Model Engineering

Once cleaned up by filing, the flywheel can usefully be mounted using the outside of the jaws in the three jaw chuck, and was fairly centrally aligned.  This allows for gently tidying up all the accessible edges of the casting and sizing the hole for the crank shaft.

With that done, I mounted the flywheel on a scrap piece of 9/32 stock to perform the rest of the turning – hopefully that will ensure it’s nicely concentric when mounted on the engine.  With only the setscrew holding it in place gentle cuts are the order of the day, and I’m using my new (to me, anyway) live centre to add support and prevent chatter.

Flywheel in position – starting to look like something now !

Moving on !  Turning the piston to fit neatly into the bored head of the cylinder:

And using the chucking piece to turn the crosshead down to fit into the standard:

Tapping the crosshead for the piston connecting rod – started by supporting with the tailstock to get it concentric, although you can’t see that here:

Using the corresponding die to cut the thread on the piston connecting rod – my pratt burnerd chuck is adequately accurate for this – alternatively a bush to hold the rod could have been made from scrap brass.

Completed assembly – I’ve followed the advice from the Pengwern book – cutting one fairly deep groove in the piston for graphited packing rather than 3 finer oil grooves.

Second time lucky ! I’ve tidied up the valve chest cover casting with some micromesh – although I expect I’ll paint it eventually.

Progress so far…

Top and bottom cylinder covers completed. Fairly simple with a bit of cut-and-try to get a nice fit in the cylinder. I used the parting tool to make the top cover in one operation.

Assembly so far.  I’ve also drilled, tapped and installed the studs to hold the soleplate to the boxbed.

Initial setup of the valve chest in the 4-jaw, using parallels to hold work clear of the jaws.

Top and bottom facing done, remounted with soft jaws to clean up the sides of the casting.

Turning completed – part now marked out in preparation for drilling clearance holes for mounting bolts.  In doing so I noticed one centre pop needed ‘drawing’ over slightly, so one more tap and……

Starting to reduce diameter for the bottom cover. The notes I have imply that the supplied stock is 35mm ground cast iron – the material I have isn’t ground so needs a bit of tidying up.

Different view of the same job.

Using the Warco digital scale to cut the shoulder down to the correct depth.

Once the spigot had been drilled and a 5/16th thread cut the parting tool came out.

Then the part was reversed, mounted in the 3-Jaw and the spigot / rebate (?) cut to ensure a nice fit in the cylinder.  I’ve reamed the hole out to 4mm to use 4mm silver steel as I don’t have a 5/32” reamer.

Cylinder faced and being bored out to 19mm.

I did think about lapping the bore – maybe before I make the piston.

With the feet machined flat some modified clamps were used to hold the standard on the faceplate.

Clocking the outside edge of the standard – bit fiddly with lots of re-mounting of the faceplate.

Turning and facing the top of the standard is pretty straightforward – Lots of light cuts meant boring took a while.

More filework in the vice – I used needle files to get everything looking good before machining.

Same for the standard – I cleaned off the lumps, presumably where the metal was poured into the mould.

Fairly odd setup for the machining the feet.  I was half expecting bits of casting to fly around the workshop, but it seemed to be rigid enough to machine.  I popped a washer over the point of the centre in the tailstock to stop it digging too far into the dowel.

Just a closer look at the setup after a couple of passes.

Just a closer look at the setup after a couple of passes.

First steps – clean the boxbed up with a Dremel and a file to get rid of any casting flash.

Mount in the 4-jaw. I’m using brass sheet to protect the casting.  Doesn’t have to be super concentric, as long as it’s fairly well balanced.

Facing off – I’m using a tipped tool here and 320 RPM.  Seems alright to me !  I cut .20mm at a time, with a .10mm finishing cut.

Once faced, flip over in the chuck, ensure it’s seated nicely, and face the top.

Quick check with the height gauge.