Stuart 10 V casting

Hi people,

I have just started my 10 V and not having machined cast iron before i would like to know what the different colours that have shown through after turning are.

It didn't feel as though i had hit any hard spots.

Cheers, David.

It *looks to me* as if you've not quite got through the hard skin on the left. Small iron castings tend to chill in spots where there's less bulk to hold the heat, and the iron is locally much harder at those points. Where it resists the tool you can get a glossed, rippled finish. Perfect cast iron has a bit of an open 'micro-Aero' texture with tiny graphite-lined surface porosities. In some deeper places you can get concentrations of graphite, and I'm thinking that may have happened to the lower lug shown in your second pic.

But really you need to waggle it about to get different lighting angles to get proper view of the surface.

Looking at the base of my 10V - made more than 20 years back - I don't think I machined it at all, but probably emeried it flat with wet-and-dry and WD40 on my bench drill stage. The flat faces of the bed and the standard, as well as the cylinder of course, are more critical, and you should find you've got enough material there to clear the chilled skin completely.

Edited By Mick B1 on 27/07/2019 21:42:40

I would say the most chilled area is the "half moon" on the outer edge of one of the lugs, all the remainder is slightly chilled or you are not through the skin and the only soft bit is the matt grey circular area on the other lug which may well be where the feed riser was which helped slow the cooling rate and prevent chilling.

Generally the harder it is the more it will shine when cut, the softer it is the more matt the finish will be. This part is a good example where the thin edge would have cooled a lot faster than the rest and resulted in something that could only just be turned with carbide yet the rest was easy to work.

 Even easier to see when it's spinning on the lathe

Edited By JasonB on 28/07/2019 07:33:23

Thanks Mick and Jason. I remember before i cleaned the base up prior to putting it in the lathe that there were two lugs in the same position as the more grey area at one end, that must be where it was poured from.

I had taken off 1 mm from that face so the hard spots can be quite deep on thin castings. All good stuff to know.

Thanks guys, David.

I had similar casting 'chilled' areas when building my S10V. The main area on mine was the standard top flange, took some getting through to finish off, as shown the chilled area on the OD was quite considerable...

George.

Thinking about it, I had very similar on mine also. (Stuart 10V Kit from castings)

I actually didn't go all the way through to it was uniform, I just polished each of the surfaces. I didn't realise it was a difference in the metal structure.

Engine runs ok however, so

Del

I thought it was just the outer skin that may be a problem and once through all would be ok.

I must depend on a lot more variables. Cooling rate, quality of material, thickness of material...

David.

My D10 project is the same way. Lots of chrome in the castings.