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facing a cast iron casting

looks like somone did it with a blunt chisel:-(

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Dismaldunc15/11/2009 16:04:29
91 forum posts
8 photos
Hi Folks, back with my next question! I'm doing ok parallel turning but when I try facing a bit of cast iron (stuart cylinder head) I get lots of chatter? and vibration even though everthing is snug and tight.
the end result is to be blunt (which I dont think my tool is)  poo
 
The lathe is a shiny new chester conquest and I'm using the wee blue tools that come with it (replaceable tip ones on order from RDG)  tried different speeds and feed rates but itsstill not happening for me .. any pointers or advice would be most welcome
JasonB15/11/2009 16:20:36
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25215 forum posts
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It could be that the castings are chilled, heard several comments that this is an increasing problem with Stuart castings. Chilling is when the molten metal cools too quickly and becomes very hard.
 
Try taking a deep cut for your first cut to get under any hard skin, if that still does not work then put the casting into a fire or woodburner for the evening and allow it to cool with the ashes overnight, hopefully this will normalise the iron.
 
Also keep the speed down to say 300rpm assuming its a 10V or H you are working on
 
Jason
wheeltapper15/11/2009 16:50:22
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424 forum posts
98 photos
Hi
I have a Chester Comet and the wee blue tools that came with it are, frankly, crap.
 
I threw mine away and got some hss tools, made a world of difference.
 
my tuppence worth.
 
Roy
JasonB15/11/2009 17:17:41
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25215 forum posts
3105 photos
1 articles
You will need to use a green grit wheel to sharpen the tools that come with it as they are brazed carbide tipped, a normal bench grinder wheel won't get them sharp
 
Jason
Vapeur8915/11/2009 17:37:01
18 forum posts
I have  bench lathe almost like the DB10G from Chester with 1hp motor. To face a large round casting  I use carbide indexable tooI with an 1/2'' shank. There are special grade of carbide inserts for roughing if the metal is a difficult one. As to me I never meet problem with hobbyist inserts.
 
After that  I check  :
* that the tool is not  overhanging too much from the tool post.The less the better
* that the tool is exactly on the lathe axis or slightly under (2 or 3 thou max)
Then
*  I put a slight angle to the tool post (not the compound slide) to be sure that only the tip  of the tool is working and the tool's side is not rubing the casting. That way the cutiing pressure is maximum
* I lock all the movements : cross slide and longitudinal movement  and the compound slide during each cut.
* I take light cuts about 0,4mm  (1/64'')
 
This way I turned 120mm (4 3/4'') casting for a chuk backplate without problem. The speed was around 300 rpm during roughing and 700 rpm for finishing. With cast iron it's a dirty tedious work.
 
If that can help.
Patrick
Dismaldunc15/11/2009 17:55:34
91 forum posts
8 photos
thanks chaps, Think I will await my new tools and see how they perform, thanks for the info Dunc

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