drilling cast iron

[JimDRIl]

I have to drill 5 holes in some 3/16 cast iron bench legs. Small holes 7/32 dia.The first one went well going through easily with a new Milwaukee bit. The second hole was really fighting me, seemed to be going nowhere fast. I didn't use and cutting fluid and tried starting with a slow speed with my hand held Makita. Finally gave up to drill another day. Would it help to drill a smaller starter hole, maybe an 1/8 inch? Any tips?

 

[Steve@Advance]

Cast iron drills easy.

At least good cast iron does. The Chinese bench legs are probably some of the lowest grade recycled iron possible. Chances are there is all kinds of impurities in it, pieces of hardened steel, who knows what.

You might try moving over and starting a new hole. If you cant, get a 3/16 masonry drill. If there is something hard in the metal, it should cut through it.

 

[DaveBN]

Did you dull the drill bit on the first hole?
Or could be a hard spot as stated.
Dave

 

[Janicholson]

I agree. Castings from scrap iron can have very nasty hard spots from a ball bearing (or other alloy tramp metal) in the melt. good sharp High Speed Steel (HSS) drills cut cas like butter, and no lube is the recommended technique. The carbon in the iron is self lubing. Ti coated drills from a brand name can also work. Jim

 

[560Dennis]

Could be hitting chilled iron , possible.

I would try a nachi spindle drill ,suggestion.