Model A - this is getting boring

 While we wait for the long series drills with which we can finally fit the kickstart pawl, we can look at preparing to drill out for the layshaft bush and for the relief drilling that will clear the layshaft first gear pinion. I need to do some measuring to ensure I understand the various dimensions that will be required, but I know that the bore to clear the pinion will be in the region of 1" diameter.

You will recall that in a previous post we machined off the flange that had been used to hold the shaft in the rotary table, reducing it until it would pass through the fixed steady. We see it in use in the picture below during setup:

The short 5 mm hole that has been used for the revolving centre is opened out progressively until we run out of twist drills. This is the 10 mm drill passing right through and into the body of the shaft:

And here it is opened out to 7/8", which is the largest drill I possess - it actually has an MT2 taper and fits directly in the tailstock:

The next job is to part off the stub, but sometimes it is easier to rethink your approach to a job. I set the lathe up to part off this stub after I moved the fixed steady to the 1 1/8" section, but actually I realised it would be much easier to saw it off:

That took less time than setting up. The orange dust is from the saw blade!

This rudimentary sketch shows us what the dimensions of the hole need to accommodate. As I have no wish to bore the hole to over 1" all the way into the shaft, reducing the wall thickness just where it needs to be strongest, I will make a stepped bush to accept the layshaft and provide a thrust face for the low gear pinion. This will be 1" or thereabouts at the inboard end, and reduce to 7/8" for most of it's length. This will give a thin wall over most of the length of the bush since the shaft is about 11/16".

That's the bore done for the low gear pinion - it's 1.010".

And it fits beautifully:

Now we need the bush, but before we make that the package from Tracy Tools has arrived with the long series drills we need to fit the kickstart pawl and it's pin but before we do that we'll spend the day driving one of these: