Over the past couple of years the Oval Bolstered Mortice Chisel (OBMC), aka “pig sticker”, has made something of a return to favour. In part this has been due to the word-of-mouth recommendations, and in part discussion on the various forums. They have even begun to be manufactured once again by Ray Iles.
Ray
Iles
For most, unless one has access to flea markets, the easiest method to obtain these chisels is via eBay. The better quality chisels are now expensive as they have become the target for many. For much less money it is possible to pick up unhandled chisels or chisels with damaged handles. Many tend to avoid these chisels as the perception is that rehandling an OBMC is a difficult task, one for the expert. Well, the purpose of this pictorial essay is to illustrate this process and demonstrate that it is really quite easy. Perhaps this will make these chisels more affordable to those interested.
The main features of the OBMC include:
A blade that tapers very slightly from back to front.
An oval bolster that supports the handle. My understanding is that a leather washer is not used between the two surfaces (although sometimes this is found).
A triangular, tapering tang.
The bevel is traditionally ground at 20° to aid penetration, and the edge then gains a 30-35° microbevel for strength.
The junction between the bevel and the blade front is rounded slightly to permit easier levering of chips.
I have rehandled several of these chisels to date. These include the three on the left (below). The wood used here was Grey Gum (tinted with a Jarrah stain), Jarrah, Beech, Ripple Ash, and Rosewood. Rehandling the OBMC in a variety of woods seems to be a little fun and certainly is preferred to rather bland Beech, which is more traditional.
There are a few methods of attaching handles. One involves boring a wide, straight hole and gluing in the tang with epoxy resin. This should work, but it is not traditional. Another method is to roughly form a recess, then heat the tang red hot and allow it to burn the remainder of its hole. I am not mad about this method as a charred internal surface does not sound to me to have much strength. My own preference is to form a precise recess for the tang, leaving just a little room to force the tang in so that it has a tight fit.
Here is the target chisel. It is a ½” by Ward, in excellent condition and a near-full length blade of 7 ½”. The tang is by far the largest I have seen or worked with to date, which will be more of a test than the average, smaller tang (see at end for comparison).
We begin with choosing a suitable block of wood for the handle. I am using Grey Gum, partly because it is hard – damn hard, even by Australian standards (see table below) – but also because I have several roofing rafters worth that were given to me free.
How hard is hard?
Mark the center and drill a pilot hole the total length of the tang.
Note the dimensions of the tang at the top (at the bolster end) and ½” from the bottom. Transfer these to the block.
Drill again, this time the thickness of the drill bit should be the same thickness of the tang at the point ½” from the end. Then drill ½” deep the width of the tang as measured at the top.
For narrow tangs and softer wood than this Grey Gum it is possible to do the next step with a standard twist drill bit in a power drill. Since I have a wide tang and hard wood I am using a drill bit that saws.
The aim here is to drill straight down, then pull the drill bit across and thereby triangulate the hole. Here I have done this twice, creating a cross.
Other tools that will soon be used are chisels, ideally narrow sash mortice types.
Using the drill bit and sash mortice chisels, square of the elongated pyramid-shaped hole. It is important the sides are square to prevent the tang twisting.
Pare a little more until the fit is good. You want to aim for a firm hand fit with about 1/8” – ½” showing. The amount of leeway depends on the hardness of the wood – softer, more elastic wood can tolerate more leeway, darker, denser wood tolerates less and is at risk to split with undue force.
A couple of thumps on the bench top should drive the tang full length.
Draw a centerline from the end of the blade through the handle block.
Repeat this all the way around.
And add further lines for the ends of the bolster.
There are several ways to remove the waste – spokeshave, drawknife or, as I did here, a handplane.
One can take thickish shavings with, say, a #3 ……
… or use a scrub plane.
Keep in mind that the oval tapers toward the bolster.
Smooth off the surface with a spokeshave. The HNT Gordon (pictured below) was especially useful as its high cutting angle permitted it to shave into the grain without tearout. The other spokeshaves here, a Stanley #53 and a Stanley #55, are both excellent users but were not as successful with the Grey Gum.
The oval end of the handle is marked with a squeeze on a roll of insulation tape.
A little sandpaper or a card scraper to smooth out the surface. Then a coat or two of Boiled Linseed Oil (BLO) and another of wax … and …
… ta da …. The final product ... well, almost – just a little rounding off of the end to be done.
Another view …
The final version with rounded end.
The size of this ½” chisel is better illustrated when against a 3/8” version (the same as in an earlier picture).
I hope this has been helpful and get a few more OBM chisels back on the road.
Regards from Perth
Derek Cohen
December 2006