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HTRAL, ? re: centers

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  • HTRAL, ? re: centers

    Reading my way through "HTRAL", 1930 version...I figure at some point the lathe I am working on will actually be used

    Today I must be particularly dense...when turning between centers, "they" always talk about using a live center and some form of dead center (half if facing operation etc.) and using lots of lube, most often oil and white lead.
    If the dead center needs lots of lube so as not to damage the center drilled portion of the work or the center itself, why would one not just use a second live center, solving that issue? Like I said, "dense"...what am I missing?

    "HTRAL" is, as many have stated, quite the useful read.

  • #2
    You only use lube when using *two* dead centers.

    The dead center on the headstock rotates with the work.

    If you use a live center for the tailstock, no lube needed.

    And the reason someone would use two dead centers is that dead centers are more accurate by virtue of having 0 moving parts to have runout in the first place.
    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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    • #3
      Live/dead centers

      [QUOTE=RussZHC]Reading my way through "HTRAL", 1930 version...I figure at some point the lathe I am working on will actually be used

      You are confusing live center and ball bearing centers,they are not the same.
      When turning between centers the "live"center is the one in the headstock/spindle. You can use a dead (not ballbearing) in the tailstock quill and this is when you use the white lead or other lube.
      To restate the live center is in the headstock and the one in the tailstock is either a "dead" center or you are using a ball bearing center.
      Lumpsmith

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      • #4
        Live centre; Rotates with the workpiece

        Dead centre; workpiece rotates on the centre

        Some texts use the term 'running centre' for a tailstock centre with bearings.

        Cylindrical grinders often rotate the work around two dead centres for greater concentricity.
        Paul Compton
        www.morini-mania.co.uk
        http://www.youtube.com/user/EVguru

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        • #5
          In the 1930's they did not commonly use a ball bearing center in the tailstock. They used the same center they used in the headstock. Since it is fixed the and work is turning it has to be a little loose and lubricated. In other words you can't tighten the tailstock center against the work as tight as you would a ball bearing center and that is to allow the white lead or heavy grease to circulate in the center hole and on the center. If the center is allowed to get tight from metal expansion or tightened to much at the start the work and center will be damaged or destroyed.

          A half center is just that, it's a non ball bearing center commonly called a dead center that has slightly less than half of the 60 deg angle ground off and is used to face the end of the shaft and leave the center hole in the end of the shaft.
          It's only ink and paper

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          • #6
            Just a thought about lube for a dead center white lead is no longer out there any more I think, oil??? I use STP or the like,holds up much better than any other oil I have ever used.

            Cookie

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            • #7
              Thanks

              Thanks for the clarification...I get bogged down in terminology from time to time.

              Further, are carbide tipped centers worth the, in some cases double, extra cost?

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