Tunnel Boring & Heavy Civil Equipment worked example

Cutterhead Fabrication Cost at 98% first-pass weld yield: a worked example

Push first-pass weld yield up to 98% and the picture changes. This example computes every intermediate figure at that operating point. Use it when bidding a custom cutterhead build to size weld-shop labor and steel exposure against the hub and bearing setup that is fixed regardless of cutter count.

The inputs for this scenario

  • Welded cutter housings in the build: 48 housings (unchanged)
  • Fabrication cost per welded housing: 3,200 $ / housing (unchanged)
  • First-pass weld yield: 98 % (raised for this scenario; the documented default is 85)
  • Hub and bearing-plate machining setup: 95,000 $ (unchanged)

Working through the calculation

  • Applying the documented formula (Total = housings x fabrication rate x (first-pass yield รท 100) + hub setup) to the inputs above produces each figure below.
  • At this operating point the engine returns 245,528 $ for total cutterhead fabrication cost, the number this scenario is built around.
  • At this operating point the engine returns 5,115 $ / piece for cutterhead fabrication cost per unit.
  • At this operating point the engine returns 150,528 $ for variable cutterhead fabrication cost.
  • At this operating point the engine returns 95,000 $ for fixed cutterhead fabrication cost adder.

How this compares with the baseline

  • Against the tool's baseline example, where first-pass weld yield sits at 85% and the headline result is 225,560 $, this scenario comes in 8.85% above the baseline at 245,528 $.
  • It multiplies welded cutter housings by the per-housing fabrication rate and first-pass weld yield, then adds the fixed hub and bearing-plate setup. The value of this scenario is the size of the gap it exposes: that gap, priced out over a year, is the budget you can justify spending to close it.

Results at a glance

  • Total cutterhead fabrication cost: 245,528 $ (headline result)
  • Cutterhead fabrication cost per unit: 5,115 $ / piece
  • Variable cutterhead fabrication cost: 150,528 $
  • Fixed cutterhead fabrication cost adder: 95,000 $

Run it with your numbers

  • Every input above is editable in the live Cutterhead Fabrication Cost calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.