Making White Metal Bearing Shells Pt.2

Before I finish machined the new bronze shells, I checked the crankcase to see if the holes that they would go into were round (though not necessarily all in line as this can be remedied later). Surprise surprise, they weren’t round. So the next thing to do was machine it all back to true….

With the crankcase mounted on the line borer I could machine each housing in turn. Here I am working on the rear main (flywheel end) on the left hand side of the picture. The red over-arms of the machine support the boring bar which is driven by the blue mechanism on the right hand side of the picture.

Here’s a closer view of the action. The bar has a cutting tool sticking out radially. How far it projects from the centre line of the bar dictates the diameter of the hole that’s machined. The drive head then rotates the bar whilst moving it along its axis until the cutting tool has passed completely through the bearing housing. Easy peasy.

Once the bores were cleaned up I also faced each end back to clean to ensure that they were perpendicular to the bores. Tis ensures that the bronzes will all fit nicely.

Then repeat for the other four main bearings!

Whilst I was at it I thought I’d check the con-rods. Yup, they were out of round too. Here’s one of the rods on our con-rod borer with me setting it up to make sure I’m going to machine it correctly- both parallel to the gudgeon pin but also so that all four rods have the same measurement between the centre of the small and big ends. Not a particularly quick job!

Shazam! With all of the housings now round I can get on with making the new bronzes. But we’ll save that for next time….

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