ot---75 lb insert

tunnel boring machine Bertha recently completed Seattle two mile underground
mission

video of change out of perishable cutting tool


YouTube

Gives you some perspective when it comes to working conditions.

The Cheap Bastard, that I used to work for, would told me it was still good and to touch it up...

My city is currently using a 20 foot diameter German-made boring machine to make a several mile sewer tunnel through bedrock. The aim is to reduce the amount of raw sewage that goes down the Maumee River to Lake Erie and points east. The business end of the machine has a bunch of wheel-like tools that look like they would crush the rock rather than scrape or cut. Lots of good pictures on their website.

Updates - City of Fort Wayne

Larry

Imagine changing the inserts on a facemill from the inside of the cutter body. I had the privilege of crawling around Bertha's guts spread out on the ground during seal damage repairs, while she was mining, and after she broke through into the recovery pit. Bertha started mining using disk cutters (the wheel-like tools) to get through the concrete headwall and grouted ground near the start. Later, the disc cutters were swapped for "precutting bits". Only a fraction of Bertha's cutters were changeable from the "comfort" of the interior of the spokes. Any other cutter changes required emptying the area behind and around the cutterhead, making space in front, and doing a hyperbaric intervention. Bertha's "chip augers" were about 5' diameter and just absolutely massively heavy corkscrews. She started out equipped with 24 750-hp VFD-driven motors to drive the cutterhead through a 30-ft-diameter slewing ring bearing.

Bertha was stunningly massive to see it in person. The modular lift tower and crawler cranes needed to do the repairs were no slouches, either. Working on that project has been one of the highlights of my career.