My Stuart 10H Cylinder has a boo boo.

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Well-Known Member
HMEM Supporting Member
Feb 6, 2018
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Central Florida USA
The casting set I purchase four years ago at the Consignment Sales Area of
Cabin Fever Model Engineering Expo Show, It seems that the person who had it before me
tried to bore the cylinder,in doing so the bore is off center. :(

If I were to rebore the cylinder to correct it, it would make the bore about 0.037"/ 0.940mm oversize.
I am looking for recommendations from you real model engineers on here what would you do? 🤔

#1: Bore it over size and machine the piston to fit? or
#2: Bore and sleeve it and keep the piston to the design size?
If so what diameter should I bore it out too, and what size should I make the sleeve?
The cylinder is cast iron.
My vote:

Bore it oversized, and make a piston to fit that size bore.

I don't see any gain in trying to get back to the original bore.

Auto and truck engines are routinely rebored to a new size (or at least they use to be; perhaps not as much now).

If I , I will consider whether increasing the size of the cylinder will have any effect on other parts? 1 or 2 mm - probably no effect (see your engine plan)
If everything is okay then : Bore it oversized, and make a piston to fit that bore size
That Is the best solution
Try the overbore first but be aware that you may come close to the cored steam passages. If you do hit them then sleeve it.

Alternative is to look closely at the outer dmensions as it may be possible to leave the bore as it is and true the end flanges to the bore and if the port face is not right then make adjustments to valve chest etc to cure that. This is a bit like scratch building cylinders from the solid, I put the bore in first and then shape everything relative to the bore.
OR, a new cylinder casting from Stuart Models is pretty cheap !!!
Well it took a while to dial it in on the four jaw, 🥴 but we have a winner.🙃
The cylinder was saved, all is good again in the shop. 👍

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