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Mill Feed Rate Question

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  • Mill Feed Rate Question

    Got my HF mill (1 1/2 hp) up and running and promptly smoked an American 4 flute TIN coated hss 3/8" tool.

    Old machinery handbook no help.

    I can figure the rpm and inches of feed per minute but what about the amount of cut per pass? First project making an end wrench out of 1/8" mild steel.


  • #2

    I don't know exactly what that mill is.

    You should be able to take 1/16" cut at about 500 rpm. You should be feeding hard enough to make a real chip.

    If you are making "dust" you're wearing the tool out.

    Some soluable oil coolant, or other oil will help if it is handy.

    That's a starting point for you.
    You can work up, or down from there.

    If you're making blue chips, it's running too hot. Gold chips are cool.



    • #3

      Here's a chart with SFM & chip load per tooth. Similar charts are in the J&L Industrial Catalog:

      Barry Milton
      Barry Milton


      • #4
        Good advice all. My students often waste a lot of cutters because they neglect to consider that no coolant is used, or the cutter is somewhat less than razor sharp. I tell them that the charts are set for optimum conditions. No coolant; back off the rpm. Less than real sharp; back off the rpm. What previous posts said about chip thickness is very true. Cutters need to make chips, not dust. Slow the RPM down and feed it "enough" to make chips. Just because a cutter is TiN coated, doesn't mean it HAS to run at break-neck RPM's. Slow down and they last longer. (Remember that slowing down doesn't mean slowing the FEED down to a point of making "dust"). Good luck. Have fun
        Eastern Maine, USA


        • #5
          If the tool dosen't glow cherry red your not running fast enough. 8-) Just kidding. The previous posts are all good advice. But heres some more. You'll brun up some tooling, you'll break some tooling, and after you have a small bin full of wasted cutters you'll have developed your knoledge to where your tooling will last much longer. And if you ever get to the point where you never break or chip a tool and always get maximum life from your tools then write down all that you have learned so I can bennifit from it.


          • #6
            First four flutes are for profile cuts. Sounds like you may need two flute for slotting. I calculated 950 RPM. That would be 90 SFM. Text book calculation. Experience would say 700 would be better. Mild steel becomes very ductile in the shear zone from heat generated. A little coolant or oil will help prevent heat from flowing throught the shear zone and into workpiece thus making chip formation easier (it chips better). The tool needs to take a bite when cutting if the material is ductile it tends want to smear and stick to tools (stainless for example). This is when you start having failure.


            This is a decent description of the cutting process. Does not give full story but comes close.

            [This message has been edited by C. Tate (edited 03-21-2005).]


            • #7
              <font face="Verdana, Arial" size="2">Originally posted by gkman11:
              Got my HF mill (1 1/2 hp) up and running and promptly smoked an American 4 flute TIN coated hss 3/8" tool.</font>
              I've never heard of that brand... I've never seen a Cigar in a TIN coated HSS case either.. that's one hell of a Celebration! Congratulations!!



              • #8
                3 Phase Lightbulb,
                That link sent shivers up my spine. It brought back so many memories of sitting in class watching hour upon hour of every known cutting tool in every conseiveable cutting oil or coolant. I can honestly say I have watched 200 hours of high magnification cutting tool manufactuer coolant and cutting oil films. It was part of my apprenticeship. I have seen shapers and planers and end mills and H.S. lathe tools and drills and face cutters and sloters and core drills and fly cutters and any other cutter you can imagine in every coolant or oil you can imagine. Hour upon hour of film (not video) projector film. Film till your face is on the desk in a puddle of drool. If I ever see another cutting tool film it will be too soon.