DTM
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- How important is it for a parallel shaft key to be ground flat? If key measures the right size but the surface isn't especially flat, will there be any negative affects?
Our company has made our own shaft keys for many years, grinding them on the 4 loaded surfaces.
For example, let's say the pulley and shaft key seats are .5005 +/- .0005 wide.
We've made ground keys that are .4995+/- .0002 with a flatness of .0004.
We now are considering purchasing keys with a tolerance of .4990+/- .0005
The keys are measuring this width in tolerance, as long as you use a calipers or a micrometer with reasonably large anvil. However, if you put a dial indicator across it, with the key on a surface plate, The needle moves about .0015". So there is waviness to the key surface, but the high points measure in spec.
My thought is that this variation has minimal affect on the shear area, so there should be little to no difference in strength or performance. However, the key will not be bearing load onto the key seat as uniformly as if they were ground keys.
Can anyone see any issue with these slightly wavey surface keys?
Pictures showing examples of key seat in a shaft, in a gear, and in an assembly.
For example, let's say the pulley and shaft key seats are .5005 +/- .0005 wide.
We've made ground keys that are .4995+/- .0002 with a flatness of .0004.
We now are considering purchasing keys with a tolerance of .4990+/- .0005
The keys are measuring this width in tolerance, as long as you use a calipers or a micrometer with reasonably large anvil. However, if you put a dial indicator across it, with the key on a surface plate, The needle moves about .0015". So there is waviness to the key surface, but the high points measure in spec.
My thought is that this variation has minimal affect on the shear area, so there should be little to no difference in strength or performance. However, the key will not be bearing load onto the key seat as uniformly as if they were ground keys.
Can anyone see any issue with these slightly wavey surface keys?
Pictures showing examples of key seat in a shaft, in a gear, and in an assembly.