Gentlemen
I am not a machinist but I can read machining texts and I am still having great difficulty in turning or milling for that matter any steals harder than mild steel. My latest project requires turning a 1 1/2 " bar stock. It is 4140 half hard stock purchased from Enco.
I am using an 11" Logan lath running at a speed of 380 RPM. I also tried
270 RPM. No difference. I have tried carbide insert tool bits for truing up the end of the saw cut shaft. In doing that, I get down about 3/16" very smoothly and then the metal has a hard layer which just wears my cutter to S#&t in no time or just chips it. I have also tried a cobalt parting tool and that just barely scratchs the surface.I purchased the 4140 because it was advertised as a steel that could be machined and then used without heat treatment.
I am not using any coolant and the type of carbide insert and cobalt alloy is not known. How important are these tool bit specifications and how important is it to have coolant. The text seam to imply that I could cut, what thyey call low carbon alloy steel, with a high speed steel bit and no coolant. Is this true?
What else can I be doing wrong. This seams to happen to me every time I try cutting anything harder than 1020 steel.
John Roncallo