Counterbores: what Claude and GPT would buy
Two AI models chose on their own, with no web access. Nobody tested these products: this is what each one says, and how to check it.
They disagree: Claude chooses Chicago-Latrobe and GPT chooses KEO
In Industrial & Scientific, Claude and GPT choose the same brand in 52 of 107 categories.
Claude Opus 5.5 · October 28, 2026
Chicago-Latrobe (brand)
It is an established US cutting-tool maker whose HSS piloted counterbores are sized to standard socket-head cap screw clearances.
Not for: Production shops that need carbide or indexable counterbores for high volume.
GPT 6.1 Sol · November 10, 2026
KEO (brand)
Established cutting-tool maker offering piloted counterbores for flat-bottomed fastener recesses; select dimensions to match your screw and clearance hole.
Not for: Conical countersinks or jobs without a suitable pilot hole.
Claude also lists KEO among the brands that matter.
Check before you buy
Where to find Chicago-Latrobe
- Walmart
- Zoro
- Penn Tool Co.
Shops seen in search results on November 5, 2026. A shop missing here may sell it too. Nothing was checked by a person.
Brands that matter
- Chicago-Latrobe: Mainstream HSS cutting tools.
- KEO Cutters: Countersink and counterbore specialist.
- Union Butterfield: Long-standing industrial drill and counterbore brand.
What to avoid
- Using an end mill for cap screw pockets in hand-held drills: it walks without a pilot.
- Running counterbores at drill speeds; slow down to reduce chatter.
Questions
Counterbore or countersink?
Counterbores make a flat-bottomed pocket for cap screws; countersinks make a cone for flat-head screws.