A Stuart Williamson build

[Jasonb]

With luck that is only in the chucking spigot.

I'm not a big fan of turning flywheels by holding the hub or mounting on an arbour as it increases the risk of chatter.

See if you can hold by the inside of the rim with the 3 or 4-jaw chuck which will mean you don't need that chucking spigot.

To be safe drill undersize and then bore to the required hole size as a boring bar won't get pushe doff line like a drill and then a reamer would.

[Sanjay F]

The, flywheel, 1st  part of many has been machined after a good soak in rust remover; luckily the hole in the casting was removed during the process

[crueby]

That looks MUCH better!

[Sanjay F]

Thanks Chris

Question:

How do I turn the crank between centres? Shame there's no photo as it says the shaft is turned down to 1/4" using this method, but I'm not seeing how the lathe dog fixes to the web part or maybe it doesn't? Also in the text it says 'turn up your headstock softcentre true'  - what's that?

OR

do I move the lathe dog along the shaft to different positions as I turn it down?

[Jo]

That lathe dog is rather too big  You can mount up a faceplate on the nose of your lathe and add a bolt through the face plate to drive the crank web.

Centres: normally the centre in the tailstock is hard (or a rotating centre) and you turn up a soft one in the headstock, so the driven centre is true. On cheaper quality lathes in the old days turning up a centre might have been necessary but (unless the lathe is really bad) you can use a centre in the headstock.

Jo

[Sanjay F]

Ah........got it! The bolt is in contact with the crankweb part and rotating it; I've been puzzling over that for ages .......thank you!

I'm going to dig out the quick set Keats to drill/machine the offset hole ..... so shouldn't need to make a jig

[Jasonb]

For jobs like this you can make a drive ctr. Your faceplate and spindle nose are too big to use that to take a drive pin a sthe crank is quite small.

Take a bar end of say 25mm steel, face and then tap a M3 or M4 hole in the end.

Back into the lathe to turn a 60deg piont on the end. Don't remove from chuck until crank is complete so the point stays true.

You pop a cap head screw or threaded pin into the hole and use that to drive the crank by the side of the web.

This will allow you to turn the shaft diameter and the inner face of the web. Then reverse in the chuck to face the other side of the web. Move chuck to mill and do the crankpin hole. With the hole now in the web you have something to clock true in teh jig or keats

Smaller version of the second image

[Sanjay F]

I've just tried the big centre/faceplate combo before your post and was left scratching my head 

Let me try your suggestion, thanks

[Jasonb]

what size is the rough cast web, I'll draw it and make sure the 25mm bar is going to work.

[Jasonb]

Thinking about it there is no reason why you can't just hold by the edges of the web in the 4-jaw chuck to tirn the shaft to diameter with the far end supported by the tailstock ctr.

This would avoid leaving a ctr drill hole in the end of the crankshaft at the web end

[Sanjay F]

I did wonder about the 4-jaw method myself but wondered if I'd be able to get it set true - would be a lot easier, for sure. Here are the dimensions and a bit of scrap I found which may work

[Jasonb]

It would have been a bit tight with 25mm but if you put the threaded hole 5/8" from the middle of that piece of bar you have it will be fine as shown attached. 5BA thread would do if you don't have metric.

[Sanjay F]

I have managed to set it up in the 4 jaw and dial it in ........

[Sanjay F]

That worked.....phew! Part 1: shaft to diameter and the inner face trimmed, now part 2 with the Keats

[Jasonb]

Not critical but the face should have been cut to leave the 1/32 thickness at 1/2" diameter. I would also have been tempted to take a very light cut to remove any solder residue as that 1/2" face runs against the side of the bearings.