We don't have any secrets at Tharwa Valley Forge and are very excited to be able to share all that we have learned about knives and bladesmithing. In addition to being the largest knife-making school in the world, we employ the largest number of full-time bladesmiths in Australia, so we've got a large base of knowledge to share with you.
Asides from their highly specialised cutting geometry, Japanese kitchen knives are also notable for their distinctive handles. Home cooks frequently overlook the mechanics and ergonomics of knife handles, neglecting an element that factors into the performance of a knife as much as the shape, size, and grind of the blade.
Almost all professionals prefer carbon steel blades because they have the sharpest edges, stay sharp for far longer, and are easier to sharpen than stainless steel blades. With a modicum of knowledge and a minimal amount of care you too can enjoy the superior performance of carbon steel blades whilst getting a literal lifetime of service out of your knives.
I was making a large kitchen knife for a client, when I realised that it wasn't going to fit in my knife vices to shape the handle. So I made a new holder that bolts onto the existing bracket just for this one. It is a monster - 75 x 25 x 350mm. Enough for the biggest of blades. It needed three screws to squeeze the blade tight.
A nice feature of the Knife Vice Mark II design is you can have different sized clamps that fits different blade. Easy to swap in and out as required.
When hardening blades, especially large ones, warpage can sometimes occur. The choice of steel can minimise the risk, as can a good normalising cycle, but sometimes it just happens.There are a number of different ways to try and fix the bend, not all of them are guarenteed.
One gentle way is to use a Japanese straightening stick or "Magebo". I found this in Murray Carter's excellent book "Bladesmithing with Murray Carter". It is made with a large piece of hardwood, by cutting a slot or to (just thicker than the blade thickness) and making a handle. The bent blade is first tempered, then the back softened. This is to reduce the risk of breaking. The blade is then placed in the slot, where the bend is, and some gentle pressure applied to torque it straight. Gently does it.
It possiby could be used straight after quenching when still hot, I'll have to try it. I dont normally expect my blades to warp, but should have the Magebo hanging up near when I heat treat for emergencies.
I asked John Price from Radiusmaster what he recommends for belt grits in grinding a knife. His tip was to use a sequence of belt grits 60, 150, A45 then A6 to take it to almost a hand rubbed finish level. This is the smallest number of belt changes he recommends.
A good quality 60 will remove stock without putting too many scratches in. The 150 will clean out the 60 scratches before leaving an even finish. The A45 and A6 Trizac belts put the final touches on. The blade can be quickly hand sanded with 500 wet and dry for a satin finish, or higher grits before being buffed for a mirror polish.
Cutting a slot for a tang in thin metal can be a fiddly experience. When trying to drill a series of holes it is hard to hold down the small thin pieces of metal. Sometimes the drill bit grabs shim and it spins up damaging the it. Milling the slot has similar issues. I have been wrestling with a effective solution for years.
Lately I found a 1 ton hand punch on eBay for $30 that makes quick work of the job. It is like a leather punch on steroids. It can punch different sizes holes in thin brass, spacer material or leather with little effort. It is safe and quick to use and doesn't bend the shims. It comes with seven different sized punches.
One of the challenges in forge welding is preventing the surfaces that you want to weld together from oxidising when heating. If they do oxidise, then the weld can have inclusions or gaps, which can open up later. A flux is used to stop this surface oxidation, or to dissolve it. For years I had used Borax to prevent this. When the pieces were heated, the Borax powder was sprinkled all over the surfaces, allowed to melt, then the pieces were hammered together. The problem with Borax is that it is highly corrosive when liquid, especially bad for the forge lining. Borax can easily eat through the lining in a session. To prevent this, I filled the bottom half of the forge with some sacrificial kitty litter (the clay type), which mostly caught the Borax. This didn't protect the sides though.
A new method of fluxing is to use Kerosene. By soaking the pieces in Kerosene before heating, you coat the surfaces in the oily liquid. When the steel is put into the forge, the Kerosene burns off, leaving a layer of carbon coating the surface, which inhibits oxidisation. The advantages is that Kerosene can get into cracks and doesn't harm the forge lining. This will not work with already oxidised surfaces, they need to be clean to start with. Borax would still needed to dissolve the scale. But using Kerosene to start with, greatly improved the success of your first welds and limits the need of Borax.
Safety note: make sure you have the Kerosene in a fireproof container, with a lid. Don't put red hot pieces of steel in the Kerosene. Although it doesnt explode, it can flare up. And the fumes aren't too good for you either,