When you answer these threads you really dont know if the OP is knowledgable on rebuilding engines and understands clearances and machine shop theory.
You also dont know if he is serious or just jerking around but calling him names such as "stupid" without trying to explain and make him understand only shows how "stupid" the person doing the name calling really is
Many decades ago I did the welding on a boiler feed pump conversion job. The pump in question had about a 12 inch discharge which was the ID of the pipe. The wall thickness was a good 2 inches thick
Pipe welded that thick is not a full bevel, its beveled for a distance than straight up to the edge of the OD of the pipe
The bevel has to be perfect as does the face of the pipe (s)
When its fit the root opening has to be exact as its all going to be x-rayed and there is a lot at stake here. The pump pressure has to overcome drum pressure which is 2500 pounds and id guess that feed pump puts out about 3500 and thats at well over 500 degree feed water temps
The piping to the feed pump was cut with a special lathe type of equipment that also beveled the pipe
We were doing this as we were installing a special type of flange on the suction and discharge lines
In the trucking industry when a rear end spindle is bad instead of changing the entire rear there is a company that specialises in repairing these spindles, what they have is special equipment that cuts the old damaged piece, than they bore out the opening which is part of the axel banjo itself and install a new spindle with the threads all machining
Now when the bore that opening its a shrink fit meaning the new spindle is larger diameter. So they heat the rear end at the opening and put the new part in plus they weld it as an extra precaution.
My point is this machining is very accurately done as its dealing with a few thousands of a inch
If the (and I dont know if he does or doesnt) understand the clearness of piston to wall and the proper finish of a cylinder wall that is needed he might think twice
The two examples I used represent accurate machining but id say not accurate enough for an engine cylinder.
Im wondering if he understands engine rebuilding and tolerances involved