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Alternative use for VCGT tip

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  • Alternative use for VCGT tip

    I'm always checking out eBay for bargains or novelty tooling, and bought an as new 20mm square lathe tool holder with 6 unused VCGT 160401 tips. A misstyped number, the more knowledgable might think, but no, the last figure is indeed a 1. The tip rad is 0.1mm so the tip diameter is only 8 thou.
    Seemed like a good idea at the time, but you need a very fine feed rate and I have yet to find a useful application for it. Maybe sharp internal corners.
    The tips are ARNO grade AL10 for aluminium, very sharp.

    I have had great success using them for engraving scale divisions for the lathe cross slide. I made a replica of the scale in aluminium, and set it in a three jaw chuck mounted on the rotary table. I got it running 0.0005" tir with the axis vertical on the mill. I turned a holder, one end faced off and a little smaller diameter than the tip length, threaded to hold the tip, the other end to fit a 16mm R8 collet.
    The idea is to plunge with the quill to the three different depths for the tens, fives and remaining numbers. I chose 3, 5 and 6mm line lengths as being nearest to the originals, easier than working in thou.
    Having locket the top pulleys, I then had to deal with the quill drive spline backlash, about 3 degrees. I drilled a hole in the side of the tool holder just above the tip, inserted a 10" long 3/16" bar and found a long spring to keep the splines free of backlash.
    Cuts about 6 thou deep worked fine pushing out a curved burr which was easy to break off. The engravings are about 10 thou wide, and after gentle fettling, look really good, better than I expected.
    Of course, I forgot one thing when taking the tool out. I loosened the drawbar and tapped it to loosen the collet and the tool turned sharply and cut my finger, I had forgotten the tension in the spring. I couldn't see the spring from where I was standing.
    With success with the aluminium one, I turned off the old engravings from the original steel one and it came out really well.
    I looked at the tip through a microscope and there was no wear or damage at all.

    Now I am looking out for 3/32" number stamps, no hurry

  • #2
    Actually, that's a 0.004" tip, not 0.008".

    Nice use of the tool.


    • #3
      No, it is the ISO designation, also, I was not sure myself so I put the optical centre finder in the mill (20X) and actually measured the diameter. definitely 8 thou diameter, or 0.1mm radius.


      • #4
        Mr Mart, you nearly confused me.

        I agree that 0.008" DIAMETER is close enough to 0.1mm RADIUS ... but can I suggest it would have been an easier read for you to have talked radius and diameter with some consistency.



        • #5
          Did you read the first two lines of #1? I know that there are large numbers of people living in North America who have no idea what a millimetre is, probably the same ones who call a minority sport "The World Series".


          • #6
            old mart, regardless of the unit of measure or whether ISO or ANSI designation used to define the insert, it's always given as radius with ONE exception: round inserts. Those don't have any numbers beyond the "I.C." (inscribed circle) size that makes up the first two numerical characters of an ISO designation or first single number (in eighths of an inch) if an ANSI designation. I also find it confusing if someone says diameter when discussing corner radius; a diameter is 360؛ of surface to me.

            You should know that not everyone over on this side of the pond is ignorant of millimeters. When it comes to insert designations I'm fluent I'm both common "languages", ISO (metric) and ANSI (inch) systems. The one I hate here is Iscar, who made up their own. A CCMT32.51 is a CCMT09T304, but in Iscar over here it's 3-1. Grrr...

            When you get into the smaller screw-down (a.k.a. "positive rake") inserts, I actually like the ISO system better. The reason is that giving the last position of shape nomenclature as two digits works better. A VCGT331 in ANSI is a 0.0156" (1/64th inch) corner radius while the same insert given in ISO is a VCGT160404. That would convert to 0.3968mm, close enough to the 0,4 of the designation. When you get smaller than a "1" in ANSI, the manufacturers differ in what they use for ANSI. Some make it a "0", others use "0.5" and the "0" could be a 0.008" radius or a 0.004" radius. Given in ISO format, it's always easy and CLEAR.

            Just refer to corner radius, not diameter. We're not completely inept but are easily confused.


            • #7
              That's what I said "the tip rad is 0.1mm so the tip diameter is only 8 thou". I felt the need to dumb it down for those who don't have knowledge of the metric system, and there is plenty of evidence of that on this forum.


              • #8
                Would it have been easier to state:

                "The tip radius is 0.1mm (0.004")" and not throw the word diameter in there?

                That is all, carry on.


                • #9
                  Originally posted by old mart View Post
                  That's what I said "the tip rad is 0.1mm so the tip diameter is only 8 thou". I felt the need to dumb it down for those who don't have knowledge of the metric system, and there is plenty of evidence of that on this forum.
                  There was no indication of a problem with the metric system; Metric is easy to understand. The problem was the gratuitous interjection of "diameter" to describe an arc of much less than 180 degrees. I guess it's possible to use the term diameter to describe an arc, but all the formulas that I remember (and see in a quick search of the web) use radius.

                  At the end of the project, there is a profound difference between spare parts and left over parts.

                  Location: SF East Bay.


                  • #10
                    I agree with Dan on this. I would never use "diameter" to describe a radius. It has nothing to do with metric vs. inch systems


                    • #11