old rusted cast iron rodding access point advice!!!

[andy1020]

hi folks,
i have a 1930s houe with cast iron drains

main drain seems to be ok, it's the smaller rainwater drain to the rear of the house that is blocked. The kitchen sink drains into it (I know you don't mix rain & foul nowadays but that the way it was done then..)

problem is the rodding point made from cast iron is totally rusted. It looks like its never been removed and the bolts / screws are just a rusty bump.

I tried with a hammer and chisel to clean them up to turn but not happening.

What's the best way to remove the cover?
drill out the screws? grind off the heads? or what?

Can I smash it off and buy a new cover that will fit or if i break it will i need to replace the whole section (which is half buried in concrete so not a good option if i can rod it and clean it ok)

thanks!!

 

[Burnerman]

Grind off the screw heads, then gently tap the cover until it comes free....(cast iron has no flexibility so be careful)!
Once the cover is off, cut the remainder of the screw away, centre punch the middle of the screw - or as least as close as you can judge it - and then drill down a series of holes up to 7mm diameter.
This will be an approximate tapping size for an 8mm tap which will cut new threads, allowing a new bolt to be fixed.
Cast iron is fairly soft (or at least the inside of it is, where it hasn't been chilled).
Thats what I'd attempt, anyway!
John

 

[andy1020]

ok great cheers will grind them
once the head is ground off and the cover removed, is it worth trying heat and mole grips to turn what's left of the screws?
how does cast iron react to a blowlamp?!

(used to do this on car parts not sure about drain pipes!!??)

 

[Burnerman]

Some heat is certainly worth a try, but you'd be looking at the heat from Mapp gas really - it certainly wont hurt the cast iron.
If you can get a huge grip on any projecting stud using a Mole wrench, it may start to come out but the threading idea is viable (says he, possessing many taps and dies ).
I just think its really worth thinking this one through - you don't really want to disturb ancient drains unless its unavoidable!
John

 

[andy1020]

sorted, many thanks. yes it ground off no problem and they turned with grips easily new bolts in, drain unblocked, happy wife
thanks