Any tips for drilling cast iron

mikew

mikew

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Need to do a repair on my cast iron solid fuel stove, i will have to drill four holes two in the back of the stove and two matching ones in the flu out let to re bolt it on, any tips would be appreciated.
 
Dont centre point it first, I believe cast iron doesnt take too well to being bashed.
Never drilled cast iron though, just remember that from my mechanical ONC (in 1973), good for lathe beds etc as it's dense and absorbs vibration well.
 
HSS bit and keep spraying with WD40 or similar to cool and lubricate, not to high a speed, frequent rests to allow cooling and let the drill do the work.
How big a hole? Start with a small hole first and work your way up.

Edit. As Mat says, don't center punch it!
 
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Cast Iron is very brittle, but machines nicely. You don't want to drop it!
 
Graham W said:
HSS bit and keep spraying with WD40 or similar to cool and lubricate, not to high a speed, frequent rests to allow cooling and let the drill do the work.
How big a hole? Start with a small hole first and work your way up.

Edit. As Mat says, don't center punch it!
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Cast iron doesn't need coolant.
 
Sharp drill (maybe several, could also start small & work up) cutting fluid/oil and be prepared for it to take time.

If the iron has been heated and cooled repeatedly over many years then it may be brittle. I have an old stove that belonged to my parents from >50 years ago, and the iron is now quite fragile.
 
Thanks folks, its a 15 year old machine mart stove and we looked at a replacement today, then when having my tea i came up with a repair idea so its not the end of the world if it fails, as to hole size i guess about 1/4 inch so was going to try a 1/8th pilot hole first.
 
I worked in a foundry many years ago & also on cooker building/assembling. Never used a coolant when hand drilling (air-drills)
A few very sharp drill bits & go reasonably slowly. TBH I probably wouldn't bother piloting first as 1/4" isn't OTT & you might find a 2nd drill bit `snatches` & can be prone to snapping.
 
paraffin was the lube for turning cast iron when I was an apprentice. horrible stuff to machine!
your nose used to run and you would be sneezing like you had a cold all due to the dust produced.
LOL, they used to say you had a cast iron cold. :rolleyes:
 
From what I have read online (from specialist engineering forums), it may be a good idea to wear gloves and safety glasses, because drilling into cast iron can produce chips of swarf which travel at high speed and can penetrate the skin. They also recommend drilling without any lube. Oh yes, and use HSS drill bits at a low/medium speed.
 
gad-westy said:
Cast iron drills/machines quite freely. Or at least most grades do if they haven't been heat treated.
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Applying high temperatures (annealing) to castings, actually helps with any later machining.
 
andy700 said:
From what I have read online (from specialist engineering forums), it may be a good idea to wear gloves and safety glasses, because drilling into cast iron can produce chips of swarf which travel at high speed and can penetrate the skin. They also recommend drilling without any lube. Oh yes, and use HSS drill bits at a low/medium speed.
Click to expand...

It depends on the content of the cast iron. Sometimes it just produces dust as opposed to chips. But you are right no lubrication is necessary for drilling. Only time we ever used any sort of lubrication on cast iron was cutting compound when tapping threads.
 
The drill you use needs to have the sharp edge ground off so you effectively have a small flat leading the cut, if you use a conventional drill bit there's a good chance the drill will bite in and shatter the iron. You don't use lubricant with cast iron as it's self lubricating. Slow speed too as your almost trying to push the cuttings off rather than shear them off.
 
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