Must have been pretty well worn, your counterbores look to have disappeared. Sleeves or bigger pistons?

Less than .170 taken out of the ID. Bigger rings.

That's just broken in.... is it she was built with no counterbore or just how it looks on my monitor?

She was built with a counterbore. The counterbore is not so evident in the photo I posted but it is still there on the finished product. I will post something soon.

What is the purpose of a counterbore there? I assume both ends? Thanks.

Just how it looks on my screen - all that shiny clean metal.

Counterbores help by providing a datum for dialing in the boring bar if you are overhauling, and to install pistons with rings in place, a least that's what I have done with them....

Mr. McGinley,

To paraphrase Dave's reply --- Counterboring gives you something to indicate off of, should you ever need to remachine the cylinders. Yes, it's on both ends of each cylinder, because you have to center the boring bar on both ends to make a true cut along the centerline. It also makes it a little easier to stuff the piston, rings, and ring compressor into the bores once you're done.

I hope it isn't a jinx to say this, but SO FAR we have had no reportable personal injuries on this project since I bought Audrey on April 11, 2015. Not only that, but so far nothing has got broke during disassembly. (Knock on wood.)

Once more, I have to thank all the guys (and Boilersmith's Kaitlyn) for an outstanding job. BRAVO.

Thanks both for the great explanation on how the cbore leaves a register for future efforts to true-up the bore.
Here is the 0-4-0 Porter I have been building.

Steam locomotive restoration is never easy, it is certainly not cheap, and you always find more things to fix once you get started. This particular bolt was one of 14 that attaches the cylinders to the frame. This bolt and several other frame bolts have been replaced. How many restored locomotives have been returned to service without someone climbing under the cylinders and carefully inspecting each bolt?

Once more, all I can do is say "Atta Boy" to Tommy and the 30 or so other good folks working on little Audrtey.

And, my apologies to Mr McGinley because somehow I missed the photo of his much more sensibly sized Porter project -- She's a beauty, Sir, and I bet she'll be a steamin demon with that copper boiler. Best of luck to you and your locomotive.

I didn't expect to see a Baldwin Flexible Frame Bolt in use on a Porter.... nice find.

It’s a two-piece bolt for mis-aligned holes. My favorites come pre-stripped for easier over-torquing.

That's a good suggestion, but we didn't think of it before reaming the holes and making new bolts. We're going to have to over torque them the hard way.