Stamping is a process of cutting out a saw blade from a sheet of high carbon steel.
In order to minimize distortion and burr which affects different processes later on, we use our special original die.
The way die is manufactured greatly influences the productivity of the production of the blade. We came up with the special die to make as much blade out of the metal sheet as possible.
We use high carbon steel for our saw blade.
We use carbon tool steel which is generally called SK steel.
Carbon tool steel we use has hardness Hv500 to Hv650, and they are five times as hard as a regular steel.
It is difficult to stamp out SK steel which has hardness five times more than that of steel since it causes friction. Thus it's more common to cut steel into the shape of blade using laser.
By laser cutting, cutting edge hardens, and it affects some processes later on. That's why we use stamping.
Steel which is wrapped in the shape of a coil is curled. By uncurling and straightening the steel before stamping, we can make make flat blades.
It's a process of grinding the blade into the shape of the teeth.
This is an extremely important part in saw manufacturing process since it influences the product quality.
Originally, saw manufacturers used diamond shaped file to make teeth on a hand saw. Now for saws with replaceable blade, borazon wheel whetstone is used instead.
If there is a variation in the size of each tooth, it has a negative influence on the tooth setting processes and it affects the quality of the blade. Smaller teeth is weak, and the saw tends to move towards bigger teeth, so it is hard to make clean straight cut.
We can control the size of the teeth by a fraction of a thousand with our automatic machine. We control the quality of our products by a fraction of a hundred.
Our machine can run 24hours a day.
By just a single chucking, the blade is firmly secured on the machine. This greatly improves the product quality.
SK steel easily gets rusty, so if you leave it outside for even half day, it becomes slightly rusty. If the saw gets rusty, the teeth becomes dull and the rust sticks onto the cutting surface.
We make all our saws go through special surface treatment.
We can make plating evenly on the surface, and nickel plating film coats the surface and makes the blade stronger against rusting.
This special nickel plating becomes a great advantage especially in coastal areas.
With electroplating, coating is thicker on the edge and thinner on the flat surface. Whereas with electroless plating, the blade is evenly coated with the film even on the edge, so even with extra thin coating, it greatly improves resistance to corrosion.
These blades were left outside in the rain and wind for a week.
The blade on the bottom is with our electroless nickel plating. You can see rust on the blade without plating, but you cannot see rust on the blade with plating.
These blades were left outside in the rain and wind for a month.
The non-plated blade is completely covered in rust, but the blade with plating only has some rusty parts.
After stamping, blade is not completely flat. There are some warp on the blade.
We take away warp by using roller.
First one is removing warp that's caused by stamping.
The second one is for removing warp which was caused by making teeth.
Warp is removed by making scratches on the back of the blade. These tiny scratches stretches the surface.
The roller removes warp based on different thickness and shape of the blade.
The roller leaves scratches in two rows. The special hard steel is used.
The final inspection is done by visual obserbation by an experienced worker.
The tip of each tooth is set to the left and right.
If the teeth have no sets, wood dust gets stuck in between each tooth, and it prevents smooth cutting. If the setting is too much, it's harder to control and use the saw.
If the setting is unbalanced on each side, the saw tends to move towards the side with the bigger setting angle.
The blacksmith used to make setting on the teeth by hand. The teeth setting machine was designed based on how it was done by hand, but since setting process is done on a single blade at a time, the setting on each blade was uneven. We currently use a machine that make setting on one side at the same time and the other side also at the same time.
Our special automatic teeth setting machine has a special system in which it adjusts its setting for making teeth with best sets.
Tapered blade was common for pruning saws. However, our technique with high quality set teeth are now applied on pruning saws on green wood.
It is processing to cut the tip of each teeth diagonally.
If the height of the teeth is not even, the saw tends to move towards the side with the longer teeth.
Since saws carves the material it's cutting, sawdust is produced.
If the height of each teeth is even, sawdust remains on the cutting surface, and it prevents smooth cutting. Taking out sawdust from the cutting surface is actually more important than the sharpness.
We can control the accuracy up to a fraction of a thousand. We control our product quality by a fraction of a hundred.
The machine can run 24hours a day.
Small difference in the raw material and slight variation in the setting of the machine causes small variation.
Edge making machine has a special control system so that it can apply ideal method for different types of blades.
To have hand saws that give you smooth and straight cut, teeth, teeth settings, and teeth edges must all be perfect.
We use a projector at all steps and try to attain accuracy up to a fraction of a hundred.
After grinding, blades are washed. After they are cleaned, blades are finally ready for laser marking.
Laser marking is done by carving marks on the surface of the blade. Marks do not dissappear even if they're washed or rubbed.
Electroless nickel plating is done on the surface of the saw blade.
Marking is possible with also having the characteristic of rust proof since the plating film is about 2um, and the laser engraving is 1um.
I minimize the distortion to the saw blade by the marking.
Our company logo, made in Japan, product name, thickness, size, and item number are marked on our blades.
Since item number of the spare blade is marked on the blade, it's easier to know which blade to purchase.
Since the same format is used to mark different types of blades, it's easy to see the product name and spare blades.
It's a process to check the quality of the finished product.
We strictly control the quality of our blades.
We randomly pick one blade out of a couple of dozens and use a projector that projects an image 20 times the original size to check the quality of the teeth settings.
The projector is also used in other processes to check the shape of the blade.
The projector has a device that can measure the size of different parts of the blade.
We check the number obtained by these measuring devices and see if they meet our standard.
Meeting the starndard number doesn't mean that the sharpness is the same for all blades.
We randomly pick one piece and check the quality of cutting edge by actually cutting wood.
For our Dozuki extra fine saws, we check all the pieces since even a slight difference influence the cutting edge.
We check all the blades with image processing.
By image processing inspection, size of the blade is double checked and it also checks for missing or broken teeth.
By applying impulse hardening just on the tip of each tooth, the teeth is hardend up to Hv900 to Hv1200.
This technique is only done on the surface of the teeth. Surface is super hard, but inside the steel is still ductile and strong against friction.
Impulse hardening is a process of heating the tip of the teeth using electrical current for just 0.003-0.006 seconds. This results in a very hard structure.
We came up with our original machine that can heat each tooth a hundred times in a second.
The impulse hardening process is now much faster while the quality meets our high standard.
It takes longer time to heat wider area and cooling slows down, so hardness doesn't increase as much.
Also if heating is applied a number of times to the same spot, not only the surface but also the inner core is heated. This could cause the teeth to break. Therefore, we harden each tooth at a time.
The part that's black is where it was heated by impulse hardening.
A handsaw consists mainly of three parts. They are the blade, the handle, and the metal spine. We assemble these parts and finally have a finished product.
A band and a safety stopper is attached to the sheath.
We have approximately 90 types of saw blade.
Including different types of handles and spare blades, there are 200 different types of packaging.
Packaged products are ready to be sent to Gyokucho Industry where they are sold to distributers.