## Hand Tools Archive

Subject:
Re: Some things to calculate
Response To:

Kees
Well, I've been thinking a bit about this. The last physics education I got is 20 years ago, so I am a little rusty on these things. When we have a mechanical engineer overhere, please correct all my false assumptions and miscalculations.

So in the video we have a splinter of wood, 9mm wide but only propagating 0.2mm deep into the wood (depth comes from looking how far the split goes in the Kato video). That splinter manages to excert a force of -0.5 kgf. That means, the wood forces the cutting blade down.

A smoother made with such a blade would have an area under the frontknop of about 9 x 50mm = 450mm2. But you only need to press down that narrow sliver of wood, 9 x 0.2mm = 1.8mm2. So you will have to put a downwards force of (450/1.8)x0.5 = 125 kgf on the front knob.

Now, you have seen me in my video. I don't really look like a 125 kg man, do I? If I would lean with all my weight on the front knob of the plane, I could only muster half of the neccessary force on the woodchip to hold it down into the wood.

Conclusion, to be able to use the mouth to prevent tearout, you will have to hollow grind your plane sole, like the japanese do with their planes.

Of course I could easily be off a factor of 1000 or so, so please verify my calculations.