How To Cut A Key Slot In A Shaft Without End Mill

Always done them with and end mill. First shop I worked in, we did them by plunge cutting first, about .05 per step, to just shy of depth, then set the quill and ran a pass to finish things up.
 
Pmedic828 said:
Does anyone know how to cut a key slot in a shaft without using an end mill? Watched various youtube videos watching machinists work and on more than 3 sites, the machinists said not to cut a key slot in a shaft with an end mill because the end mill would either chip because it is hitting 2 sides at the same time, or it will wonder and not produce a straight slot. They, however, didn't explain how to do it with magic? Can anyone enlighten me?
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That is a good deal of misinformation right there, a side milling cutter works well for long external key ways also. You mention watching videos of machinists on youtube, are these people that do it for a living or hobbyists?

As far as magic goes yes it exists, it is easily done with a ram EDM with high accuracy and surface finish at great expense, no one would do this for a simple keyway in mild steel however if it could be milled, EDM will produce an excellent slot in a carbide shaft for instance. One may also produce a key slot on a surface grinder if so inclined but this is also a laborious process.
 
I cut key seats on a horizontal mill almost every day. What ever you use it should have a radius on the sides at the bottom..
 
kingmt01 said:
So you cut the key slot with a radius on the conners?
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it is best practice to have a radius in the corner because a sharp corner is a potential failure point.
In practice, you can use square corners with fractional horsepower with no issues most of the time. You can probably even get away with it up to 3 HP as long as the load on the key is fairly constant.
If you start looking around at key ways, you will probably find a lot of commercial made ones have square bottoms unless they are under some kind of heavy to severe duty.
 
Thanks guys. That is good information. I was thinking the only slots I've seen had sharp corners but then again I don't think I've ever looked close.
 
A sharp edged notch increases stress 4 to 16 times. This increases the possibility of fatigue fracture failure. This was part of the metallurgical failure analysis classes I took at Caterpillar.
 
royesses said:
A sharp edged notch increases stress 4 to 16 times. This increases the possibility of fatigue fracture failure. This was part of the metallurgical failure analysis classes I took at Caterpillar.
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Is there any standard/guide as to when the notch goes from having a ever decreasing radii to being sharp? Asked another way, is there a radius that is too small that is effectively a sharp angle or is it material dependent?
 
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