Johansson gauge blocks

T

The_Observer

Member
I came across a video that was explaining the history of precision and tools. It was very interesting. The foundation of precision is from the surface plate which can be created with 3 irregular planes, because the common plane between 3 irregular planes is a perfectly flat plane.

Anyways onto the point: Johannson gauge blocks. They were originally created as a basis of precision measurement to gauge your tools on a regular basis. It was more or less the beginning of standardization between measurements as up until that point, an inch was anywhere between 22-25mm depending on how it was defined.

What I find so interesting about these blocks is that they are so flat and so precise in measurement, that they literally stick to one another seemingly without any explainable reason. No one knows if it's because of molecular adhesion, or the surfaces being so flat they press out all air and are sticking together through external atmospheric pressures; or a combination of factors.

I'm interested to see what input others have on these blocks and what you think makes them stick together?

 
The_Observer said:
I came across a video that was explaining the history of precision and tools. It was very interesting. The foundation of precision is from the surface plate which can be created with 3 irregular planes, because the common plane between 3 irregular planes is a perfectly flat plane.

Anyways onto the point: Johannson gauge blocks. They were originally created as a basis of precision measurement to gauge your tools on a regular basis. It was more or less the beginning of standardization between measurements as up until that point, an inch was anywhere between 22-25mm depending on how it was defined.

What I find so interesting about these blocks is that they are so flat and so precise in measurement, that they literally stick to one another seemingly without any explainable reason. No one knows if it's because of molecular adhesion, or the surfaces being so flat they press out all air and are sticking together through external atmospheric pressures; or a combination of factors.

I'm interested to see what input others have on these blocks and what you think makes them stick together?

Click to expand...

I would go with the atmospheric pressure effect as the external source causing the plates to stick. Although there is the Casimir effect too.
 

Einstein said:
I would go with the atmospheric pressure effect as the external source causing the plates to stick. Although there is the Casimir effect too.
Click to expand...
Thanks for your input. It seems to me that the more precise in nature we get, down to the molecular level, the more we see strange quantum-like behaviors. So much we don't know - yet we think of ourselves as intelligent and modern. The more I come to learn, the more I realize that I actually know nothing.
 

Gauge block - Wikipedia

Wringing is the process of sliding two blocks together so that their faces lightly bond. Because of their ultraflat surfaces, when wrung, gauge blocks adhere to each other tightly. Properly wrung blocks may withstand a 75 lbf (330 N) pull.[5] While the exact mechanism that causes wringing is unknown,[5][6] it is believed to be a combination of:[4][5]
  • Air pressure applies pressure between the blocks because the air is squeezed out of the joint.
  • Surface tension from oil and water vapor that is present between the blocks.
  • Molecular attraction occurs when two very flat surfaces are brought into contact. This force causes gauge blocks to adhere even without surface lubricants, and in a vacuum.
It is believed that the last two sources are the most significant.[4]
There is no magnetism involved, although to a user the clinging together of the blocks feels a bit like weak refrigerator magnets sticking together. Unlike magnets, however, the cling only lasts while the blocks are completely joined—the blocks do not attract each other across any visible gap, as magnets would.
The process of wringing involves four steps:[4]
  1. Wiping a clean gauge block across an oiled pad (see the accessories section).
  2. Wiping any extra oil off the gauge block using a dry pad (see the accessories section).
  3. The block is then slid perpendicularly across the other block while applying moderate pressure until they form a cruciform.
  4. Finally, the block is rotated until it is inline with the other block.

After use the blocks are re-oiled or greased to protect against corrosion. The ability for a given gauge block to wring is called wringability; it is officially defined as "the ability of two surfaces to adhere tightly to each other in the absence of external means." The minimum conditions for wringability are a surface finish of 1 microinch (0.025 μm) AA or better, and a flatness of at least 5 μin (0.13 μm).[4]
There is a formal test to measure wringability. First, the block is prepared for wringing using the standard process. The block is then slid across a 2 in (51 mm) reference grade (1 μin (0.025 μm) flatness) quartz optical flatwhile applying moderate pressure. Then, the bottom of the gauge block is observed (through the optical flat) for oil or color. For Federal Grades 0.5, 1, and 2 and ISO grades K, 00, and 0 no oil or color should be visible under the gauge block. For Federal Grade 3 and ISO grades 1 and 2, no more than 20% of the surface area should show oil or color. Note that this test is hard to perform on gauge blocks thinner than 0.1 in (2.5 mm) because they tend not to be flat in the relaxed state.[4]
 

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