Hacksaw Knife No.2

A bi-metal hacksaw blade has the potential to to make a thin scalpel-like blade. The cutting edge of a bi-metal hacksaw is made from HSS (high-speed steel) which gives it great cutting strength and durability but to make the whole blade of brittle HSS would be costly and vulnerable when flexed so a few millimetres is electron-beam-fused with softer but more flexible spring steel. The flexible spring-steel backing supports the brittle HSS so that it cannot flex enough for cracks to propagate and snap it.

The blade I used is the Bahco 3906 24 TPI Sandflex and has a black coating followed by the distinctive orange paint and deep blue printing.

 I removed most of the orange with paint stripper but the black coating was tougher and I used wet-and-dry paper for this. One could argue that it would have been better to keep this protective surface but it didn't look that great.

With the majority of the blade being softer (though not soft) steel it could be cut with another hacksaw blade and shaped with a file. The teeth of the blade were sharpened with diamond stones. To maximise the HSS remaining behind the edge,  I removed as as possible. I used a round file to create a semicircular sharpening choil just before the point at which the blade goes into the handle. This choil ensures that the full extent of the edge can be sharpened.

The bare steel was given a light patination by suspending the degreased blade in a container of a warm salt-and-vinegar solution so that the blade sits in the vapour not the solution. This led to an attractive mottled-grey patina that should give some protection against corrosion.

The handle was made from pieces of jarrah given to me by my brother-in-law who lives in Australia. From his work in overhead electricity distribution he had access to the jarrah crossarms from that were being replaced. I love the provenance of these and the idea that they had been outside in who-knows-where in Australia in all weathe4rs