Pressing a shaft out

[drummerdimitri]

I bought a used industrial polishing machine and currently in the process of restoring it to as close as new as possible.

I have take the arm off that houses two bearings on each end and a shaft that goes all the way through.

My new hydraulic press should be arriving soon and I would like to press the shaft out of the housing to clean and regrease it.

Since I have no experience with such a job, I wanted to ask for guidance so that I don't end up breaking the part as it cannot be replaced.

Is there a direction to press it out or can I press it out from either end?

I've removed anything that was previously attached to the arm and any nut/retaining ring on the threaded portion of the shaft and it now rotates freely but hammering the shaft only moves it a few millimeters each way but wont remove it completely.

 

[alfadan]

Only thing I can offer is to make sure there are no burrs on the shaft like around keyways that could gall while passing through the housing. Protect the threads and end of that tapered end to make sure it doesn't mushroom. It may appear to be fine visually, but could be damaged while pressing or hammering.

 

[GeoBruin]

In addition to the comment above, pressing on one end of the shaft may (however slightly) mushroom it if the force is applied at all unevenly. As such, push on the end of the shaft that had the least critical dimensions. To my eye, it looks like the shorter end has some kind of taper to it. If that taper mates with something else, I would be concerned about marring it. It also looks like it has a (possibly threaded) hole. I wouldn't want to damage the hole/threads.

All that said, make sure you put something soft or otherwise secure the shaft when you're pressing it out. You don't want it to come out the bottom and smack the concrete floor. Speaking from experience here.

 

[drummerdimitri]

Only thing I can offer is to make sure there are no burrs on the shaft like around keyways that could gall while passing through the housing. Protect the threads and end of that tapered end to make sure it doesn't mushroom. It may appear to be fine visually, but could be damaged while pressing or hammering.

I already removed the keyway that was located on the shorter end of the protruding shaft on which a belt sheave would attach to so that wont be an issue.

First time I saw one with a retaining screw. Nowadays they are just held in place by friction or grease!

 

[drummerdimitri]

In addition to the comment above, pressing on one end of the shaft may (however slightly) mushroom it if the force is applied at all unevenly. As such, push on the end of the shaft that had the least critical dimensions. To my eye, it looks like the shorter end has some kind of taper to it. If that taper mates with something else, I would be concerned about marring it. It also looks like it has a (possibly threaded) hole. I wouldn't want to damage the hole/threads.

All that said, make sure you put something soft or otherwise secure the shaft when you're pressing it out. You don't want it to come out the bottom and smack the concrete floor. Speaking from experience here.

It does look indeed to be tapered, will have to make sure of that.

Not sure why though as the sheave that slips on is retained by a bolt and there is a keyway to prevent it from slipping.

The less critical dimension would definitely be the longer end of the shaft.

Will be using a large bucket filled with metal chips to soften the impact as it falls out of the housing.

 

[seber]

That taper looks like it is already bulged at the end. Did you hammer on that?

 

[alfadan]

I already removed the keyway that was located on the shorter end of the protruding shaft on which a belt sheave would attach to so that wont be an issue.

First time I saw one with a retaining screw. Nowadays they are just held in place by friction or grease!

I like to take a very fine file, very lightly to shafts especially around the keyway slots before pressing just in case there is a burr possibly raised by previous bearing/pulley installation, grit caught under said bearing/pulley.

 

[RoninB4]

-When pressing bearings it's important to note that:

1) Bearings going on shafts get pressed on the inner race
2) Bearings going into a housing get pressed on the outer race
3) Bearings already installed on a shaft that are going into a housing get pressed on both inner and outer race at the same time

Sometimes a deep well socket can be used that matches either the inner or outer race but for pressing on both a special installation bushing needs to be made. Failure to follow these guidelines on disassembly/installation will likely result in micro-dimpling of either/both races and the balls/rollers. Can you achieve installation without following the guidelines I've listed above? Probably but the bearing will probably be short lived after doing this. Whenever I extract a bearing I expect to replace it. Bearings are not as robust as most people think they are and don't survive well with random removal/installation methods. Don't take my word for it, read up on what "brinelling" is and is caused by. My own experience as a machine tool builder, reading, and consultation with a friend that works for NTN Bearings confirmed my assertions.

There's an outside possibility that applying heat to the housing will, by thermal expansion, allow the bearing to come out with a minimal amount of tapping (with a soft face hammer/drift) but I wouldn't count of it. I would try to work from the short end, there's less distance to travel out of the bearing. You really will need to inspect the bearing by feel, it should consistently smooth in rotation. Anything other than smooth, regardless of how small, should be regarded as a bearing that should be replaced. If you have that already then the bearings need replacing anyway and no amount of cleaning/greasing will help that. The vibration from a bad bearing in an industrial buffer will likely show up as chatter marks in the work. If you replace the bearings don't go for the cheapest maker, there's an ocean of cheaply made bearings from China that aren't worth installing. The advice on finely filing any burrs is good advice, same goes for mushrooming the end of the shaft from hammering/pressing on it. Good luck.

 

[drummerdimitri]

That taper looks like it is already bulged at the end. Did you hammer on that?

Not at all.