a.html

tr ng-repeat="chunksetsBuf in splitChunksetsArray[for_id]"
  td.group ng-repeat="(index, col) in chunksetsBuf"

app.js.coffee

$scope.chunksets = Chunksets.get {}
  $scope.splitChunksetsArray = {}

  $scope.splitChunksets = ->
    index = 0

    $scope.splitChunksetsArray = {}
    buf = []

    _.each $scope.chunksets, (chunksets, kind) ->
      $scope.splitChunksetsArray[kind] = []

      _.each chunksets, (set) ->
        index += 1

        buf.push set

        if index == 4
          $scope.splitChunksetsArray[kind].push buf
          index = 0
          buf = []

      $scope.splitChunksetsArray[kind].push buf unless _.isEmpty(buf)

  $scope.splitChunksets()