Bearing Installation Temperature

I assume you are looking for a shrink fit, that's why you want to heat the bearing. If the bearing is a sealed bearing, heating is not a good idea, you should go for a press fit, not a shrink fit.

But, if you are insistant on this type of assembly, you need to let me know how much interference you have, and the exact co-efficient of expansion of the material of the bearing.

Coefficient of expansion X change in temp. X Diameter of the bearing.

That will give you the size of the bearing once you heat it up, compare that to the size of the shaft.

If you don't know how to do that, reply with the bearing size, material, and shaft size and I'll give you the answer.

Laby

In the bearings data sheets you find for each type indications in the technical part how to assembly it. Usually the tolerances for the shaft or the housing are specified so that you can apply what laby wrote and you can determine the temperature.

Several manufacturers (SKF, FAG and other) even sell specific heaters (induction) and give indications for the temperatures.

Follow manufacturer's specifications.

As said above, follow the manufactures instructions however:-

Applying heat to the bearing would get it onto the shaft but what are your intension's for getting the outer shell down the hole? Do you propose to then drop the shaft and bearing assy' into liquid nitrogen or heat the hole?

I don't like the sound of any of it as repeatability will be the problem and cracked bearing races the end result!

If you are going to heat any bearing, for what ever reason, do not heat it above the maximum rated temperature for the lubricant that has been applied to it. If you degrade the lubricant and it starts to breaking down, even if you clean it and replace the lubricant, you will amost certainly experience premature failure of the said Bearing.

for just run of the mill shrink fit bearings (like motors and such), I heat to 220-230 deg. F. If you have access to one, an inductive type clamp on heater works great. Beats the hell out of the old days of heating the bearing in an oven/oil bath.

Thanks. That's the info I was looking for. I am purchasing an induction heater.

You need to know several things first assuming that since you are shrinking the bearing on to shaft it is an interference fit.

Interference is a fit that allows for a relative amount of tightness between two or more assembled components. The factors to determine the interference are: Speed, Load, Torque, Assembly of Dissimilar Metals.

There are several different types of interference:

Impact interference- a fit that allows components to be installed by impacting (in the right place with right tools) Generally limited to small parts, bearings 2" or less. A general rule for this fit is that the interference will be less than 1/2 thousandths of an inch per every inch of shaft diameter. Remember you will be impacting on the inner race only

Press/Pressure Interference: type of fit that you will use an Arbor press (not a pressure fit)This fit is typically used to install bearings on shafts that exceed 2" in diameter. The general rule for this fit zone is an interference fit between 1/2 and 1 thousandths of an inch per inch of shaft diameter. Component parts 4" or less are generally acceptable for this mounting. An arbor press is one that has a handle where you mechanically apply the pressure to mount the bearing. On shafts that are 4" or bigger you will have to use hydraulic pressure because you have a greater surface area to fit and an arbor press(with you on the handle)want be able to overcome the greater amount of tension created.

Differential Temperature Interference: The general rule for this type is for an interference greater than 1.0 thousandths per inch of shaft diameter. This could be either a Shrink fit are an Expansion fit. Shrink(heating)-i.e bearings on shafts, expansion(cooling)-i.e installing stub shafts, case rings, etc.)

Excessive Interference: The general rule for this fit is when you have more than 2.0 thousandths of an inch, per inch of shaft diameter. Here you will use both heat and hydraulic pressure to install component.

Remember, all of these require that you use the right tool in the right place and you will maintain all of the radial internal clearances of the bearings.

Also when installing bearings (someone mentioned about the outter race in another responce) you need to know what the application is so you can determine whether you will have that interferece fit or slip fit. Is it an rotating shaft with an inner ring with a mean fit tight and outter ring with a mean fit loose? Is it a stationary shaft with outter ring rotation and a mean fit tight and an inner ring loose? This can get real muddy fast, if you aren't familiar with the mechanics of maintenance. There is a lot of subject matter when you get into fits and tolerances.

I have some different charts for Interference and Clearances (thats another story that I will be glad to e-mail or fax to you.

G.C, Precision maintenance instructor/consultant, Georgia Pacific, southeast region, Port Hudson, La.

If you receive the data from G. C. Precision I would be interested in a copy.

Thank You

Mike Sidon

are you talking about cup and cone tapered bearings???? my bearing people (tempkin) tell me a tight slip fit is recomanded. I use 3-5 inch cup and cone daily and the specks give me .0015 slip fit

If your dealing with tapered bearings(tapered shaft), like spherical then the bearing will come with a certain amount of clearance which you will take some of it out on installation. You will find your un-mounted clearance and look at the bearing chart for how much reduction you have then take the bearing down to it's final set point. (like going from .017 down to .010).

For cup /cone depending on whether you have a single bearing are double(face/face, back/back). On a single (like wheel on car) you have a stationary shaft so you would have an outter ring rotation- mean fit tight-at the cup. With the inner ring loose at shaft- the reason they told you-SLIP fit. You set this bearing clearance(looseness) by takeing up on lockwasher/nut when you install the hub with cone in it, this holds it all together.

Remember that Bearing manufacturers will give you a larger bearing clearance because they don't know how you will install it, how good of a fit you are installing it on etc., all of this because the old saying to Cover Your A-- , well they cover there's.

Follow the bearing manufacture's recommendation for fit. Bearings are designed to operate with a predetermined fit. Too tight the bearing will overeat and seize. Too loose and the balls,rollers,needles will skate.

Usually you can press the bearings on the shaft or in the housing. Never both. It depends on the relative rotation of the shaft and housing. Again follow the bearing manufactures recommendation. If you choose to heat the bearing use a bearing heater that is designed for just that.

If I am repeating what has already been said I apologise.

A simple rule of thumb assuming your shaft is machined to the correct size for the applied bearing is 80 to 90 deg C above the shaft temperature and never above 125 degC.

You can use hot oil (messy) an oven or an induction heater.

If you want all the details for a specific bearing type go to http://www.skf.com/mount/ you will have to register but this a painless exercise. Other reputable bearing manufacturers have similar sites.

120 degrees C

Thanks for the help.