How Much Cast Iron Do You Need To Peel Off Of Virgin Metal

Baithog

Baithog

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I have a rectangular piece of durabar that I am squaring up. The bar, as received, has 2 rows of marks on the side. I machined .25" off one of the pieces with an end mill. Those marks were still there and some looked like they had little cracks in the marks. I took off another .25" and the cracks went away, but the marks became dark smudges. I took off .002 with a fly cutter to get rid of the end mill pattern, but the marks are still there as dark smudges. Do IMG_1189[1].JPG IMG_1188[1].JPG I need to mill off more to get rid of all of the smudges before I make something of the bar? Does anyone have experience with durabar? How much do I need to take off?
 
Simple answer: it depends. What are you making?

Not knowing, I would probably remove metal until the finish appeared uniform and free of stresses.
 
Baithog said:
I have a rectangular piece of durabar that I am squaring up. The bar, as received, has 2 rows of marks on the side. I machined .25" off one of the pieces with an end mill. Those marks were still there and some looked like they had little cracks in the marks. I took off another .25" and the cracks went away, but the marks became dark smudges. I took off .002 with a fly cutter to get rid of the end mill pattern, but the marks are still there as dark smudges. Do View attachment 123422 View attachment 123423 I need to mill off more to get rid of all of the smudges before I make something of the bar? Does anyone have experience with durabar? How much do I need to take off?
Click to expand...
Speedy Metals says that their Durabar-lookalike should finish at .25" under nominal. If you still see defects after taking more than .25" off one side you might want to consider contacting the vendor.
 
I vote for 'it depends'. And then you could mill half of it and still find a defect. I say work around
the defect We just don't know what you are doing or put into stock???
 
The cast iron from Speedy Metals is Durabar. It is printed right on the metal. I found the durabar site. They claim to be way superior to other continuous cast stock. I have seen good reports about Durabar so I'm happy to find that Speedy metals is selling it. There is a defect under almost every mark. I am guessing that it is from whatever machine they handle the bar with as it is cast. Probably nucleation sites for stress, so I'll keep milling. I have taken off .052" of stock so far. That leaves .073" per side more to get to the 1/4" that the bar is over size. So now I just have to figure out where to stop roughing and stress relieve before taking the last off. I haven't been able to find any recommendations for where to stop roughing and start finishing.

I am making a straight edge, way extension, and gibs.
 
Baithog said:
The cast iron from Speedy Metals is Durabar. It is printed right on the metal. I found the durabar site. They claim to be way superior to other continuous cast stock. I have seen good reports about Durabar so I'm happy to find that Speedy metals is selling it. There is a defect under almost every mark. I am guessing that it is from whatever machine they handle the bar with as it is cast. Probably nucleation sites for stress, so I'll keep milling. I have taken off .052" of stock so far. That leaves .073" per side more to get to the 1/4" that the bar is over size. So now I just have to figure out where to stop roughing and stress relieve before taking the last off. I haven't been able to find any recommendations for where to stop roughing and start finishing.

I am making a straight edge, way extension, and gibs.
Click to expand...
Ok. The Speedy Metals site says nothing about Durabar and the piece of continuous cast I have from them is not labeled so I assumed it was a look-alike. The surface marks are probably from the mechanism that pulls the bar through the die it is cast in. My piece has them as well but they are just superficial. In any case you shouldn't need to go that deep to get to good metal.
 
I've been involved with the use of DuraBar products for nearly 35 years. Mostly with bar and tubes. And the way it was explained to me, if the stock size was 2" x 4" actual physical size can be up to 3/8" plus oversized. This varies according to the size. 26" OD bar is close to 1" bigger on the OD. It is guaranteed to clean up to the stock size specified if done correctly. I've never see or heard of anyone complain. You also have to remember that DuraBar has a "skin" to it. You have to get under this skin in order to get to the "good" iron. There are impurities, surface cracks, etc., in the skin.
 
Fat finger error. I made 2 passes with a 1/2" end mill at 0.025 per pass, then 0.002 with a fly cutter. Total metal removed was 0.052". I can take off another 0.070" and still be on size. I wanted to know if the discolorations that I see are stress defects and if they will be gone when I reach nominal size. And yes, I would like to take off as little metal as possible. Sorry for the confusion.
 
Making a straight edge I can see why you'd be a bit paranoid about defects but with cast iron, even Durabar, I wouldn't even bother looking for them until I'd taken off .100".
 
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