Drilling a cast iron soil stack

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Hi,

My father has a blocked cast iron soil pipe where it exits the house. I was hoping to drill a hole in this and clear the blockage (10-15mm hole required). I have a pipe cleaner for a pressure washer that I can poke in then seal the hole afterwards.

What bits should I use? Speed? Lube?

If it cracks were taking apart a bathroom... If it doesn't work we're taking apart a bathroom... One of those ones

Many thanks

Graeme
 
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There shouldn't be any real issues when drilling cast iron, but the outer 'shell' maybe somewhat tougher than expected due to the chilling of the casting.
Use HSS drill bits, centre punch the position before you start. Lubrication won't do any harm - a spray of Duck Oil or whatever.
Drill using a series of bits - maybe 4mm is a good start, working up to the size required. Drill bits up to 13mm are common enough to get, larger ones more difficult but Toolstation so them with reduced shanks which will fit a typical 13mm drill chuck.
John :)
 
Centre punch it very gently - or not at all, use a burr in a dremmel. You don't need any lub as the graphite in the cast iron works as a lub. Check for over-heat as you drill though, but I don't think it'll take that long to go through. Start off with a pilot hole.

Nozzle
 
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Does the soil pipe not vent through the roof ? If so I'd be more inclined to try and clear the blockage from there with proper drain rods. Or try plunging the toilet with a wick mop when the toilet bowl is full of water. Regards david
 
Many thanks for all the advice. Excellent as always.

I selected the drilling position based on planting the drill on the ground. It meant I just had to control it left to right as it started. From then in it was easy to apply even pressure.

Cobalt bit was very slow.
New hss was easy with low pressure and slow speed. Spray of lube to be sure.
Expanded a 4mm-8mm-10mm but it was too small. Enlarged that with an aldi cheapo hss step drill to about 15mm. Needed a lot of pressure and slow speed.

2hrs thinking about it and 10mins to do it lol. Still it worked and I unblocked the pipe in 5 mins then put a rubber bung in the hole for future access.

Thanks again

Graeme
 

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