"N8N" wrote in message
...
On Oct 24, 2:31 pm, Matt wrote:
My house has a drain pipe for the kitchen sink, and the pipe gets
plugged sometimes. Then you have to remove the plug or bung from the
cleaning hole and run a snake down the pipe.

Last time I had to unplug the drain, I wanted to replace the (60mm
plastic) plug. The drain hole is in a fitting that looks like cast
iron, and the house is about forty years old.

I had a lot of trouble getting the new plug to engage the threads of the
cleaning hole because the threads were rusty. I took a stainless-steel
wire brush (and I think some Liquid Wrench) to the threads, but that
didn't seem to do much.

So I just put the old plug back in---that wasn't too hard to do. But I
am afraid of cross-threading the plug and ruining it sometime.

Next time I have the plumber over to do some work I thought I might ask
him to do something about those threads.

Would he have some kind of tool to clean out the threads without much
risk of messing things up?

Probably the easiest thing to do would be to get *two* new metal plugs
for the hole - preferably iron. Take one, and with your 4" angle
grinder, cut slots across the threads so it looks similar to a very
large tap. Thread that into the hole and tighten it well, letting it
clean the threads of the old pipe. Then remove it and install the
second, unmodified one as normal with pipe dope.

************************************************** **************

I recently did exactly that on the thread for a sink drain. It cleaned them up a
bit, but notthe heavier rust further in. Maybe I should try it again, but try
hardening the modified thread before use.