The YUM series is Robbi Group's vertical honing machine line, spanning five sizes from the YUM 200 to the YUM 400. Vertical movement runs on recirculating ball screws with linear guideways, and the stone pressure adjusts through an automatic hydraulic cycle.

Why vertical honing for long, large-diameter tubes?

A horizontal hone lets the stone weight sag against the bore, which shows up as ovality on a long tube. The YUM's vertical spindle lets gravity work with the cut, so a 2,300 mm tube comes out rounder with less coolant — the reason oil, gas and hydraulic tube shops hone vertically.

• Ø22-400 mm bores, up to 2,300 mm length
• Automatic stone-pressure cycle for taper and ovality
• Power-absorption detection finds small-diameter points
• Belt-breakage automatic stop

Against a horizontal hone, the YUM lets gravity hold the geometry — the reason a long tube comes out round without a second measuring pass.