I constructed these jacks after studying two pairs I had the use of occasionally. One by Dino Tedeschi and the other by Ivan Smith. In time I may make others and take photos during their construction.
The overall length is 430mm with the blades being 225mm. The blades were fashoned from 15mm x 4mm AISI type O1 tool steel. The shaping was done initially with an angle grinder and grinding disc, later switching to a flap wheel for a less agressive action. Final shaping was completed with a file. The back was formed from 38mm wide 1.6mm CS70 spring steel using tooling similar to that shown in the pacioffis page. The blades were brazed onto the back and the back was then bent round. At this point I hardened the blades by heating them to about 800°C and quenching in oil. Tempering was done by heating the jacks to 290°C in my top loading kiln. I do not know if the Dino Tedeschi or Ivan Smith jacks had hardened blades as I didn't want to ask to test them but it should lead to a longer life before resharpening.
A useful offshoot of making the tooling to form the backs is the variety of tools which can now be made. This set of crimps in stainless steel as a example. A set with carbon faces to minimise chill marks is planned.
A bit of a challenge making round tapered blades for jacks as I don't have a taper turning attachment and didn't have a travelling steady at the time. After consideration I produced the jig shown.
The brass guide has a semi-circular groove to support the steel rod. The rod shown is Ø1/4" (6.35mm) and is quite flexible allowing it to be bent forward by the guide. This results in a long taper being formed when a cut is taken.
The cut is taken to produce the tapered blade in one pass as after turning the taper the guide will no longer support the tapered section.
The finished jacks. So far these have proved particularly nice to use for the stems of stemware.