I want to drill holes through a cast iron railing in order to repair it. I have followed what I understand to be the correct procedures, ie lubricating and slow drilling but with little luck.
I have come to the conclusion that I am using the wrong bit so what I want to know is, what is the correct bit?

JOHN COUGHLAN, July 2007

in relation to the hair line crack on the log burner have you got access to a arc welder if you have i would use cast rods and weld it first grind down the crack very gently to make a good root then weld it takin your time so as not to heat the cast to much at once then grind the weld off for a neat finish

hobb, June 2010

no lubrication is required but a good med to fast constant pace with as much pressure as possible on is key use a small drill like 6mm hss bit as a pilot first

hobb, June 2010

i have a log burner made off cast iron and there is a hair line crack on the top is there anyway off fixing it

kev jones, February 2009

you don't say what size hole you're trying to drill.Start with a small bit..say 5mm,then gradually increase bits in2-3 mm increments...don't try to drill a 10 or 12 mm hole in one go.Also, for best effect,try and have the workpiece positioned where you can get your full body weight behind the drill..ideally workpiece on the ground,you standing above it with drill at 90 degrees vertical.If that fails,try cobalt bits...expensive and brittle,but very sharp

Chris, September 2007

You don't use lubricant to drill cast iron, it's always machined dry.

Any good high-speed steel drill bit should work.

Wear eye protection, the swarf is fine. I speak from experience, it hurts.

Ken, July 2007

Cast Iron is self lubricating therefore no other lubrication is needed.
Slow speed with a sharp High Speed Drill is all that is required.

David Johnson, July 2007