Introduction: Shop Cheats: Bushing/bearing Removal

This Instructable will be yet another in my series of Shop Cheats. I had forgotten about this cheat until my current round of equipment repair. There were some bushings in need of replacement but proved difficult to remove from their bore. These particular bushings wanted to chip and break apart when struck with a punch. Which as you can imagine makes driving a bushing quite difficult.

Then I remembered how to cheat. A little something I seem to have picked up while learning to become a mechanic. A bushing is basically an inside diameter, and all I needed was to make it slightly smaller. Welding is an excellent way to shrink metal if properly preformed. Since the applied weld material is very hot it will shrink as it cools. So by welding a bead across the bushing, I ever so slightly change its outside diameter. Thus loosening it in the bore. This technique can be applied to both bushings and bearing races. And can be applied multiple times to the same bushing or bearing if needed.

A few notes. Be very careful about where you strike an arc. If you inadvertently weld off the bushing or bearing you run the risk of ruining the part. The hotter the weld the better. Size however is less important. The bushings I removed were quite thin, and would not hold up to a lot of heat. Because of this I could have burned through the bushing and into the surrounding part. Which was something I was very careful to watch.

Comments

author
boxbbcar (author)2015-01-06

Agree with Nitsuj1098. I was skeptical first time I tried it (recommended by my BIL, a master mechanic) but it works slick as anything. Only weld about half way around the race, will either fall out or require slight tap

author
nitsuj1098 (author)2014-12-10

You'll find it works best of you weld around the entire inner circumference of the stuck race. I've had outer races hopelessly stuck in wheel hubs, only to weld around them and have them literally fall out. Never had this method fail. Heating the part on the outside can warp it, or in the case of something like a motorcycle wheel hub, harm its appearance. Liquid nitrogen and dry ice are rarely found in an automotive shop, but there is always a welder around. And with a mig welder, its almost impossible to damage the part. Just put the tip where you want it and keep it there. Great tip.

author
carlos66ba (author)2014-12-06

I woud add dry ice or liquid nitrogen, or use an inverted "compressed air" canister to cool the inner part, thus shrinking it.

author
Metal_maestro (author)carlos66ba2014-12-06

In my experience the use of cryogenic gas is underwhelming. It works pretty well for installing parts. Mostly due to being able to control what is being cooled. It takes a long time to suck heat out of a piece of metal. Even with liquid nitrogen. The movies have taught us to believe that it has a much greater specific heat than what it actually does. With these bushings being as thin walled as they are they would conduct heat from the surrounding part. Causing both to contract at nearly identical rates. If it were possible to shock the bushings to the temperature of liquid nitrogen in less than a second it would probably work. But heat will still be trying to get into them. And the work window would be short.

author
tomatoskins (author)2014-12-06

I would be a little concerned about accidentally damaging the part. If you are looking to make something expand or contract couldn't you just use your oxyacetylene torch to cause the outside to expand and then slide your bushing out?

author

It is an option in some applications. However the risk of thermal warp from heating the part is high. The bushings are cheaper than the part, as they are intended to be. So destroying them is the better option. Plus you have to consider which part is the greater heat sink. The bushings here are maybe a couple of ounces, and therefore will change temperature quickly. The part itself is several pounds and will require a much greater volume of heat to expand. Plus the bushings are in direct contact with the part and will change temperature at almost the same rate. Possibly even expanding more quickly, as they have a high copper content and are more conductive. Basically the rules at work here are the same as welding a light sheet metal to heavy stock. The heavy side of the equation will take more energy to reach critical temperature. While the lesser side will try to flash melt.

author
Orngrimm (author)tomatoskins2014-12-06

schould work. but with the weld, it is a permanent shrink. you take out the element of time with a world. with just heat the external pipe (or cool the internal one) you have yo hurry much more than with a weld.
or at least that's how is understood it... ;)

author
Metal_maestro (author)Orngrimm2014-12-06

The weld permanently alters the bushing. It will actually become smaller, at a very lesser rate, as it cools. Heating the exterior part is unacceptable in this application as it could thermally warp the part. The bushings are maybe $5 (US) on the high side. Where the part they belong in is easily 30 times as much. Plus the rate at which the heat would be absorbed by the materials involved the bushing would expand as fast or faster than the part.

author
Orngrimm (author)2014-12-06

Eh... So you welded one/a few lines INSIDE onto the bushing to reduce its side by thermal contraction?

The actual procedure is not very clear from the pictures, sorry.

author
Metal_maestro (author)Orngrimm2014-12-06

Yes, the welds are inside the bushing.

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Bio: I am a shop body. Give me a job, the tools to do it, and I will be happy as can be. I get along ... More »
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