Monday, December 21, 2015

KN18 THROUGH TANG - INITIAL LAYOUT

With the holiday season coming there are orders to fill and knives for the kitchen are in demand. The KN18 pattern is a full tang, but I have modified it on steel to create a through tang. The stock is 3/32" x 1-1/2" AEB-L, which will make a good slicer.

 Here I have the pattern in thin plywood.
To make a through tang, the pattern is traced and modified. You can see the full tang blade and how I will be extending it about an inch. 
 Cutting out the basic shape on the band saw.
The tang has to be tapered, but the end needs enough meat to hold a machine screw for the butt cap.
 Now over to the belt grinder to bring the shape to the lines.
Here you can see how the stainless steel screw will  fit into the end of the tang. The needs to be removable or the bolster end would have to have larger hole in it to pass over the screw head.

KN18 THROUGH TANG - HEAT TREAT AND GRINDING

Here is the blade coated with Condursal. This protects the blade during heat treatment. The blade gets to over 1000°C.
Straight out of the oven and into the oil.

After two tempering cycles at 185°C (365°F) I start the bevel grinding. The steel is very hard and I cannot overheat it now or it will be ruined.
This grinding takes about an hour.
More grinding. Once the edge is down to about 0.02" I move to a finer belt.
Now the edge is at 0.015" I start the scotch-brite conditioning belt. This give a brushed look.

KN18 THROUGH TANG - STACKING THE HANDLE

With the blade done, I start on the pieces to make the handle stack. The front end or guard is a piece of AEB-L left over from cutting the knife profile. I make a slot in the guard by drilling four 5/64" holes and joining them with a needle file. Lots of patience and test fitting against the tang is required. This picture is taken when test fitting.
For the main part of the handle I have a block of Amboyna burl that has been stabilized. Ideal for a kitchen knife.
Some African blackwood will make another part of the stack. The holes here are not super critical as they are out of view. I also cut two pieces of red spacer material.
The tang has to be checked with the screw in place. The screw cannot turn under moderate torque.
Now that the block is sized, I drill it out to fit the tang. Three 3/16" holes go in about 1/2 way. Then they are joined to make a slot. I then drill a hole from the other end to let the screw pass through.
A test fit showing the front parts and the screw sticking out.
A piece of 3/8" stainless 304 is drilled and tapped to 8-32 to match the tang screw.
Here you can see how these are lining up.
Ready to mix some G/flex. For this build I mixed 10ml (2 tbsp).
Here's all the components lined up.
On with the gooping. The epoxy goes between all the pieces and lots in the main block hole.
Then I screw the stainless butt on and compress the stack. Only about 5 to 10 lbs of force is needed. Not too much or all the epoxy will squeeze out.








This is a graphic I made to show the basic handle construction concept.

KN18 THROUGH TANG - SHAPING THE HANDLE

After a day of sitting in a warm place, the epoxy is hard enough to grind. I am starting with a 36 grit zirconia belt with the flat platen.
The objective is to true up all four sides and make clean rectangles.
I want the slant back, but I cannot go too far. If I grind through, it will expose the threaded hole that the tang screw is in.
I used the water bucket here a lot. The epoxy is good, but no epoxy can stand the heat that will build up in a chunk of steel being ground down.
I start to round the handle by holding it at 45° and passing across the belt. Occasionally, I work the handle in the vertical position.
At this point I am checking the symmetry and working equally to make a nice oval cross section. I am dipping the handle in water just about every pass to keep it cool. If you expose the screw hole in the butt, you can plug it with a piece of brass like I did. ;-)
Here the handle is starting to feel good in hand.







Moving up to a 220 grit AO belt in the slack belt mode. I find this slightly burns the wood and darkens the burl considerably.
Here you can see the profile of the handle and how it will be in it's finished shape.


 

KN18 THROUGH TANG - FINISHING UP

 A few last things to do. Etching the marks on the blade. Setting the edge.

And honing the edge on the water stones and strop.