Gallery, Projects and General > How do I??

Engine question.... bore finish.

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John Hill:
I am making my little air/steam engine and I have a piston that is a slide fit in the cylinder bore.  The piston is smooth and somewhat polished (because that was easy to do) but the cylinder is straight from the lathe and not exactly rough but not smooth and shiney either.

My inclination is to leave the bore as is for better oil holding. However if smooth on smooth is better I will need to remake the cylinder (no big deal) undersize a little and polish it out somehow.

John Rudd:
I thought the usual way was to make a lap tool for both piston and cylinder?

Using lapping compound to achieve the desired finish....

John Hill:
Err, what does a 'lap tool' look like? 

Darren:
Bit of dowel with some grinding paste,

Or soft metal, plastic etc, make it a close fit.... :thumbup:

kvom:
If the engine works as-is, leave it alone.  No one can see the piston or cylinder anyway.

What I have done the past few times is turn the piston to a tight fit and then use it as a lap with toothpaste as the lapping compound.

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