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Machining cast iron

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Cadillac

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Have a little project I’m working on. Looking to make a solid tool post mount for my 14x40 lathe. Researching I’ve found the recommended material would be cast iron. I have some suitcase weights off some old tractors 3” thick. Perfect sizes for what I need. Well I marked what I needed and went to the bandsaw. 3A6EEF6C-B21B-47A2-ACE3-D97B86651D9A.jpeg
3B921B2D-DD8C-46E2-9CA9-CEA13A04A479.jpeg
Wow that took awhile probably a hour. It seemed to dull the blade about 3/4 through it. I went and grabbed a portaband and it cut for awhile then seemed to just rub. But I got ito_O
So now to the machining. Figured I’d drill the center hole then use that to align to rotary table and go at it. Drilling the hole was not a problem. Mounted to RT and put a new 1” ruffer end mill 3” long in a 1” toolholder. Running about 135 rpm It made marks in the cast but wasn’t cutting more rubbing and pressure than I liked. So I threw a 3/4 carbide ruffer 1 1/2 long bump the speed to around 250 and it cuts a little better but man this will take a week.
image.jpg
Feels like a lot of pressure to achieve this.
So my question is how would you all go about this?Set up and tooling?
My plan was to ruff out on RT get it round. Then I was gonna put on lathe to cut all the base features. Bring it back to the mill and square out the upper half where the qctp will be mounted. Was thinking of tapering the top area which will be square and transition to the round base that mounts to cross slide. I’m thinking I need to ruff cut more material off before I start machining but the bandsaw blades don’t seem to like it. Any help is much appreciated.
 

BaronJ

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Hi Cadillac,

Cast iron can be a pig, pun not intended, and tractor weights are notorious for having hard spots, very hard spots. I'll bet that the tough to machine parts are where the slots in the casting were ! What happens is that it cools unevenly and chills.

There are two ways that you can deal with this, one try turning it down on the lathe using carbide, two throw it into a forge or furnace get it red hot and let it cool over night, even this might not temper it enough. So you might have to cook it for some hours and then let it cool slowly. Covering it under a pile of sand will slow the cooling.

After this it might be soft enough to machine as you want.
Good luck.
 

silence dogood

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I had the same problem as yours except that I used old window sash weights. When the iron was cast it was cooled quickly so it formed a white cast iron. No one cared since they would be used as weights and no need to machine. Cast iron should be cooled slowly if it is to be machined. In my case I used a side grinder and shaped it by hand since the dimensions were not critical.
 

bill70j

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So my question is how would you all go about this?Set up and tooling?
Cadillac:

Not sure about the machining, but if you still have material to nibble away at, a reciprocating saw with this blade may work well for you. I used it and found it to be fast cutting and long lasting on the thick cast iron drill press table I recently hacked up.

Bill
 

BaronJ

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Hi Bill, Guys,

I bet that drill press table didn't have any hard spots in it. I've seen chilled cast iron eat carbide toolbits !
Yes if you have a relatively small area of chill an angle grinder would help, but its very messy, worse than turning, for dust particles.
 

bill70j

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Hi Bill, Guys,

I bet that drill press table didn't have any hard spots in it. I've seen chilled cast iron eat carbide toolbits !
Yes if you have a relatively small area of chill an angle grinder would help, but its very messy, worse than turning, for dust particles.
You are right. I was expecting the hard spots, but didn't run across any. Not like when I tried to turn a 10# Weider weight once upon a time.
 

Cadillac

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So your saying I should throw it in the fire pit tonight and leave there till morning. I've got a pile to burn and I could bury it in the ash as the night goes. Worth a shot I guess what can it hurt?
 

Bob Korves

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So your saying I should throw it in the fire pit tonight and leave there till morning. I've got a pile to burn and I could bury it in the ash as the night goes. Worth a shot I guess what can it hurt?
That will probably anneal the iron.
 

BaronJ

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So your saying I should throw it in the fire pit tonight and leave there till morning. I've got a pile to burn and I could bury it in the ash as the night goes. Worth a shot I guess what can it hurt?
Hi Cadillac, Yes that is exactly what I am saying !
Bob is right, it will probably anneal the iron, but its not guaranteed to. It needs to get at the least, red hot all the way through. An hour or so in a blacksmiths forge would do it and then it has to be cooled very slowly, which is why I suggested burying it in sand to slow the cooling down as much as possible.

I hope that your fire pit will get hot enough and have enough material in it to slow the cooling down.
 

rwm

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#10
Use a squirrel cage blower and some 2" heavy pipe to blow air into the base of the fire. That will easily get hot enough. I break up aluminum wheels that way. After an hour pull out the iron and immediately bury in in dry sand.
Robert
 
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