Drilling Through Manhole Cover Update Fao Builder Please

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woofgang | 12:38 Tue 04th Mar 2014 | DIY
9 Answers
Thanks for your advice. Bricks are now lifted and relaid loose with drainage gaps. I tried drilling holes in the base of the cover (its solid, not blooming would be!) but the bit wouldn't bite. Its a decent quality bit, Black and Decker, for drilling metal and the drill is a mains powered De Walt with plenty of oomph.

Do I need to buy a better bit and if so what please? or am I doing something wrong?
Many thanks


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Cast iron can be tough. Yes I think new bits might well help. So might trying a pilot hole first ? I'm unsure what qualifies as better though. I tend to go with the thought that you get what you pay for, and invest in the dearest in this sort of situation, even if there is a chance I'm being ripped off. Would a centre punch make an impression in the cast iron ? If the issue is the bit slipping it may be worth a try.
Not that I have bought them but I know the TV sales channels (well at least one of the major ones) sometimes boast of some kind of drill through anything super bit. Could be just marketing guff though.
Be careful with a centre punch on cast iron. It can tend to be a bit brittle.
Question Author
Its not cast iron, at least I don't think so. The shape appears to have been made by bending the metal, not casting it.
Ah, you have no excuse then ;-)
I'm thinking a centre punch and smallish drill bit to start the holes might be the answer. The metal is probably galvanised and this can act something like a lubricant so the bigger bit skids about instead of biting in. A few blows on the punch to make a decent dent might help. But as the Judge says, beware the punch doesn't shatter
Sounds like galvanised steel, Woofters.

I agree with a pilot hole first. It really does make it easier. A brand new 4mm drillbit for steel, followed by a 6 or 7mm bit. Then maybe a 10mm to finish.

Grip the drill very tightly in case the bit catches in the steel and tries to wrench your arm off.

What diameter bit are you trying with?
Oh and maybe stand on the workpiece or if it grips & turns you may get a nasty bruise on something !
Question Author
thank you Builder. I just went in with the biggest diameter drill first. Will try starting with a small one...and yes not new. Thank you all for your input :-) Will report back.

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