Issues With the Ohio Tool Plow Plane

I've had this Ohio Tool #96 plow plane for a number of years now and I really love using it.  So much so that I haven't used my Lee Valley plow plane since I fixed up the wooden plow.  But recently I worked on a project that required cutting a groove in the ENDS of a board, and the Ohio Tool plow was not up to the task.  It cuts great (usually) when going with the grain, but across end grain was not good.

Ohio Tool Co. #96

Left side view

My set of Ibbotson irons
From right, numbered #1 (1/8"), #2 (3/16"), etc. through #8 (5/8")

Probably 99% of the grooves I make are 1/8", 3/16" and 1/4".  The iron that inspired this post is the 3/16".  I'm trying to figure out why it's not performing as well as I would like.

To get a comparison, I pulled out (for the first time in several years) the Lee Valley plow plane to test it making an end grain groove.  It performed very nicely, with the groove having a smooth bottom and walls.

Nice clean groove in end grain - Lee Valley plow with 1/4" iron

So this had me take a close look at the wooden plow.  It wasn't that my irons weren't sharp - they were.  It just felt like the iron was not well supported well.  This hasn't seemed to affect the plane at all when grooving with the grain.  But with the extra resistance plowing end grain, the plane had a really hard time.  And this was true with a very light set.

I had a close look at the business end of the plane and the first thing I noticed was that there was a little gap between the wedge and the iron.

Showing the skate, iron and wedge

Pencil pointing to a small gap

That gap did not go all the way to the other side of the wedge and iron.  So there is good contact for the unseen part.  I trimmed the wedge a tiny bit to try to get a better fit, but didn't go far out of fear that I might ruin the overall fit of the wedge.

Looking further, I saw that there is not very good contact between the iron and the skate.  Most of you will know that the back of the iron has a V-shaped groove that fits on an inversely similar shape on the front of the rear skate.

Showing the V-grooves on the backs of the 1/8", 3/16" and 1/4" irons

This is where I don't have good contact

A piece of paper easily fits between 3/16" iron and skate

I was able to place that single thickness of paper about 3/8" - 1/2" up between the iron and skate.  This gave me an idea.  I stuffed a double thickness of paper between the iron and skate and trimmed it so that it wouldn't get in the way when I tried to plane a groove.

The double paper thickness went about 3/16" up between iron and skate

But it allowed me to plow a better groove in end grain

I decided then to look at the other irons.  I found the 1/8" iron fit well with the skate - no gap at all.  But the 1/4" iron also had a gap.  When I plowed a 1/4" groove with the grain, I could see the telltale sign that the iron is not supported well.

See the juddering lines in the bottom of the groove?

That means the iron is flexing and jumping as it's cutting - it's not well supported.  And while I was able to cut an end grain groove, it wasn't as smooth an operation as it could be.

1/4" groove in end grain

I ended up testing the 3/16" and 1/4" irons with a couple thicknesses of blue tape between the iron and skate.  I got much better cuts, but that is not a good permanent solution.  Somehow, I need to move the rear skate forward or get the iron to move back toward the skate.

If anybody out there has ideas of the best way to handle this situation, I'd love to hear them.  Please leave a comment.