Not directly relevant to MMM's but I should be grateful if any of our "hands-on" members could advise how best to drill into cast iron? I ask because I am attempting to drill a small 2-3mm hole into a cast iron item and all I succeed in doing is making a dimple! Tried speeds from 1250 to 2600 rpm.using decent standard metal bits. Would a cobalt tip drill bit be the answer? Simon C.
If the surface where you are trying to drill was cooled quickly during the casting process you might have what is called white iron. It is very hard. Carbide tools might work.
Simon, I have a copy of an excellent Australian publication "Engineers Black Book". It has a mine of information.
For drilling cast iron it recommends a drill point sharpening angle 118 degrees, and for 2.5 - 3mm diameter a spindle speed between 3200 to 2400 rpm respectively. Use a carbide drill bit and a "copious quantity of coolant - Sulphurised Oil/Mineral Lard Oil - Soluble Oil or low viscosity Mineral Oil may be used".
Great to have this helpful feedback, I have ordered some cobalt tipped drill bits and try lower speed and increase if necessary plus lubricant, but, they are only 1/8" holes. Very old casting but it already has several larger tapped holes. Thanks again, Simon C.
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Posted - 22/11/2020 : 12:20:03
