Shaft Keyway Depth and Length Increase

You should check in the first place what causes the wear.

Keys and key ways must be function of the torque and power, established on the gears or pulleys that are applied. Are you talking about a stepped shaft or a stepped pulley?

For a shaft of 90.2 mm your key way looks small to me, or your shaft very big.

Most keys and key ways wear because of too much play, caused by loose attachment or undersized key or bad skill. You should take care of the size and adjust both ways and make a key that fits.

A pressure screw on it and one rotated over 90 degrees is most common.

But the main problem might be the tolerances between, shaft- key ways- key and pulley or gear.

Well to me , based on Root cause analysis , it seems that insufficient keyway depth lead to shear failure because the impeller became loose on the shaft and caused damaged on the shaft surface .

I have checked using BS 4235 and it says the shaft width n height to be 22x 14 mm against the present 18x 8.5 mm . So it seems , this can be one of the main causes .

Does the length of keyway also effect any loading / stresses of shaft ..?

Yes, length distributes force over area. If the keyway is failing, bringing it up to spec would be a good move.

Yes, especially when the shaft ends and only one bearing on the side. Do you see shear on the key? (like it has shear marks, similar to the beginning of a cut) or only wear on shaft, impeller and key. How does the impeller fits on the shaft? Size and play? H..? If this shows wear or is too loose, even making a new key or adjusting your keyways might lead to the same defect. Is the shaft tapered or cylindrical? How is the fixation and the HP rate of the drive? You can try with a slightly over sized key and adjust it by hand with a file or sandpaper. And use a filler (liquid) glue to deal with minimal play. And take care of imbalance and vibrations.

Thanks friends for your valuable suggestions

Let see keyway depth and length is depends upon shaft diameter, lenght and stress that directly affect on shaft. But most thing that is use of shaft like in rotory manching or reciproceting maching or both contain machine. So when ever you design for shaft or any thing first consentrate on use of that thing.

1. What is really failing? Keyway, or key?

2. Do you understand the function of the key? Or keyway?

3. Do you realize that making the keyway larger makes the shaft weaker?

4. Are you prepared to replace the more expensive parts that will fail after you make the keyway, or key stronger?

A friend pointed me to your posting because we have a decent solution for your problem. We manufacture a keyless clamping hub for high-performance applications. It is used very frequently on keyed shafts where the keyway is filled with a half key (mostly for maintaining balance). The hub carries the torque in friction rather than rely on the key. If you need more information, you can look at the 'keyless hub' section at couplingcorp.com.

Good luck.

Sorry, but my spam filter wouldn't allow "shaft length increase" through

Codes and torque have been mentioned by others so I wont waste space on that. I will mention that if this on a drive that reverses then it is very important to have a key properly fitted to the key way. A small amount of play in a drive that rotates in one direction is tolerable (although not desirable) because at start up the slack is taken out. But on reversing drives, the shaft can slip and hammer the heck out of the key. Each time this occurs the key deforms and the distance increases between the key and the key way until the eventual shearing of the key.

When replacing a sheared key inspect the shaft and hub for damage to the key way. Slight rounding of the corners of the key ways allows room for a key to deform as it is not properly supported. Also the side walls of the key ways can become tapered. Tapered walls can allow the key to twist under load and result in repetitive key failure. Re-machining the key ways is preferred in my shop. Loctite and like products might work if they can handle the compressive loads. I am guessing if the steel key is failing then loctite might not be an option. But again this depends on the load.

dear sir,

as per your speck depth only 4 mm, this have take only less torque .

So ,you need to change depth 18 mm & with 18 mm but length as it is same.

pls try it.

warm regards,

balaji

On shallow depth key-ways the keys are usually pressed in. All keys will fail if the side fit is not close.