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# Bearing Press fit

## Bearing Press fit

(OP)
Hi all, I'm new to the site and I'm trying to find an answer to this.  I currently have a cast metal wheel hub and when measured between the hub and the bearing race it is a 5000 inch press.

I have made a billet aluminum hub out of T6061.  I was thinking of making the tolerances to have an 8000 press fit for the bearing race.

So my question is how much of an expansion is there with aluminum if it were heated to say 400 degrees?

Would it expand 3000 of an inch and then I could press the bearing race in.

My concern is that the race would spin in the hub if it became to hot and under racing conditions I see this happening.

### RE: Bearing Press fit

Use the circumference of the hole and the coefficient of expansion to obtain a rough estimate of the circumferencial expansion.
Use an FEA thermal analysis to get a more accurate deformation profile.
Kevin

### RE: Bearing Press fit

You do not need to calculate the circumference change, the diameter will change the same way multiply the diameter buy the coefficient of expansion and then multiply by the temperature change to find the enlaged/reduced diameter.

circumference=PI*diameter

### RE: Bearing Press fit

(OP)
Thanks for the response what I was hoping for was that someone would be able to provide the information in regards to the rate of expansion for T6061 aliminum based on a given temp.  The OD of the alum is 3" and the thickness is about 1/4"  I have it set for a 5000 press fit but was thinking about making it an 8000 press fit.

If anyone could direct me where I could find specs like that I would appreciate it.

Thanks!

### RE: Bearing Press fit

A major supplier of aluminium in your area should be able to give you the co-efficient of expansion for the grade you are useing. It's simple maths from there

Regards
pat

### RE: Bearing Press fit

Try www.matweb.com it has data for almost every material you'll play with. 6061 has an expansion coefficient of about 24e-6 m/(m.C) or about 13e-6 in/(in.F).

### RE: Bearing Press fit

.000,013 in/in F * 400F * 2" dia = 0.010 inch diametral expansion when heated uniformly.  If the heat source is a  hard working quick heating brake rotor the hot diameter and expansion  will be much greater than 2 inch, but the heat transfer from rotor to hub will be poor, even across a hard clamped bolted joint.  A hat shaped rotor or brake hub will keep the rotor from tugging too hard on the bearing hub.

In the stuff we make (precision machine tool spindles) the heat source is often the bearings themselves. Revving up  rigidly preloaded hi-speed bearings in a thick cool housing is like manually winding an anaconda around Jon Voight.  It's Upsetting for almost everyone ivolved.

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