My new Delta Foundations spray support cylinder does not fit through the sprayer hole in my cast iron sink. The previous model Delta sprayer did. The hole is just a hair too small. Any suggestion about how I can enlarge the diameter of the hole slightly (less than 1/8" without removing the sink? I cannot (easily) attach wood to provide a pilot for a carbide hole saw. Wondering if anyone has had any luck with a hand-held file or a rotary file used in a drill.

Thanks in advance for any help.

you may chip the enalem coating slightly but the flange of the bottle holder will more than cover it.
i would use a rotary file as you will have more control.

If you have the correct hole saw mandrel, you can "modify" it so that you can attach the carbide saw first, then attach a hole saw that fits into the opening to act as a guide while you enlarge the opening.

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or the equivalent

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

He wants to make the holes larger, NOT "polish" them.

A carbide burr will enlarge the hole.
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They are not expensive. They work best in a high speed die grinder but,in a pinch, they can be used in a drill. It takes longer in a drill. Hammer drills have higher speed (2400 rpm), so use one if you have it.