Well, I had a little movement left - I moved the frog even further back - the frog's bed and the lip of the mouth on the base casting weren't co-planar, but because of the bevel on the thick blade, the iron still cleared this little protrusion. It got me the hair more room I needed.

[David Weaver]

Use a file with at least one safe edge

And if you don't have a file with a safe edge, just take a mill file and grind the edges off, or belt sand them off. I made several planes (out of tool steel) before I bought a proper file. I'd claim it was out of thrift, but the materials for one of the planes cost more than anything I had at the time other than a LN #8, so it wasn't exactly a thrifty activity.

[Jessica Pierce-LaRose]

David - what's your suggested method for grinding a safe edge on a file? Just use my bench grinder and care?

[David Weaver]

That's what I did, set the grinder around 90 degrees. It doesn't have to be that neat, it just needs to keep the sides and corners of the files from digging in. You could probably put tape on the edge of a file, too, and get away with that, but a safe edge file is nice to have.

If the edge of your file comes out gnarly, just get some 100 grit al-ox paper or something and put it on your bench and run the edge over it then.

A proper pillar file is nice to have, but they are expensive if you don't find NOS cheap somewhere.

[Trevor Walsh]

I agree with the safe edge, I did this to a noname 5 with a new blade as well. I prefer belt sander, but have also done it with a grinder. Safe edge files are very handy things.