How much Tolerance needed for bearing inserted into aluminium alloy ?

[firasf1dream]

hello guys,
i hope you all having a good sunday,
i need your help with this, i would like to know please :

1 - how much tolerance is needed to insert a bearing inside an aluminium alloy hole of let's say a 20mm diameter ?
2 - and what is the tolerance needed to insert a column inside a bearing ?
i know that for plastic structure the tolerance needed is more !

[flynfrog]

This depends on the bearing. Most bearing manufactures have fit charts online. If the hole is to tight you can over shrink the outer race of the bearing. If its loose your bearing can come out. For rule of thumb I try to size for a .0003-.0005" fit for 1.5" bearings. Another resource is the machinist handbook.

it will have fit tables for press fits

http://www.amazon.com/Machinerys-Handbo ... 083112900X

[firasf1dream]

This depends on the bearing. Most bearing manufactures have fit charts online. If the hole is to tight you can over shrink the outer race of the bearing. If its loose your bearing can come out. For rule of thumb I try to size for a .0003-.0005" fit for 1.5" bearings. Another resource is the machinist handbook.

it will have fit tables for press fits

http://www.amazon.com/Machinerys-Handbo ... 083112900X

it's this bearing used for front wheel of RC car upright, i am making the mold for the upright then will be made from aluminium alloy but must make the hole in the mold https://www.surinternet.com/epages/box2 ... s/80109800

about rule of thumb why is that ? you mean for the centrifugal force that will be created while rotating around the center of rotation ? and how do you define the 0.0003" ?! is it in the model for CNC right ? would that be eliminated with a laser cutting machine for plexi mold ?

[flynfrog]

you will not be able to cast a good enough hole to press in a bearing I would cast undersized then bore our your bearing areas.

your hole would be .0003-.0005 smaller than your bearing od. This should give a nice removable pressfit

[firasf1dream]

you will not be able to cast a good enough hole to press in a bearing I would cast undersized then bore our your bearing areas.

your hole would be .0003-.0005 then your bearing od. This should give a nice removable pressfit

i did not understand much :/
you said you would mold smaller hole, then bore with what ?
what is od ? what is press fit ? is it done by the bench drill ?

[flynfrog]

you would bore with a boring bar in a mill. You might be able to get away with a drill bit followed by a reamer if the hole is small enough. I wouldn't try it with a drill press they tend not to be stiff enough to get a good bore.

A press fit is like it sounds where your using deformation of the parent matl. to hold your other part in place.

[Tommy Cookers]

1 - how much tolerance is needed to insert a bearing inside an aluminium alloy hole of let's say a 20mm diameter ?
2 - and what is the tolerance needed to insert a column inside a bearing ?
i know that for plastic structure the tolerance needed is more !

you seem to be asking about an interference fit not a tolerance
the interference is the difference between 2 nominal dimensions
(the bearing outside diameter will be larger than the bore (inside diameter of the hole) by the interference)

the tolerance defines the range of actual dimensions of the parts made to the nominal dimensions
the tolerances will be much smaller numerically than the nominal dimensions
if they are not then your interference will probably fail

[firasf1dream]

you would bore with a boring bar in a mill. You might be able to get away with a drill bit followed by a reamer if the hole is small enough. I wouldn't try it with a drill press they tend not to be stiff enough to get a good bore.

A press fit is like it sounds where your using deformation of the parent matl. to hold your other part in place.

ah a mill machine ! yes but isn't the mill machine horizontal ? i mean the axis of rotation of the piece, on google it put the vertical machine, or am i confused with the names ?

about the press you are right, sometimes it tend to move from the right point :/

[firasf1dream]

1 - how much tolerance is needed to insert a bearing inside an aluminium alloy hole of let's say a 20mm diameter ?
2 - and what is the tolerance needed to insert a column inside a bearing ?
i know that for plastic structure the tolerance needed is more !

you seem to be asking about an interference fit not a tolerance
the interference is the difference between 2 nominal dimensions
(the bearing outside diameter will be larger than the bore (inside diameter of the hole) by the interference)

the tolerance defines the range of actual dimensions of the parts made to the nominal dimensions
the tolerances will be much smaller numerically than the nominal dimensions
if they are not then your interference will probably fail

yes i know what tolerance is but can't we use the term for a very small difference between the main diameter and the bore ?

[Greg Locock]

Bear in mind that wheel bearings and spindles get hot under braking and so differential expansion between the steel and the aluminium will cause the bearing to fall out. This may not be an issue with a toy racing car.

[piast9]

ah a mill machine ! yes but isn't the mill machine horizontal ? i mean the axis of rotation of the piece, on google it put the vertical machine, or am i confused with the names ?

There are both horizontal and vertical milling machines.

[firasf1dream]

Bear in mind that wheel bearings and spindles get hot under braking and so differential expansion between the steel and the aluminium will cause the bearing to fall out. This may not be an issue with a toy racing car.

thank you guys
Greg actually this is not a toy, it is a real car but scaled to 1/4 dimensions :/
so what shall be done in this case ? or you are saying that the difference should be very small ?

[Greg Locock]

I suggest that if you want to design it properly then either you build a prototype and fix all the faults, or you design it the other way that real cars are designed, which is not by getting hints off the internet. Big clue - real cars rarely use ball bearings press fitted into aluminium spindles these days. They use these hub units instead http://www.ntn-snr.com/autoaftermarket/ ... ement_roue

[firasf1dream]

I suggest that if you want to design it properly then either you build a prototype and fix all the faults, or you design it the other way that real cars are designed, which is not by getting hints off the internet. Big clue - real cars rarely use ball bearings press fitted into aluminium spindles these days. They use these hub units instead http://www.ntn-snr.com/autoaftermarket/ ... ement_roue

ahhhhh okkk so the bearing are like built into the hub !! yes you are right but for 1/4 sizes we have to make compromise so that is what i am doing, because you can not find such a hub for 1/4 scale so i am trying to find solutions that are acceptable by searching for how nowadays RC cars f1 are made and i found out that my method is right by making an alloy uptight and press 2 bearings in it from each side

[riff_raff]

The tolerance and fit of a steel rolling element bearing into an aluminum bore will depend on the operating conditions, the type of bearing, the precision class of the bearing, and how the bearing is loaded and constrained.

For example, if the bearing has been manufactured with certain amount of internal radial clearance, and it is installed into the housing with sufficient interference at the outer race OD to eliminate the internal radial clearance, it will cause failure of the bearing.