Controlling shaft key
- Thread starter dehler25
- Start date
Am not sure about your arrangement but here are ideas that work for any keyed shaft.
Gently tap to expand the shape of the the key using hammer and anvil (or similar) just enough so it fits tight in the shaft keyway. File the impeller keyway so the key slides freely in the impeller keyway.
To assemble - press/tap the key into the shaft keyway (it is now held held solid because you have enlarged the width of the key.) Then slide the impeller on. The impeller will slide on smoothly because you have filed the impeller keyway such that there is no interference with the key.
Charles
Gently tap to expand the shape of the the key using hammer and anvil (or similar) just enough so it fits tight in the shaft keyway. File the impeller keyway so the key slides freely in the impeller keyway.
To assemble - press/tap the key into the shaft keyway (it is now held held solid because you have enlarged the width of the key.) Then slide the impeller on. The impeller will slide on smoothly because you have filed the impeller keyway such that there is no interference with the key.
Charles
The trick is to ensure the key is fully seated in the shaft by light tapping or squeezing it in with some smooth jawed pliers.
Some good ideas to persuade the key to stay in place, I also thought of placing a bit of Teflon tape to create a bit of interference fit. I took a break as I was getting irritated and it could wait. The key was deeply set it still could rotate along its curved bottom, if the tape doesn't do the trick I will try to deform it ever so slightly.
I usually use grease to hold a key in place for assembly in a slip fit keyway. In extreme cases, I have been known to drill through the key & tap a thread in the bottom of the keyway so that I can use a small machine screw to hold the key in place. The hole will either need to be countersunk or counter bored, depending on what type of screw you want to use. I usually also file a small ramp in the front edge of the key to help it slide into the broached female keyway above the shaft, rather than hit against it & push out of the keyway in the shaft.
If I am installing a pres fit key in a shaft & I expect to have difficulty removing it in the future, I will again pull out the tap. In this case, I will tap a thread into the key so that I can use a jack screw to remove it in the future.
If I have a tight key with no jack screw thread in it & no suitable tap/screw available to remove it, I have been known to drill an 1/8" hole in the key, fill it with grease, put a tight fitting 1/8" pin punch on top of the grease & hit it with a hammer. The hydraulic pressure of the grease will usually break the key free & budge it out of place by a few thousandths. I then try to get a grip on the key with pliars & remove it. If that doesn't work, I go to vice grips, which usually damage the key & require subsequent replacement of the key or dressing of the key with a file, if you are going to use the key again. If that doesn't work, then I have been known to reach for a 1/4" cold chisel & a hammer. I chisel a groove into the edge of the key & then change the angle to hammer the key out of place. At this point, you are abandoning the key & planning to replace it.
If I am installing a pres fit key in a shaft & I expect to have difficulty removing it in the future, I will again pull out the tap. In this case, I will tap a thread into the key so that I can use a jack screw to remove it in the future.
If I have a tight key with no jack screw thread in it & no suitable tap/screw available to remove it, I have been known to drill an 1/8" hole in the key, fill it with grease, put a tight fitting 1/8" pin punch on top of the grease & hit it with a hammer. The hydraulic pressure of the grease will usually break the key free & budge it out of place by a few thousandths. I then try to get a grip on the key with pliars & remove it. If that doesn't work, I go to vice grips, which usually damage the key & require subsequent replacement of the key or dressing of the key with a file, if you are going to use the key again. If that doesn't work, then I have been known to reach for a 1/4" cold chisel & a hammer. I chisel a groove into the edge of the key & then change the angle to hammer the key out of place. At this point, you are abandoning the key & planning to replace it.