Avoid Producing Scrap by Checking Metal Line

Metal line can be checked in a number of ways.  In this article, we outline the use of stringing piano wire through the mill with the tooling installed.

Please refer to Profit Pointer number three (3), Tube Mill Alignment.  Check point number 10 discusses the use of piano wire to check the metal line of the side roll boxes.

Install both the driven and idle passes of tooling.  Using a simple boat winch (see below) with .045” piano wire installed, string the wire through the mill from the first breakdown to the last sizing.  The wire is normally tied off in the jaws of the cutoff (on center) and then tightened with the winch through the entry mill.

Boat Winch
Make sure the piano wire is in the center of the bottom driven rolls of all passes (Figure 1). Use a scale that can measure across the total width of the bottom rolls.  For example, if you have a 6.000" wide roll, the piano wire should line up on the 3.000" mark of the scale.  Do this for each of the bottom driven rolls.  Check to make sure the wire will not be hindered by anything mechanical.  The wire should free float in the bottom of all the driven rolls.

Figure 1
The wire is imitating the bottom of the strip/tube throughout the entire mill.
The wire should touch the bottom throat of each driven pass, thus ensuring proper alignment of the bottom driven passes.
Next, check the centering by comparing the side roll passes to the wire.  Adjust the side roll passes together until there is ± .125” bottom rim clearance.  Now check for centering of the rolls compared to the piano wire (Figure 2).  Adjust as necessary.

Figure 2
We now can check for proper metal line of the side roll passes.  It is very important that the side rolls are at the correct height to the formation of the driven passes.

In check point number 10, lower right-hand corner, you will see the illustration of checking the metal line of the side rolls. 

The metal line is measured from the bottom of the side roll to the bottom of the piano wire.

The metal line measurement for each side roll pass should be on your tooling prints or setup chart.

Place a straight edge on the underside of the rolls (Figure 3).  Ensure the straight edge is placed on the flat of the underside of the side roll tooling.  Next, using a gauge block of the same dimension as the metal line, place this on top of the straight edge in the area between the side rolls, where the piano wire is strung.  Then adjust the side roll box up or down to meet the piano wire.  Note:  If you are too high, move the side roll box down past where you need to be, and then come back up so the backlash of the lead or jack screw is eliminated.

Figure 3
Many users find it easier to make a fixture that has the gauge block mounted on it.
This procedure will ensure the side rolls are at their proper heights.

Written by Robert Sladky, VP of Tube Mill Engineering

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