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Adding cheeks to a Krenov-type plane





A year ago I bought a South African-made woodie on eBay ..

At 12 ½” long, I think that this would be termed a Junior Jack, essentially the equivalent of a Stanley #5 ¼.

This plane has been a bit of an enigma for me. I bought it because it held memories of my childhood (the story is here). However the construction of the plane is atypical of the era from which I would have liked it to come – the blade is held by a wedge, and the wedge is secured by a brass dowel – similar but not the same as the shaped cross-pin in a Krenov plane. The body is laminated and I think it is a recent, not a vintage creation.

Still, I really enjoyed using the plane. I set it up to fit between a full on wooden Jack (with a 8” radius cambered blade) and a smoother (with a fine cambered blade). It could take thick shavings, but not leave the surface with deep flutes to remove.

One down side was the blade. It was short, very short. Almost ground to the slot. Not that this was a problem with regards edge holding, but the short blade did make it difficult to adjust as the tote would lie above it and in the way of a hammer.

A kind friend gave me a new blade, a full length tapered Matherson, and I decided to use this. The Matherson required a lot of flattening, as well as removal of some of the metal from the sides as the original blade was 2 1/8” wide, an unusual width.

Here are the two blades ..



Installing the new blade meant that I had to modify the size of the mouth (a simple matter with a file) and the original wedge (which is when all the problems began). The blades-plus-cap irons are different thicknesses, with the new combination significantly so. The problem was not just reducing the wedge to fit, but that the holding angle changed with the new, thicker combination. The result was that the blade would become loose after a few strokes. The brass dowel had had a tendency to indent the wedge, and it would loosen after a while, but now the wedge loosened even quicker. A brass dowel is not a system I would choose.

The cap iron bolt also created problems – this made it more difficult to reduce the thickness of the wedge as the morticed slot needed to be deepened, then ran out of depth. The whole thing just became too much.

Time for a new arrangement.



Comment on blade holding methods

In my opinion there are several ways to hold a plane blade and these offer different levels of security. At the top of the ladder is a tapered blade held by a wedge into a cheek. At the very bottom of the ladder is a parallel blade held by a wedge into a dowel. They are used because they are easy to do this way.

A dowel is not the same as a Krenov cross-pin. Both may be laminated planes, but the cross-pin of the Krenov is shaped to hold a wedge. The area of a (round) dowel that registers with the wedge is perhaps a 1/32" wide, while the flat on a Krenov cross-pin is about 3/8" - 1/2" wide. The area in a cheek/groove is 2" - 3".



The Fix

This was an opportunity to improve the blade holding method by altering it to a more traditional set up, with the wedge being captured within grooves in the cheeks.

The fix is very simple – remove the bar (it slides out), then cut two hard triangles (I used Jarrah) to become the cheeks.

The design does differ from the traditional in that I have cut away the centre section. The reason is that this enables me to avoid the need to add a slot for the cap iron screwhead. I reason that the cap iron is better held by the sides alone, and this design frees the path to allows shavings to escape more easily.



Drill out the top of the curve, then use a fretsaw to remove the centre. Finish with rasps and sandpaper.



With the blade and wedge in place, I made a template out of paper. Test fit these, then mark and cut out the hardwood. Before installation, taper the lower section of the cheek (which will allow full shavings to escape). Then epoxy the new cheeks in place.

To finish, chamfer the top edges.





The finished plane …



The proof of the pudding … a few test cuts …

On a face.

On an edge



Regards from Perth

Derek



August 2010