Shrink fitting a steel bush
 

I posted a mail some 4 weeks ago about freeing up a garden shredder which had seized through lack of maintenance - mine!!

Pressure from the head gardener(!) plus seeing how much a new one would cost has encouraged the DIY approach with heat and brute force enabling removal of the end plate. This allowed access to the grinder wheel and the bolts to take the epicyclic gearbox off the motor.

Because the grinder wheel goes so slowly, just plain steel bushes carry its shaft in the aluminium housing and end plate. These bushes are now running freely, but the end plate one came out with the shaft, so will have to go back into the end plate first.

I guess this will be an interference fit needing heat / freeze.

The question is just how much - I can't do more than -20C for the steel bush, but how much heat will the aluminium end plate casting take?

Thanks for any help.

Shrink fitting a steel bush
 

"Rob Graham" wrote in message
...

I posted a mail some 4 weeks ago about freeing up a garden shredder which
had seized through lack of maintenance - mine!!

Pressure from the head gardener(!) plus seeing how much a new one would
cost has encouraged the DIY approach with heat and brute force enabling
removal of the end plate. This allowed access to the grinder wheel and the
bolts to take the epicyclic gearbox off the motor.

Because the grinder wheel goes so slowly, just plain steel bushes carry its
shaft in the aluminium housing and end plate. These bushes are now running
freely, but the end plate one came out with the shaft, so will have to go
back into the end plate first.

I guess this will be an interference fit needing heat / freeze.

The question is just how much - I can't do more than -20C for the steel
bush, but how much heat will the aluminium end plate casting take?

Thanks for any help.

Just smear it with Loctite high strength retainer and push it in by
squashing in your vice (unless you have a press?)

Andrew

Shrink fitting a steel bush
 

On Friday, 2 September 2016 16:53:37 UTC+1, Rob Graham wrote:
I posted a mail some 4 weeks ago about freeing up a garden shredder which had seized through lack of maintenance - mine!!

Pressure from the head gardener(!) plus seeing how much a new one would cost has encouraged the DIY approach with heat and brute force enabling removal of the end plate. This allowed access to the grinder wheel and the bolts to take the epicyclic gearbox off the motor.

Because the grinder wheel goes so slowly, just plain steel bushes carry its shaft in the aluminium housing and end plate. These bushes are now running freely, but the end plate one came out with the shaft, so will have to go back into the end plate first.

I guess this will be an interference fit needing heat / freeze.

The question is just how much - I can't do more than -20C for the steel bush, but how much heat will the aluminium end plate casting take?

Thanks for any help.

Aluminium expands lots. You probably won't need much heat.
I remember removing the bushes in an aluminium motor cycle gearbox by putting it in the (gas) oven.

Shrink fitting a steel bush
 

On 02/09/2016 16:52, Rob Graham wrote:
I posted a mail some 4 weeks ago about freeing up a garden shredder which had seized through lack of maintenance - mine!!

Pressure from the head gardener(!) plus seeing how much a new one would cost has encouraged the DIY approach with heat and brute force enabling removal of the end plate. This allowed access to the grinder wheel and the bolts to take the epicyclic gearbox off the motor.

Because the grinder wheel goes so slowly, just plain steel bushes carry its shaft in the aluminium housing and end plate. These bushes are now running freely, but the end plate one came out with the shaft, so will have to go back into the end plate first.

I guess this will be an interference fit needing heat / freeze.

The question is just how much - I can't do more than -20C for the steel bush, but how much heat will the aluminium end plate casting take?

Thanks for any help.

http://www.engineeringtoolbox.com/li...ents-d_95.html

:)

Aluminium expands about twice as much as steel.

However, without knowing pretty exact dimensions of the two parts, it's
impossible to say much heat is needed. Once you break the oxide film
down, aluminium is highly reactive so you wouldn't put an oxy torch on
it or anything like that.

I'd try Andrew's method, followed if necessary by that plus moderate
heat (say a hair drier), followed if necessary with a hot air paint
stripper.

Shrink fitting a steel bush
 

On 02/09/2016 16:52, Rob Graham wrote:
I posted a mail some 4 weeks ago about freeing up a garden shredder
which had seized through lack of maintenance - mine!!

Pressure from the head gardener(!) plus seeing how much a new one
would cost has encouraged the DIY approach with heat and brute force
enabling removal of the end plate. This allowed access to the
grinder wheel and the bolts to take the epicyclic gearbox off the
motor.

Because the grinder wheel goes so slowly, just plain steel bushes
carry its shaft in the aluminium housing and end plate. These bushes
are now running freely, but the end plate one came out with the
shaft, so will have to go back into the end plate first.

I guess this will be an interference fit needing heat / freeze.

The question is just how much - I can't do more than -20C for the
steel bush, but how much heat will the aluminium end plate casting
take?

Thanks for any help.



Hot air gun will give enough heat