Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

I made a pin to fit to the center hole, with the idea of using it to locate the hole and therefore allow me to mill the rails accurately.



Then I started milling the insides of the rails.



After an initial cut, I located the center of the hole again, and took a measurement to the top of the casting surface of the rails, to get a feel for how much I was going to need to remove.



That technique worked well enough, but in the end I actually touched off the bore of the hole with the height gauge rather than using the pin.

Anyway, cleaned up the rails





I made a bit of a meal of this, with multiple set ups I didn't need, if I'd actually thought through it a bit better. I ended up taking the casting out, and turning it sideways to check the inside rail to bore center dimension using my height gauge. I was a bit worried I'd messed up because at this stage the rails were very uneven. However, it turned out I just needed to take more off one rail.

I set it all up again, and finished up.





Then drilled and tapped the upper rail mounting holes.





As far as I can tell, I'm within .001" on the width of the rails, with the centerline of the rails maybe within 0.003" of center line of the bore, and height of the rails is within .001" of nominal, so not a bad go at it.

Got to think about how to do the bearing caps and crankshaft bearing holes now, so I may move on to something else tomorrow while I mull that over.


That brings me all up to date. From now on, I'll be posting as and when I get time to work on the engine - which is never as frequently as I like, and I don't move very fast when I do get the time. Such is life!