The Ruler Trick For Router Planes

I picked up a record 722 small router plane a while back. Its a nice little router with a 1/4 inch cutter, which it holds solid as a rock. For most jobs, I use a full size router plane. The small router comes into its own when you need to reference off very thin stock. The small base makes life a lot easier. Knowing I had just that kind of job coming up, I set about sharpening my 722, as I attempted to flatten the bottom of the iron, I discovered it was in very bad shape. There was a huge belly in the bottom of the Iron. I worked it for a long time on a coarse diamond stone, and made little discernible progress. The small flat on the iron makes it challenging not to simply rock the iron around as you lap and preserve the belly. Then I remembered! The ruler trick is not just for bench planes! Read on below to see how it worked out for this small router plane.

The Record 722, compact, affordable and reliable.

This is where we started out, a little hard to make out, as its been a while since I initially tried to lap the bottom of this iron, but there is a large belly in the middle, and lapping has gotten me no closer to the edges.

This is my setup for the ruler trick. Part of the trick is , use the same ruler every time! This ruler lives with my sharpening stones. It is its only job. Put a little of the heel of the router plane iron on the ruler, I apply pressure to the front of the iron, and work it side to side along the rule. This is a 3000 grit diamond stone.

After about 30 seconds on the 3000 grit stone I had a flat at the tip of the iron along the belly, another 30 seconds showed no progress. Oh well, time to drop a grit.

We move on to a 1200 grit diamond plate.

We get pretty rapid progress, after 3 30 second bursts of lapping, it too slows down , and progress toward the edge on the right is not really happening.

Out comes the 600 grit diamond plate. 30 seconds here and we hit the far side of the edge. Its not very far down, but if it was a flatter iron and I only had a polished hair line all the way across I would be happy.

I have already polished the bevel of the iron, so it back to the 3000 grit plate for just a few sidewise swipes to remove the burr from lapping.

I can now shave a bald patch on my arm with the iron. That is far sharper than a router plane iron generally needs to be (no harm though).

The moment of truth, lets take it to wood.

It is slicing cleanly with little effort

And leaving a very nice surface behind.

I sometimes do and sometimes don’t use the ruler trick on bench plane irons. I prefer not to for purely aesthetic reasons, but on a really beat up iron it just saves so much time. The small back bevel it creates makes very little difference to a router plane iron, and does not seem to interfere with clearance angles at all. This saved me what probably would have been several monotonous hours, if not building some sort of custom jig to hold it flat. Just remember, never use the ruler trick on your chisels!