Pressure Required to Press Bearings on a Shaft

It may be wildly variable, depending on the consistency of shaft machining.

and temp of the parts he's trying to mate together

The bearing manufacturer has been consulted, of course. ???? Proly not.

They have sent you specs, or told you that a 20 ton press will be able to press any bearings you might have. In the hands of a competent operator, any press can install bearings. If it's got the PSI.

Where I come from, size of shaft and bearing tolerances (diameter) determine the fit. Not the pressure, needed to assemble these.

Yes, but one 20 ton press can be very gentle when it needs to be.

Knowing the "size of shaft and bearing tolerances" allows the assembly of many different sizes of shafts and bearings using the same press.

We are trying to measure the pressure in kg/cm2, also trying to collect the data of actual required pressure to press these bearings

This is a good start. What do your company employed mechanical or motor rewind Engineer(s) have to say on the subject, they should know after all?

Thanks for the Inputs..

We have installed 12 Tonn Hyd Press, to press the bearings on the shaft.

We feel that the Operator skill and the Trail / Error Method can not give us the consistant good results, hence would like to calculate the Pressure required to Press in these bearings and with some Hyd valves (Electrically Operated) the exact pressure can be selected to press in the specific bearing.

By this way we would like to eliminate the Bearing Pressing Error Factor / Contribution. ane hence looking for the Calculation details for the same.

Have contacted the Bearing Manufacturer, but they have suggested the Fits required and not the Force / Pressure required to Press in the Bearings.

Vishram Lele

The motors I've repaired by installing new bearings have all been light press fits. I could remove them with very little force from a bearing (pulley) puller, or slide hammer. So you don't need killer press fit to keep bearing from spinning. So the fit is an important parameter in the machining of the shaft and bearing housing. So when you talk to your bearing support engineer make sure you have the type of fit defined.

That's my 2cents, I'm not a motor expert, but repairability and assembly are important to the design. If your using a 12 ton press, and having operator repeatability, your probably too tight on the dimensions. Too loose and the bearing spins, too tight and you damage the inner or outer bearing race, or make it a one time assembly.

I agree with ignator. I have repaced bearings on many motors of various brands of the size Vishram Lele is talking about and bigger and have never needed a press. I suggest to Vishram that he disassembles a few other brand motors, and manufactures his to the tolerances he finds in them, in conjunction with his bearing manufacturer.

But the manufacture is more correct then you know. Trying to do what you ask is fraught with way to many variables to be of much use. If all your trying to do is see that the bearings are seated fully then other means are much more reliable.

There is some tolerances in the machined shaft which would cause a change in the force necessary to press the bearing on. Some fits will have variance of two or three ten thousands of an inch. To hold better tolerances so exact to use a pressure setting on the shaft and the bearing will increase the cost. Also the ambient temperature will also change the force necessary. If bearing and shaft metals do not have the same exact composition then they will expand and contract differently.

Calculations on paper look good. But under real practice where there are many variables they don't work.

Once again we have an instance of the user, vishram lele, not understanding the process, and trying to compensate by using meaningless information.

vishram lele, if you don't understand that fit and not installation pressure are important in bearing assembly, you will continue to have failures you don't understand.

Do you understand tolerances? Interference fits? Press fits? ANSI Limits And Fits, Interference Fits,Force Fits,Shrink Fits, Ansi ...

Thermal expansion? Galling? Mechanical engineering?

Fits - Mechanical Engineering

Engineering fit - Wikipedia, the free encyclopedia

And finally, "What we have here, is failure to communicate". _{(Cool Hand Luke)}

You need a press that has much more pounds of applied force than actually required by your tightest bearing, this is a must to warranty a full insertion.

You should be focusing on how to obtain a precise stroke, particularly the stop position at the proper point thru the shaft lenght, this is how you get repeatability in the bearing position, there are at least two ways to achieve this:

Linear position transducers and a good servo-valve with its controller; or mechanical stops, that once hit, your press hyd system will drain oil to the tank, trip a pressure switch and then retract.

Don't waste the time of your company in calculations just to impress your boss, use your hands, build the thing and then measure whatever you want in order to documment and control your process.

Welcome to the real world, pal.

A fixed max. force to push into place, and in the best of the worlds, expand the inner racing surface of a bearing by a blooming ignoramus..

Yeah, that is exactly, what is missing in production, of anything!!!

The force required to press on the bearing is a function of the fit. This determination is critical to the life of the bearing.

Here is a link to one of numerous sites that deal with this matter. I think that the fit you want is js6 but you need to verify that.

In desperation you should call the bearing manufacturer and they will tell you the correct fit.

Having determined the fit, you can easily measure the force (torque) required is if you were to use an arbor press. In fact, an arbor press might be faster and easier to jig up than a hydraulic press.

I've been repairing electrical motors for more then 20 years,

To mount and to take apart small bearing 6202 - 6204- 6205 - 6206 from rotor shafts, we use a press with a force no more than max 5 000 N.In almost 95% of the cases it works with the smaller ones (6202; 6002; 6203; 6204; 6004; 6304)In about 70-80 % of the cases it also works with the bigger ones 6205; 6206; 6306.With new manufactured shaft and correct fit, you will have no problems.

Only if the shaft is rusty besides the bearing, you will need more force for these small bearing 15 000 - 30 000 N.

When you need more then 5 - 6 tonnes, there is something wrong….

In initial stage of mfg. motors of small H.P you need not invest in buying hydraulic press. You can use manual hand press. Motor mfg. in India is highly competitive field so you should carefully invest your money. We were mfg. 1.5 HP motor for Hoist and we could manage with hand press. If your rate of production is very high then you can think of hydraulic press.

Why tell you anything if you have already chosen not to listen humbly and with respect to the bearing manufacturer? Who would know more about the proper installation of their bearings than the manufacturer?

They should have the specs of the bearing ID, run out of round, etc. They should also be able to tell you the shaft specs, including the finish necessary to allow a snug fit that will not slip under service conditions. I should think you would want to press on the bearings at a temperature that matches the upper limits of temperature rating for the equipment this goes on, since if the fit is the slightest amount loose at "room temperature" cold, then it must surely slip at the upper temperature limit.

Have a look at http://www.nsk.com/services/maintenancerepairs/mounting.html?

Let me anticipate the OP's follow-up question:

"Please what are International Standard for pressing in Bearing on motor shaft?"

I used to work for a company that often installed bearings. Part of the process was to heat up the bearing, either in hot oil or in an oven. The shaft was also cooled using dry ice. After 15-20 we would install the bearing onto the shaft and seat it with a sleeve and the press. The press was used to ensure the bearing was seated properly.

The idea was not to install the bearing cold. By heating the bearing and cooling the shaft. the press fit integrity was maintained...

Problem solved, we have contacted SKF Bearing Manufacturer,got the details about the required Fits and Interferences.

Calculated the Force using the Poissons ratio and cross check the same with our Readings on Job.

Thanks a lot for your Inputs, Although some inputs are Off Topic.

I feel this forum should be used to solve the problem rather than tossing the problem in air..

Remember to apply any force to the inner race when pressing onto a shaft. That way the force is never applied through the bearing surface and it wont risk damage,

Hi,

Perhaps you can also elaborate your finding. I am sure everyone on this forum is willing to learn something too. It will prevent the "tossing around" in the future.

Thanks. D

i read this thread and i am wondering why no one has mentioned the machinist hand book,for fits and also no one has mentioned a mic .

you know there is info there about shrink fits,i am just an old machinist ,just saying.