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Working with Cast Iron Billets (Grade Selection)

Which cast iron grade is suitable for machining?

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Steve Wan25/11/2010 17:21:09
131 forum posts
3 photos
Hi guys,
 
Need your help here, has anyone tried milling precut cast iron billets in block form rather than those already cast?
 
How does one choose the right grade?
Soft enough for machining, no further treatment.
 
Types of Cast iron available for sale:
BS2789 420/7 600/7, BS1452 Grade 220, 250, 260,
Meehanite, Grey Iron, Spheroidal Graphite Iron, SG Iron and so on.
 
My intention for making table top machine building project.
Could someone share some lights here to help me out this confusion.
 
Thanks inadvance,
 
Steve Wan
 
 
JasonB25/11/2010 17:59:49
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25215 forum posts
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The grade 250 machines easily enough and I think thats Meehanite.
 
Spheroidaal Graphite iron is the same as SG Iron and is not as easy to machine, it's more like steel than iron to work and I get better results using coolant when working with it.
 
Jason
Stub Mandrel25/11/2010 21:11:49
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4318 forum posts
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I have worked block of meehanite. Heat treated, machines beautifully with a gentle hissing noise and produces fine filings. You can machine a satin finish with a round nosed HSS tool. It is resistant to shock and quite strong in tension so good for machine tool slides and components. Here's a lump for College Engineering:
 

And the end result:
 

 
Gray6225/11/2010 21:17:20
1058 forum posts
16 photos
As jason says, SG and Spheroidal Graphite Iron are one in the same and are usually specified for high stress applications such as Model traction Engine crankshafts. This is also called ductile iron and exhibits many of the structural properties of some steels whilst being easier to machine.
 
Grey Iron is best suited to engine cylinder heads and blocks, gears and machine slideways but does not have the ductile strength of SG Iron.
 
White Iron is unalloyed cast iron with low carbon and silicon content such that the structure is hard brittle iron carbide with no free graphite.Very limited in its applicable use as it has a low impact resistance.
 
There are many other grades of cast iron that exhibit differing properties and it really depends on the application as to what type you require. This is also applicable to steel as this also comes in varying grades such as EN1A EN8 EN24 etc etc all with differing properties. Then there is stainless, bronze et al.
 
Maybe DC can put in an article or two covering the different grades of these materials and their application, if this has not been covered already.
Martin W25/11/2010 21:52:56
940 forum posts
30 photos
Neil
 
You say that you worked a block of Meehanite that was 'heat treated'. Did this come heat treated as part of the manufacturing process or did you have to heat treat it to obtain the desired  material characteristic? If so do you have details of the heat treatment process.
 
Regards
 
Martin
KWIL26/11/2010 12:16:05
3681 forum posts
70 photos
I have used CES supplied block cut Meehanite (without any additional heat treatment) for lathe slides and similar, machines a treat as others have said, surface "scaling"apparent on some samples so you need to be sure the lump is big enough to cut these away.
Nicholas Farr26/11/2010 12:54:48
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Hi, I don't know what the term "Meehanite" actualy means, if it just a trade name or a  process. However when I was a college, part of the sylibus included some basic mertallegy. In them days cast Iron was referred to as being grey or white, the white being extremly hard and brittle and difficult to weld. It was used for example for such things as fire grates for its resistance to heat corrosion. Grey cast Iron was however softer and much easyer to weld, but it could also be made to what used to be termed as "mallable cast Iron". This was achieved by cooking it buried in a compond (of which I can't remember the name of or the temperatures involed or for how long a period) which drew out some of the carbon content, but kept the cast Iron properties to a certain extent. This is the process that made it mallable which can be termed "heat Treated". Mallable cast Iron was always easyer to cut and drill ect. So wether "Meehanite" falls into this catogory or not, I don't Know.
 
Regards Nick.
 
P.S. you wil have to forgive any errors or emissions in my post as it was way back in the late 60's early 70's when I learnt this.

Edited By Nicholas Farr on 26/11/2010 12:59:53

Edited By Nicholas Farr on 26/11/2010 13:09:13

Steve Wan26/11/2010 13:14:18
131 forum posts
3 photos
Hi all,
 
Thanks so much! I learnt alot here!
 
I know about College Engineering Supply. I got a raw cast iron-tool makers vise from CES along time ago. Now its serving me well to clamp small jobs after being milled and shaped.
 
But CES don't custom made special order. Hence I need to buy cast iron in blocks (being tempered) and process to my spec. With the guide I have from you guys, thankful it helps...ready to place my order soon.
 
Any suitable cast iron suppliers in the UK other than www.westyorkssteel.com for model making so that I could mail-order?
 
Steve Wan
KWIL26/11/2010 14:06:41
3681 forum posts
70 photos
Steve, CES will cut to your size requirement, it is not just their stock sizes. Give Howard an email  to see what he can do for you.

Edited By KWIL on 26/11/2010 14:07:27

Terryd26/11/2010 14:36:18
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1946 forum posts
179 photos
Hi Steve,
 
to follow on from Kwil,  CES will let you collect any order from the Exhibition at Sandown if you are going.  The entry price is then even better value as there are no delivery charges.
 
Terry
 
ps, my last block from CES was salvaged from my garage fire which burned for around 2 hrs before the fire service controlled it and took 3 days to cool, I think it will be heat treated now
 
T

Edited By Terryd on 26/11/2010 14:39:22

GoCreate26/11/2010 15:09:26
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387 forum posts
119 photos
If my college days serve me correct Meehanite refers to a cast iron made to a closely controlled casting and heat treatment/cooling process to provide high quality fine grain structure and consistant mechanical properties throughout the casting section. I believe the process specifically controls the presipitation of graphite.
The Meehanite process can be applied to many cast iron grades including grey and white cast iron and nodular cast iron.
 
Continuous gr 17 (250) cast iron from many suppliers seems to exhibit meehanite quality but I can't be certain that it is? Anyway, the continuous cast iron I have used turned and milled very easily and the fine grain was very consistant, a joy to work with.
 
After machining and retiring from my workshop my dear wife was reminded of her dad returning from work, he was a coal miner. A suitable trail of news paper sheets was layed to guide me to the kitchen sink, enroute nothing had to be touched, only joking.
 
Nigel
 
 
Geoff Sheppard26/11/2010 15:55:55
80 forum posts
1 photos
If you 'Google' Meehanite you will find a lot of interesting information. I hadn't realised it was a Registered name.
Steve Wan30/11/2010 06:02:44
131 forum posts
3 photos
Hi all thanks a million!
Especially to my good friend and helper from Scotland-Nigel (traction-engine).
 
I shall be contacting CES for more info. of raw billets as you guys mentioned.
Will share my Aciera baby mill design also, its in infancy stage now...building up
layer by layer.
 
Hopefully, David the moderator (editor-incharge) of MEW will show interest in this major project.
 
Steve Wan
PekkaNF30/11/2010 10:54:05
96 forum posts
12 photos
Posted by Steve Wan on 30/11/2010 06:02:44:
...Will share my Aciera baby mill design also, its in infancy stage now...building up
layer by layer.
 
Steve Wan
 Hi, I would love to see the the plan and anything on it published.
 
Is it F1 or F3? One decent F3 slipped trough my fingers just few years ago and I'm still in pain.
 
What scale you have been thinkking of?
 
Hope you'll have a quick start on this one.
 
PekkaNF

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