The fit between the two was of interest during the construction, thanks to historic records of a constant stream of issues about the frame, frame extension, and cylinder saddle working loose. O'Connor did one up on Rogers and CPRR by heat expanding the frame and shrinking it to fit on the saddle. It's lasted in very light service for 40 years - who knows how much longer it would have lasted if they had been hauling trains every day instead of being exceptionally beautiful light demonstration pieces?

If you're going to build new, build new better and it will pay (cost less and run more between failures) in the long run.

Greetings:
Each tapered bolt must be individually fitted to it's hole before being driven into place. Typically, when the bolt is placed in it's hole, the bottom of the bolt head is about 3/4 inch from the surface of whatever it is holding together. Then the bolt is driven into place with a sledge hammer. The bottom of the bolt head ought to touch the surface of whatever it is holding together. Then the nut is applied and tightened. No washer is used, especially not lock washers.

When I was at Tang Shan Locomotive & Rolling Stock Works as the Valley Railroad's inspector during the construction of SY1647M in 1989, there were two young men with wheelbarrows who did nothing but haul tapered bolts from the bolt shop at the end of the erecting hall to the locomotive being assembled by the frame gang. If a bolt was too large, they would take it back to the young women who turned the bolts, individually, on engine lathes with taper attachments. One of them would turn down the bolt a bit and back it would go to the frame gang. Bolts that were a bit too small would soon find a home as the gang reamed holes with tapered, frame reamers and were experienced at knowing just how much to open up the holes. Interestingly, when you calculate the metric taper into inches, it comes out to 1/16th inch in 12 inches, exactly the same as what is used in the USA, Canada and Mexico...

See "American Machinist Handbook", Seventh Edition, Page 1181 for "Taper Fits Used In Railroad Work" for more about tapered fits.
Be well,
J.David

Thanks for that reference. I found a downloadable copy of the 1945 eighth edition available at archive.org. The whole chapter on "Railroad Shop Data," pages 1166-1192, has a wealth of information. https://archive.org/details/in.ernet.dl ... page/n1367

Just be aware that the pdf with text book is a 2Gbyte download and takes a while...

This video on the construction of the 119 and Jupiter may be of interest here. The Leviathan and the No. 17 would be quite similar to these.

And Bill Purdie is in here, too.

https://www.youtube.com/watch?v=oM2A2NEaRqg