In this article, I thought I’d go over my assessment the method commonly known as the “Ruler Trick” used to create a smooth face to the iron, is attributed to David Charlesworth, a well-known North Devon furniture maker.
This method has its place when users are faced with creating a smooth flat area on the face of the iron when imperfections are present by using a slim ruler to raise the rear of the iron slightly, this creates an angle so the leading edge of the face can be worked along a flat abrasive surface.
Creating an angle on the iron face increases the iron’s leading edge angle so where most bench planes are 45 degrees it would be possible to change the degree to 50 degrees by bevelling it 5% which would change it to what is known as a York pitch, this angle was used predominantly for difficult grains and can be found in occasional antique planes. It’s always better to find an old plane that has this York pitch but a leading bevel on the face of the iron would work in the same way.
It’s also important to point out that although this ruler trick method works it should never be applied to paring chisels because it will cause them to travel away from the desired line of travel within a cut.
So basically if your iron is in poor condition, ie. pitted, this method has its merits. Still, from what I have found from planes using this method it gradually creates a longer front bevel in time which makes it hard work to correct it back and flatten iron again without grinding a lot of the length.
Also because you can’t use this method on flat chisel faces that have to be flattened properly, is it reasonable to ask why you would make exceptions for a plane iron?
Is it a practice I’d endorse? The simple answer is No unless I had a pitted iron and specifically wanted to change the face pitch. From the thousands of used planes I have had through my hands, it is very apparent how few have seen a real flat surface which is needed when a chipbreaker is part of the setup.
Norris Planes when new added a note, explaining they had set up and refined the plane but were not responsible if users altered this refinement by poor maintenance. I believe this note was due to the fact when a plane blade and chip breaker have been fettled in with two perfectly Parallel flat surfaces it gets altered by working the back of the iron or mishandling or altering the chip breaker.
Likewise, at Tooltique, we make sure the faces are properly flattened and any imperfections are removed so this ruler trick method isn’t needed. Once a plane iron face is perfectly flat it should not be worked again on an abrasive surface, there is no need. We also flatten chisel faces and remove any imperfections, it’s the only way to get a perfect refined edge that will hold for longer.
Honing and Deburing: In our workshop, I use a fine Indian stone, a natural fine slate stone, and a leather strop with a polishing compound to hone the edge and the only thing that touches the flat face surface is the strop when deburing. This practice retains the flatness and ensures you won’t change the refined fettled flat area.
Remember you only have to flatten any face once, it’s worth doing it properly but if you don’t want to do this work because it can take a lot of time and effort, we are naturally a solution because our planes have had this work done.
Note: I do not use diamond plates to flatten irons because I’ve found they aren’t perfectly flat, they also wear far too quickly even though there are better makers of these products and yes I’ve tried them all. To flatten an iron use 10mm (min) Float glass (on a flat surface, supported in any shallows) with an adhesive-backed abrasive is what I would recommend.
Every good workshop should have a piece of float glass, and if you have got a diamond plate use it to soften the glass edges.
