Dan Anderson: Shaft Repair: Take Time to Save Time

March 15, 2019 04:24 PM
 
Removing a pulley, sheave or hub from a shaft can be a breeze. I know because it’s happened twice in my career as a mechanic. The other hundreds of times the removal took one or more approaches and multiple tools.

Removing a pulley, sheave or hub from a shaft can be a breeze. I know because it’s happened twice in my career as a mechanic. The other hundreds of times the removal took one or more approaches and multiple tools.

When removing a pulley, sheave or hub (hereafter PSH) from a shaft, take time to save time. Use emery cloth to remove paint or rust from the end of the shaft. Soak the shaft on both sides of the PSH with penetrating oil and let the lubricant wick between the hub and shaft. Remove set screws or bolts and fill holes with penetrating oil.

There have been times when I tried to rush a repair without lubing the shaft, and the component refused to budge. I then took time to soak things with penetrating oil, and when I returned a couple hours later the PSH easily came off. Lesson learned.

Once things are prepped for removal, my first choice is to use an air hammer to “buzz” off a PSH. Put a pointed bit in the air hammer, use a long pry bar to pry outward on the component and “buzz” the pointed bit into the end of the shaft. If an air hammer is not available, the same effect can be achieved by pounding a punch against the end of the shaft while prying outward on the component. But that approach takes two people—one to pry and one to hold and hammer the punch. Trying to pry outward while hammering directly on the end of the shaft without a punch, even only a few blows, will mushroom the shaft and make removal even more difficult.

Be sure to keep the bit—or punch, if using a hammer—centered on the end of the shaft. If the bit or punch walks off the edge of the shaft it will mushroom or mar the shaft enough to prevent the PSH from coming off.

Be cautious when buzzing and prying on large-diameter sheet metal pulleys. Pry only against the hub immediately adjacent to the shaft to avoid bending or bowing the circumference of the pulley.

If the PSH refuses to move after a couple extra “buzzes,” use judicious heat from an acetylene torch to expand the metal of the hub, then buzz it again. Put extra heat into problem areas near keyways, set screws and set bolts.

When removing cast iron or machined PSHs, it’s possible to use a wheel or gear puller. There are numerous brands of pullers, but Posi-Lok pullers are the only brand I keep in my toolbox. Posi-Loks have a “cage” around the jaws that makes them easier to install and much safer to use. This isn’t a product endorsement—it’s a fact.

Many cast or machined PSHs have split hubs, with a 5/16" or 8 mm bolt clamping the split hub to the shaft. After removing the clamp bolt, soak the gap in the hub with penetrating oil, then tap an appropriate-size cold chisel into that gap, parallel to the shaft, to spread the gap and loosen the hub’s grip.  

Some cast iron/machined PSHs have two or three threaded holes in the center hub parallel to the hub’s axis. There are two ways to use those threaded holes, which are there to make removal easier. If there is a solid, flat surface behind the holes, thread long bolts through those holes until they bottom against that flat surface. By carefully cranking each of the bolts a half-turn at a time, the PSH can be “pressed” off the shaft.

The second way to use threaded holes in a hub is to install a two-arm T-bar puller on the end of the shaft, put long bolts through the arms of the puller into the holes in the hub and pull the PSH off the shaft with the puller. Again, use lots of penetrating oil and heat the hub with a torch.

Heat from a torch is often the magic that also loosens PSHs installed on tapered shafts, but proceed with care. After installing a gear puller, always install a bolt and washer or retainer in or at the end of the shaft. When the puller is tensioned and heat abruptly loosens the PSH’s grip on a tapered shaft, it often releases with a literal “bang” and tries to shoot off the shaft. The bolt and washer or retainer are insurance no one gets hurt.


As a farm machinery mechanic and writer, Dan brings a hands-on approach that only a pro can muster. Read Dan's blog here.

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Comments

 
Spell Check

Jeff
Camp Hill, PA
3/19/2019 07:06 AM
 

  A can of heat riser lube is a sure cure for nearly anything stuck; be it a bold or item stuck on a shaft. I find the General Motors brand works best, and would not be without it as a sure cure. My son was beating and heating a u-joint that would not come apart. A shot of GM heat riser lube and a few minutes - it came right apart - he now keeps a can in the shop.

 
 

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