It’s 1/2”.
I have a full set of taps up to 1/2” and I have a bunch of larger ones from my father who was an industrial electrician.
None are pipe taps! 18 thread
Just buy a 1/2" NPT tap--assuming there are still enough threads left to chase. Otherwise, Helicoil or equivalent. I'm sure you can find a bushing that would work, too. Replacing the volute of the pump would likely be around $300-400.It’s 1/2”.
I have a full set of taps up to 1/2” and I have a bunch of larger ones from my father who was an industrial electrician.
None are pipe taps! 18 thread.
Ya it’s a $1500 pump.
I talked to a pump place and they talked about replacing the cast end.
Kicker is the house is for sale so I need to do something.
Once again, if it's 1/4" NPT, drill and tap to 3/8" NPT. $20-30 of cheap tools for a one-time job, and cast iron drills and taps like butter.Are you sure that's 1/2"npt? 1/2"npt is 14tpi.
1/4"npt is 18tpi, which is approx 1/2" diameter.
Chase with tap, get a new plug, copious wraps of teflon tape and teflon paste
Indeed. Buy a 3/8" NPT tap and 37/64" bit. You should be able to walk out for about $20 or less. You don't need the really good stuff as you're drilling and tapping cast iron--and probably only using it once. An adjustable wrench is fine for driving the tap and you don't need to take the pump apart--unless you feel like a rebuild of the pump seal and gaskets.It's 1/4 NPT, not 1/2".
It is tapered, as it's a pipe thread--National Pipe Thread, even.Drain plug appears to be tapered
Yep. That's why you need to do the tapping iteratively.Thanks guys.
Is the plug tapered as well?
Harbor Freight (or Princess Auto or whatever it's called up there) carries a set of pipe thread taps for not much money. Be careful on depth when tapping tapered threads. Start at 1/3 depth or so, then back it out and try the fitting....then give it another turn at a time until you've got it where it you want it.
I was thinking drilling the hole bigger then braze a bushing in. Bushings are cheapFor that matter, I'd be willing to use JB Weld to fill the hole, then tap with a 1/2" NPT tap. With the fairly low pressure of that pump--likely no more than 60 PSI--it's ll do just fine.
If you get the tap set, it will have both 1/4" NPT as well as a 3/8" NPT. I'd start with the 1/4" and try to clean up whats there, and try a new 1/4" NPT fitting to see if it catches enough thread to tighten appropriately. Use some pipe dope to prevent galling. If not, then step up to the next size, 3/8" NPT.Should I drill out the stripped hole first or just go for it?
I have a set of numbered drills.
I dont think it has enough taper to make up for stripped threads. Far from an expert on this, thoughWon't the tap just have to go a bit deeper seeing it is tapered?
There was still lots of drain plug left before.
Deeper yes, but the wall thickness isn't sufficient to go deep enough to get enough thread I think. You might be able to enough thread engagement to hold it and rely on rtv to seal it upWon't the tap just have to go a bit deeper seeing it is tapered?
There was still lots of drain plug left before.
for most folks that would probably be a job for JBWeld and duct tape... whatever holds just long enough to sell.Kicker is the house is for sale so I need to do something.
They good quality or off shore?I have a couple of npt pipe tap sets (1/4 to 3/4 or 1”) for sale for $25-30 if you’re interested. Pm me and I’ll send you some pics
Good idea. I changed my order. But will these get clogged if there are any debris? It is pumping from the lake. I guess I could poke a stick in to free anything.