Removing bad mast/carriage rollers is one of those jobs that can be very difficult especially if the unit is used primarily outdoors or is old/poorly maintained. If the roller is stuck or corroded or has broken and all that’s left is the hub on the stub shaft it can be very difficult to get behind it to pry it off. There are some definite do’s and don’ts a tech should keep in mind if you are dealing with this scenario.
Too often we see technicians hit a hardened steel mast roller with a hammer, punch, chisel or pry bar trying to dislodge it. Many steel tools and components are hardened, or contain components made from hardened steel. For example: hammers, chisels, punches, pry bars, drill bits, cutting tools and various machine parts. Bending, twisting, sudden impact against two hardened surfaces, or even applying extreme force to hardened steel tools or implements could result in shattering and sharp metal fragments (shards) being ejected at very high speed.
If the roller is still intact, you can usually apply some penetrant and use even force on 2 sides with pry bars to break it loose and ease it off. If you are unable to or the hub is all that is left, consider using a cut off wheel, while wearing the proper PPE and the guard in place to make a diagonal or crosscut to remove the stubborn roller. You may have to cut the outer race away first if the roller is intact and then the hub, but once your cut is made the tension will be released and you can usually pull it off much easier. One thing to keep in mind is to avoid cutting too deeply and damaging the surface of the stub shaft. If you cut too deeply and get into the stub shaft, you just made the job much bigger.
- When a hardened steel part requires impact to loosen or dislodge it, the tool used should be made of a softer material such as a brass hammer or brass punch to prevent shattering and injury.
- Tools such as punches, hammers and pry bars are not lifetime tools, they will wear and become damaged and unsafe. If either end of a chisel or punch or the face of a hardened hammer is mushroomed or chipped/split, toss it in the recycle bin and replace with a new tool.
- As part of your Task Hazard Analysis consider the safest way to do the job and account for stored energy release. (what is my hand going to smash into if the pry bar/punch/hammer slips)
- Always, Always, Always wear your PPE! There is never a valid reason for not wearing your safety glasses, face shield, appropriate gloves or any other PPE that a task requires.