Long Straight Swarf

savarin

savarin

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I was turning down some hot rolled 19mm thick plate to make a 50mm dia puck.
The swarf was coming off in nice curly strands with no problems when suddenly it started throwing off straight unbroken razor sharp strings with no warning.
It was a brazed carbide bit so was flat on top.
I used a diamond stone cutting wheel in the angle grinder to add some rake and a chip breaker into the carbide and tried again.
Better but no cigar. tighter curls, shorter lengths but then suddenly around the centre of the steel long straight arm tearing lengths shooting off. Very very scary.
Any ideas why?
 
When you say “centre of the steel”, is that in regard to diameter or in regard to thickness/length? If regarding diameter, I’d try increasing rpm. If regarding thickness, I’d ask the same question you did and hope that someone smarter than me responded. ;)

Tom
 
Hi Tom, the centre third of the thickness of the original plate, in other words the middle of the two hot rolled sides.
I am assuming its a difference in homogeneity of the steel from the rolling process but maybe its my speeds and feed.
I experimented with these but didnt get much difference except the straight swarf came off slower.
On close inspection they looked like mini band saw blades, teeth on one edge smooth on the other.
 
I have had that problem also with some round stock. The outside turned nicley, but from the center out to about .125 radius it turned into a wire shooter, like a mad mig welder on drugs!
The only thing I could think was that the grain structure fluctuates from the diffrent cooling rates from center out. I ended up having to feed manually so I could stop and break the string off before it became a problem.

Sent from somewhere in East Texas Jake Parker
 
Any plate product in as rolled condition will vary in mechanical properties through the thickness. That's what you are seeing. The less stress the material has seen the more ductile it will be, in the case of carbon steels especially, such as the (likely) A36 you have.
 
savarin said:
I was turning down some hot rolled 19mm thick plate to make a 50mm dia puck.
The swarf was coming off in nice curly strands with no problems when suddenly it started throwing off straight unbroken razor sharp strings with no warning.
It was a brazed carbide bit so was flat on top.
I used a diamond stone cutting wheel in the angle grinder to add some rake and a chip breaker into the carbide and tried again.
Better but no cigar. tighter curls, shorter lengths but then suddenly around the centre of the steel long straight arm tearing lengths shooting off. Very very scary.
Any ideas why?
Click to expand...
Play with the depth of cut, feed rates and spindle speeds, for instance a low DOC or feed rate will tend to create a thin chip that will not easily break, a very high SFM will cause a good deal of heat if run dry this may cause a very soft chip that will also not break, increasing the feed rate and DOC when roughing will often make the material short chip, hit it hard when roughing .100" DOC at minimum and .008 to .015" per revolution or more feed rate on a 2" diameter part, create a thick chip that can't help but break. Also toss the brazed tool and invest in a single insert tool with molded chip breaker for OD roughing operations, then switch back to the brazed tools for finishing if that is what you are comfortable with, roughing is exactly as it sounds knocking as much material off in the shortest amount of time leaving .010 or so for finishing.
 
Welllll ... if you didn't like last year's answer, maybe you'll get a better one this year ... ? ;~)
 
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