Unable to get a smooth finish in turning mild steel

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compact8

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I have tried many kinds of inserts and different cutting speed but still unable to get a good finish on mild steel. Achieving it on stainless steel , brass and aluminium is super easy. I can get a better finish on mild steel by using sharper inserts designed for fine cutting but the result is still poorer than that obtained on other metals. May I know if there are things that I have missed ? The picture below shows the typical finish I get . With the same insert, the finish on stainless steel is close to mirror like.

finish mild steel.jpg
 
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In all honesty i am probably much less knowledgeable about this stuff so take what i say more like a question then an answer please.....

Could it be possible that your cutting tool is set a bit to high? From your picture it looks alot like that metal is Gauling and tearing caused by the tool rubbing more then cutting.
 
Latinrascalrg1 said:
In all honesty i am probably much less knowledgeable about this stuff so take what i say more like a question then an answer please.....

Could it be possible that your cutting tool is set a bit to high? From your picture it looks alot like that metal is Gauling and tearing caused by the tool rubbing more then cutting.
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No. As spoken the same cutting tool used on stainless steel produces mirror-like finish. I believe the insert is designed for high-load cutting as the tip feels a bit blunt. I have tried using inserts with tips that feel sharper and the result is better but still I cannot get shiny finish.
 
Stone a little radius on the tip, just enough to take the sharpness out of the tool. You'll need a diamond hone if your using carbide.
 
Are you using a cutting oil? I like Tap Magic, a little dab on finish cuts makes a big difference. Mild steel does not finish as nicely as we would like, likely you will never see tha hoped for mirror finish without some filing and polishing, cold rolled is bad enough, hot rolled much worse.
 
benmychree said:
Are you using a cutting oil? I like Tap Magic, a little dab on finish cuts makes a big difference. Mild steel does not finish as nicely as we would like, likely you will never see tha hoped for mirror finish without some filing and polishing, cold rolled is bad enough, hot rolled much worse.
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Yes, high-quality cutting oil is used. I have the feeling that this is just the characteristics of mild steel but I have never get any experienced machinist to confirm it.
 
Your suspicions are confirmed, I can boast of about 55 years of dealing with it, not counting school days.
 
There are many kinds of mild steel. One of them, 1018, finishes poorly like the pic. Your best bet with that material is HSS tooling.
 
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