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torch cut plate fab style of construction
  • Vote Up0Vote Down
    December 2011
    I just saw this on a machinists' group I follow, and thought it might play into GVCS ecology. He is talking about waterjet, which tends to be more precise than torch, and referring to a specific homebrew grinder project at the time, but the same principles seem to apply apply...

    ---- begin included text ----
    Regarding folks' interest in building more of these fine grinders.  
    Any detailed design represents tradeoffs of time vs. materials,
    precision vs. low cost, etc.  More fundamental is the fabrication
    approach:  machined castings vs. tube and angle fabrications vs. sheet
    and plate fabrications.  

    Few mass-produced products are built in the style of Grant's and
    Andy's approach, because of the high craft required to cut, fit, jig up,
    weld and finish so many tube and other precise joints.  In older days,
    the first step in creating any product of this class was to design it
    around castings, in particular requiring a minimum number of machine
    setups to do the finish machining.   More recently, large fabrications
    start as punched and press-formed sheet - think about any modern
    stationary power tool.  Neither of these approaches are accessible, for
    practical purposes, to folks building one-offs in a home shop
    environment.  So folks cut and weld rectangular tube, etc.

    For the last few years, I've quite enjoyed designing
    and making all-sheet-and-plate fabrications, where significant 3-D
    structures are created from e.g. 1/4" plate, using waterjet-cut
    mortise-tenon joints and finger joints for "snap together" assembly,
    typically requiring no jigging and minimal clamping prior to welding.
     Where a volume product might have bends formed using a hydraulic press
    brake, my versions simply have intersecting plates with precise joints.
     From time to time, I've posted photos here, while trying not to draw
    undue attention as both a group moderator and commercial shop owner in
    it for the $.

    The typical successful project completely eliminates
    milling machine operations, and requires only lathe work, to make for
    example shouldered bearing bores.  All the adjustable slide-and-lock
    connections in the grinders, for example, can work fine as raw waterjet

    Anyway, these grinders could be redesigned to be
    functionally equivalent, but constructed with way less labor, by moving
    to waterjet-cut plate fabrication.   The cost tradeoff is up to the
    builder.  Given a set of CAD files, taking a wild guess, for maybe $350,
    someone could order one copy of the grinder, and I'd cut one grinder
    kit, maybe 125 lbs of parts in perhaps 1/4", 1/2" and 3/4" plate, and
    both parties might feel like they got a good deal.   Me doing the design
    is out of the question, but if someone really wanted to do this, I'd
    happily work with them to make best use of the process.

    ---- end included text ----

    This is Bob's shop:
    And Bob at a show

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  • Vote Up0Vote Down
    December 2011
    I have been saying the same thing about the CNC Plasma machines.  I got a Torchmate machine for my shop.  It is not very big only 2x4 foot working area, but it can cut 1/2 inch steel and is accurate to a couple thousandth of inch.  It is also sturdy enough to mount a Bosch Colt router on it to work with other materials or add on another axis to do machining.

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In this Discussion

  • Metz December 2011