Talk about household scissors. More precisely - about a screw that does not unscrew and does not twist during operation, that is, it stops. With the help of this screw, the force of pressing the canvases to each other is regulated.
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Simple household scissors consist of only three parts - two sheets (blades) and an axis that connects them. The axis is made in the form of a rivet or screw.
Although seemingly simple, scissors are complex cutting tools with precise cutting blade geometry.
Sometimes even sharpened scissors do not cut.
In order for the scissors to work efficiently and for a long time, not only the sharpness of the blades is important, but also the correct adjustment of the convergence of the blades so that they do not diverge and do not close too tightly.
The screw allows you to adjust the compression force of the scissor blades using an ordinary screwdriver.
But over time, the scissors wear out and become loose. Again, adjustment is required.
To lock the screw, its end is sometimes flattened. In this case, adjustment with a screw and disassembly of the scissors for sharpening is no longer possible.
I decided to do it differently.
I made frictional locking of the screw. Locking is necessary so that when the scissors are working, the screw does not screw in or turn out, so that the force of pressing the sheets against each other does not change.
Friction locking made in the thread.
This could be done by making the internal thread (in the canvas) incomplete, that is, reducing its diameter. But in my case, there is already an internal thread in the canvas.
Therefore, I have only another option - to make a more complete thread on the screw.
It is shown how I make such an M4 screw.
To do this, in order to make a more complete thread on this screw, I used an M4 split die. I unclenched it in the die holder with a screw.
How I cut the dies is shown in my video “Cutting the dies with a DRILL on a JMD-1 milling machine”:
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Collected scissors. The screw turns hard. Okay.
Adjusted screw. Scissors cut thin silk fabric and plastic film well. The screw does not twist and does not unscrew during operation.
Here is the frictional locking of the screw I made in simple household scissors.
In professional hairdressing scissors, not just a screw is used as an axis, but a whole assembly, including up to 12 elements.
The blades of the scissors are slightly curved towards each other. This is done so that when cutting, the cutting edges of the blades always close, in any position.
If you look at the scissors from the narrow side, you can see that the canvases intersect.
The blades of the scissors are curved so that after folding their ends close together, and a small gap forms along the cutting edges.
Here is such an interesting cutting tool - scissors. Two ends, two rings, carnations in the middle.
And so that the force of pressing the canvases to each other does not change during operation, frictional locking with a screw with a more complete thread can be used.
5 мар 2022
