Boring mill repair, on your floor
Cavco repairs horizontal boring mills where they stand. Column and saddle ways reground and scraped in place, the table relevelled and its index put right, the quill and spindle brought back true, hydraulics, lube and controls, and the whole machine realigned with lasers and levels before we leave. A boring mill is the machine that does not move, so the shop comes to it, and has since 1980.
What goes wrong on a boring mill
A boring mill is a column that has to stay square to a table that has to stay level, with a spindle that has to run parallel to both, and a bar hanging off the end of it. When a bore comes out oval or a face comes out of square, one of those has moved. The first job is finding which, with a measurement, not a teardown.
- Scored, worn or loaded ways under the column and the saddle. The head no longer travels square and the table no longer travels parallel. Reground and scraped in place, then the geometry proved.
- A rotary table that will not index true, will not clamp, or sits out of level to the ways. Bearing, clamps and index put right where the table sits.
- Quill sag at extension, a quill that rocks in its bore, spindle bearings running hot or out. Brought back to a running fit and trammed to the table.
- Pressure lost on a hydrostatic column, clamps that will not hold, cylinders and valves. The systems that let a machine this size move at all.
- Starved ways, way covers, coolant and oil where they should not be. The small faults that take the geometry with them if they are left.
- Servo and spindle drives, motors, encoders, and the control faults that come with the mechanical job. Retrofits case by case.
- Bent quill, shifted column, a table off its bearing. Measured against itself with lasers and levels, then realigned, and you get the numbers.
- The mechanical drives on the older machines, worn gears and shafts, put right so the feeds are smooth and the backlash is out.
Too big to move is the point
Sending a boring mill out for its ways means rigging it out, a foundation cut, a truck, months in someone else’s shop, and the same again coming home, and most of that time nothing is being ground. We developed a proprietary process to grind and scrape ways in place, on the column and the saddle, hardened or soft, and to realign the axes while we are there. Against sending the machine out, that is four to six weeks of downtime you do not lose, on a machine that was never going to move anyway.
The way grinding is described on its own page. The measurements that decide what a boring mill needs, and what it holds when we leave, are on the alignment page. A machine that needs everything is a geometric rebuild, done in place on a boring mill, one axis at a time against the rest.
Boring mill repair by make
Every boring mill is the same three questions. Is the column square, is the table level and true, does the quill run straight. Where each make loses one of them is different.
- Boring mill repair on Wotan machines, the Rapid 5P and the smaller Wotans, is the column and saddle ways, the hydrostatic system that floats the column, the gear trains, and the rotary table, and it is the machine this shop has worked on more than any other of its kind.
- Boring mill repair on Giddings and Lewis machines, the BTMC among them, is most often the column ways and the saddle, ground and scraped in place, with the head trammed and the table relevelled afterwards.
- Boring mill repair on DeVlieg Jigmils and the 65 series is a precision job by the machine's own standard. The Jigmil was built to jig-bore tolerances, and the repair holds it to them, quill, spindle and column square.
- Boring mill repair on Toshiba TD 60 and TD 80 machines is the table and saddle ways, the rotary table, the quill, and the drives and controls on the CNC versions, done in place at the plant.
- Boring mill repair on Lucas, Union and Kuraki machines follows the same measurements, column square to the table, spindle parallel to the travel, quill true at extension, and the repair is whatever those numbers say it is.
- Boring mill repair on Scharmann, Skoda and other floor-type machines is the biggest iron there is. Nothing about it moves, so everything about it is done on site, the ways, the table, the alignment, and the proof.
Where we go
Boring mills live in shipyards, power plants, forges, heavy fabricators and the big aerospace shops, and they do not come to us, so we go to them. Connecticut, Massachusetts, Rhode Island and the Hudson Valley are a day’s drive. Vermont, New Hampshire and Maine we schedule as a trip. Beyond New England we have gone wherever the machine is for more than forty years, and we tell you what the trip adds before you decide.
A boring mill spindle on its own is covered on the spindle page. A fault that arrived with an alarm on the screen belongs with CNC machine repair. Telling a column problem from a spindle problem from a table problem is diagnostics.
Questions we get
- Yes, and that is the whole point of how we work on them. A boring mill is rigged once, when it is installed. Everything after that happens on your floor. We grind and scrape the column and saddle ways in place with a proprietary process, rebuild the table and the quill where they sit, and realign the machine with lasers and electronic levels. The machine never leaves, and the downtime is days to weeks rather than months.
- Sometimes. As often it is the column, which has to be square to the table in two planes for a bore to come out round and square, or the saddle ways, which decide whether the table travels parallel to the spindle. We measure the machine against itself before anything comes apart, so the answer is a number rather than a part ordered on a guess.
- A boring bar extended on a quill droops under its own weight and the cut, and a worn quill bore lets it droop more and rock while it turns. The fix is the quill and its bore brought back to a running fit, the spindle bearings set right, and the head trammed to the table, so the bar runs true at full extension and not only at the nose.
- The table bearing and its clamps, the index mechanism, and the level of the table to the ways all get measured and put right in place. A table that indexes true but sits out of level still bores crooked, so both are checked, and you get the figures for both.
- Yes. Hydrostatic and hydraulic systems, lube systems and leaks, gear trains, and the electrical side, drives, motors and control faults, where they come with the mechanical job. A control retrofit on iron that is worth it is case by case, and we say plainly when it is not.
- Yes, and it is the cheapest part of buying one. A geometry survey before the money changes hands tells you what the machine will hold and what it will cost to make it hold more, which is a different number from the asking price.
- Wotan, the Rapid 5P and the smaller Wotans, more than any other. Giddings and Lewis, including the BTMC. DeVlieg, the Jigmil and the 65 series. Toshiba TD 60 and 80. Lucas, Union, Kuraki, Scharmann, Skoda and Nomura. Table type and floor type. If yours is not on the list, ask.
Reviewed September 2026 by Cavco Machine Tool Rebuilding, LLC.
Tell us which mill and what the bore is doing
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