I would not choose PB ,a lump of cast bronze(gun Metal) would be more suitable and a lot easier to machine

Alan,

Bit of a difficult question as there are many ways to 'skin a cat', all depends on machinery available and the tooling you have to go in it. I am currently machining the cylinder for a 6" Savage, a casting (iron) and rather bigger but the principles are the same I would say. My plan of attack has been to mount the casting on the table of my mill (it has horizontal and vertical spindles) so at one setting I was able to machine the top face and the steam chest face. Translating that to your lump of bronze if you machine two flats at 90 degrees you then have datum faces to step off for the bore and the saddle radius and two flat surfaces for clamping. My current stage is now mounting it on a horizontal borer to machine the bore for the cylinder liner and then I can use the coordinate scales on the machine to step off to the centre of the saddle radius and machine that. I will then return it to the mill to machine the valve face, drill off the ports and the stud holes for the end covers and saddle.

Couple of things to consider – when you do the saddle radius you want to consider not only the diameter of the boiler but the thickness of any joint you may intend to use between the boiler and the cylinder. When you drill the stud holes in the flange make them a reasonable clearance – as you pull down on the joint any compression will result in slight movement at the extremities of the saddle. Too tight a clearance on the holes and the studs may bind and the joint may not seal.

I guess you don't have a horizontal borer but it can all be done on the mill as yours is quite a small cylinder, would help if you have a boring and facing head for the spindle though (rather than just a boring head). You can do it without but the facing function makes life a bit easier.

Paul.

On the Minnie a rough hole is put through the block and this is used to mount the cylinder onto the faceplate so the underside can be machined to the required radius. A piece of bar is then used as a dummy boiler to mount the cylinder between ctrs so the top of the saddle can be done at either end turning the lathe by hand due to the imbalance. A couple of screws up into what will become the cavity at the bottom of the cylinder can be tapped for fixings.

You could also do similar with a rotary table on the mill using a vertically mounted "boiler" to fix the cylinder to for milling the ends and then mount horizontally for the top of the saddle along the sides.

Alan,

A bit difficult for me to visualise how leaving it on the faceplate to transfer to the mill will help. I would have thought it may restrict access to get the cutter in to where you need it especially if you are holding the cutter in some kind of chuck (auto lock, ER etc). Only you can really know what you have in mind and where you need to machine. Jason's idea of a 'dummy boiler' on the rotary table sounds a reasonable plan especially if you can mount your table both flat and vertical, that should allow you to rotate the block wherever you need it.

I am a time served fitter / turner from many years ago but haven't worked as a machinist professionally for years, all my hands on machining is on my own kit in my own time! I tend to go my 'own way' in terms of setting stuff up and machining sequences. All I can advise is spend a bit of time thinking through every stage of the job from start to finish according to the facilities you have available and then work through your mental plan bit by bit. Don't be afraid to think out of the box or be unconventional!

Paul.