Assuming the plate isn't too hard, and it might well be given the heat you mention. Try a file and see if it marks the casting, if it doesn't then there's the problem. Inspect the cutter tips for damage. Good cast iron can be worked with HSS or a single point carbide cutter with lowish power.

The face mill might be too big for both the power available and rigidity of the Rodney, if the plate files try a smaller end mill.

I suspect you have a list of disadvantages adding up to cause trouble. The Rodney and clamping are a bit wobbly, that facing mill is asking a lot of a small motor and – this is the biggy – cast-iron often comes with an extremely hard outer skin. Inside it's easy to cut, but breaking in can be an HSS blunting nightmare!

I'd try attacking the thin top surface with an angle grinder before trying to mill it. You might get away with cleaning off a slice so the cutter only has to deal with a thin edge as it ploughs across the rest, but if you've got the grinder out might as well do the rest.

The hard layer is caused by fast cooling and it's unlikely to be very thick, perhaps less than a mm. Not unknown though for castings to be deliberately or accidentally chilled making the skin much thicker. Once the top layer is gone try again with the Rodney; I'd use a single point flycutter rather than a face-mill because they don't need anything like the same power and rigidity of the milling machine. Give your face mill a try though; soft cast-iron is easy to machine.

If this is your first time with cast-iron beware of the mess! Awful black stuff that goes everywhere. It's worth spreading paper and magnets about and cleaning up as you go. The hard gritty top surface is particularly bad for lathe ways so give it a good clean when you've finished.

Dave

The skin of cast iron can be nothing like the 'real' stuff underneath. The skin can be chilled – forming iron carbide, which is very similar to tungsten carbide, and just as difficult to machine. It has a silvery appearance, whereas the body of the casting is going to be dark grey, with included carbon which rubs off on a finger. This darker material can be machined using old fashioned tools of carbon steel, which is one reason why it was used so much in the 18th and 19th centuries for engineering.

It might be worth trying to remove some of the carbide by heating the casting to redness, and allowing it to cool in the ashes of a fire (such as a barbeque). This slow cooling should help to ensure that some at least of the dead-hard problem material changes back to iron, and carbon. The ashes serve as a blanket and prevent any sudden colling from drafts, etc.

Hope this helps

Tim

I have in the past, used angle grinder to put small 45° angle cut along the edge to be 'hit' first by a carbide single point tool, to break thro the skin. It worked OK.

I wouldn't use a shell mill on such a flimsy set up as Rodney/Myford. No substitute for a proper mill and as hefty a type as possible.

Suggest you join a club with a decent workshop and if needed, a fellow member will advise / teach use of a big mill.

As said above, cook it in the ashes of a hot BBQ. Or solid fuel stove. Leave overnight to cool slowly, buried in hot ash.

Definitely some chilled iron there; PIA unless you can get under the 'skin' or heat treat it as mentioned. The following pic shows the 'chilled' outer O/D portion of the frame off my S10,

George.

1.Although it helps to have a rigid machine these cutters can work on light machines, I exchanged a few Wattsapp messages yesterday with someone happily using a 40mm facemill on a SX1LP. End mill eg 4-flute cutter would be the best of the three options you have but if it is from a similar source to the facemill and inserts then all bets are off.

2. No you need hotter than your oven about 875deg C and it needs to soak right through then cool slowly, On a limp like that I would say you may just have a harder skin not chilled a sthat mostly happens on thin castings and corners/edges very much like George's photo

3. Two videos at the end of this reply first is with the supplied inserts, see how the lamp vibrates, second is with better inserts on the same piece of iron, then steel and then aluminium all cut fine after changing inserts and making sure the head was running concentric to its loose fitting arbor

4. 1000rpm would be about right but I suggested the 500 as a conservative improvement also don't know what Rodney is able to run at.

When it's cutting right you will get small chips not dust so although your belly will be clean it will also get lots of little burn marks

Cost is about quality of the carbide and a keen edge.

Edited By JasonB on 19/07/2019 07:18:05