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The rings are about 1/8" wide and 1/16" thick. They were supplied with the castings and there was no issues stretching them over the piston. They are probably overkill for a model but it's nice to put them to use after they have been so patiently sitting in their box for so many decades.

Part 9 - Making the Piston First job was to clean up the casting. Despite what the plans specified I decided not to rely on the thread for alignment and machined a small rebate into the piston. This will be a tight fit against the piston rod. Now that the piston is cleaned up it was time to...

It's as parallel as I can measure, and it's bang on 0.5"

Lots of people swear by those little honing tools that are made for car brake cylinders. Personally I don't really trust them so I always make my own lapping tool. Even if a lapping tool is not perfectly cylindrical it will tend to become so with use and my results so far have always been very...

Part 8 - Cylinder End Caps Next I decided to tackle the cylinder end caps. The Tubal Caine book rates this as such a simple job that it doesn't bother to provide any guidance. Personally I found it to be quite an interesting challenge. My main concerns were to ensure that the end caps were...

The No.2 Mill engine is also very nice. It looks quite ugly on their website but mine turned out very nice.

It seems to break down very quickly but I am very careful to put down some paper towels to protect my ways. It's quite similar to corundum. I also always have a piece of leather on the front of my carriage to protect the ways from swarf.

Oh I see. I completely misunderstood that comment. There surface of the bore is very smooth. I think the piston rings will make it even smoother once the engine is completed. It came with some very lovely piston rings and I think it would be a shame not to use them.

I was leaning towards the tangential shape but your examples are pure perfection. Now I will have to revisit the idea of using the boring head. There is no option of leaving the boss as cast because it does not fit within the mating part. In the Tubal Cain book on the engine, he simply...

It would be very difficult to cut a 30 degree spiral for the lapping grooves. I would be very surprised if it made enough difference to warrant the effort. The diamond paste I used is marked as 40 micron.

Part 7 - Cylinder Lapping My next task was to build a tool to lap the cylinder bore to make sure it was smooth and straight. I have built tapered laps before and learned that a good design will include the following features: Threads at both ends so the expanding part can be pushed in either...

Thankyou both for very long detailed and interesting replies. I am not overly concerned with my surface finish at this stage as I was always intending to build an expanding lap. The construction of this is progressing nicely and will feature in the next update. The design is similar to the...

This video shows the speed etc of the setup used on the mill.

Well it turns out that my boring bar is actually a genuine Myford accessory most likely purchased by my lathe's original owner. I bet I am the first person who has ever used it! I won't give up on it just yet. It's poor performance must have been user error.

Part 6 - Boring the Cylinder After the usual fettling I started out by cleaning up the casting in the milling machine to give myself some good reference surfaces to work from. I started by milling the port face. Once that was done I used my grinding vise to clean up the ends. I did this...

Part 5 - Reverse Counterbore The back side of the cylinder flange is very curved and I wanted to make sure that the nuts that hold things down have a flat surface to press against. I could not use a normal counterbore because the bearing journals are in the way so I needed to make a reverse...

I once was so annoyed that I couldn’t find the cap for my tube of lanolin that I made my own cap. Of course I found the original cap the next day.

I once used mine to repair my pool pump. The pipe needed to be replaced in this fitting which wasn’t available as a spare part. I bored out the old pipe and it worked great.

Thanks very much for that tip. I have been worried about that forever. It seems like a crazy design. Especially if you consider the steam chest would most likely have a gasket. Problems seem to be inevitable.

It's especially tricky to do the bearings first as pretty much every feature on the engine is dimensioned from the cylinder flange. It's hard enough to decipher the expertly hidden dimensions on this drawing without having to work backwards! If it was good enough for Tubal Cain, it should be...