Knee Mills & Vertical Machining Centers
Used Bridgeport Boss 5: Sell or Buy at Auction
The Bridgeport Series I knee mill is the most widely produced milling machine in American manufacturing history and is still the default toolroom mill in thousands of shops. The brand later passed to Hardinge, which carried it through the EZ-Trak CNC knee mills and the Torq-Cut and GX vertical machining centers. Used demand stays unusually deep for a design this old, because nearly every working machinist has run one and parts, tooling, and retrofit controls remain easy to source.
The Bridgeport Boss 5 is one of the earliest numerically controlled Bridgeport knee mills, running Boss, the Bridgeport Operating Software System built with Digital Equipment Corp in the 1970s. Early Boss 3 controls could only cut straight and diagonal lines; Boss 5 added full circular interpolation, a real leap at the time. Built on a Bridgeport knee-mill frame with chromed ways and ball screws on all three axes, it remains solid iron decades later. Today's buyers are mostly retrofitters wanting that proven base for a modern control, such as Centroid or LinuxCNC, plus a smaller pool of collectors. KD Auctions connects sellers to both through its 500,000+ industry contacts.
Buying a Used Boss 5
Toolrooms, plant maintenance departments, prototype and R&D shops, job shops that want a manual mill alongside CNC capacity, trade schools and community colleges, and short-run fabricators. Manual Series I mills draw the largest and most local bidder pool at any machine shop auction because they move without a rigging crew; EZ-Trak, Torq-Cut, and GX buyers are shops looking for CNC capability in a small footprint.
Browse Upcoming Auctions →Selling Your Boss 5
A Bridgeport is one of the most reliably sold lots at a machine shop auction: there is always a bidder. What separates a strong result from an average one is condition rather than year, specifically table and way wear, leadscrew backlash, spindle noise, and whether the power feed, DRO, vise, and original tooling stay with the machine.
Other Popular Bridgeport Models
Frequently Asked Questions
Is a Bridgeport Boss 5 still usable as CNC today?
Some run their original tape-based Boss control as-is for simple legacy programs, but most buyers plan to retrofit a modern control, such as Centroid or LinuxCNC, onto the existing knee-mill frame, ballscrews, and ways rather than keep the original 1970s electronics running. Either way, the mechanical base holds real value on its own.
What is a used Boss 5 mill worth at auction?
Value depends heavily on the condition of the ballscrews, ways, and knee, whether the original Boss control still functions, and whether a retrofit has already been done. KD Auctions provides a free USPAP-compliant appraisal from an AMEA-certified appraiser so you have a realistic orderly and forced liquidation value before deciding to sell. Call 480.455.3910 to start.
About Bridgeport
The Bridgeport Series I knee mill is the most widely produced milling machine in American manufacturing history and is still the default toolroom mill in thousands of shops.
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