thread chasers

nelsonnucla · July 31

I have a cast iron irrigation pump that has a 1 1/2" outlet port with dinged/rusted threads. Looking on ebay your dealing with inside threads and outside threads. Their were many devices for chasing and outside thread, but not for an inside thread, except for 1/4, 1/2, etc openings where NPT taps would nicely chase a thread. Many chasers for spark plug holes offered. Would I have to take my well working pump to a pump repair place where they would have a chaser for my 1 1/2 outlet port .—John

hot_rod · July 31

just use a 1-1/2 pipe tap

Cast iron threads do deteriorate if there was any leak, they rip and tear easily

Clean them up and use leak loc or Loctite to insert the new fitting

Larry Weingarten · July 31

Hi, Is this what you're looking for? https://www.ebay.com/itm/284186188887?epid=13005040614&itmmeta=01J43ES1XQRWY1JGT39MA8FTE1&hash=item422ad11c57:g:SJkAAOSwvv1amdu~&itmprp=enc%3AAQAJAAAA4JtEq2pYSMkiI0LdUlfB8%2Bly717IchydT2nDjgvbCIbHv920%2FosXepvup1FkV2%2BfFutdTEPKqt2fCNM6rLnXTLPrBD0gMBOwjS85fNldq6h91h4wPXgDzoSyn7%2FjwS9f18Ajh%2F1zpGFxsDqv1aukQ2emJl%2BeqxSu8gbFRNmV1Cob7exre0KjRSqMkSkdoE89oRpRuzbN%2FvYtjEsW1K1Ksv7tKOKfjWGO8GY4cT0X45DztHxz2%2FqKoBefEjmy%2B2OmM6Hj3V0KPBga9T%2Fw0WPD9Ssgduo0Llb9v2zhFkJrQkUg%7Ctkp%3ABk9SR_6e5O6gZA

Yours, Larry

leonz · July 31

Is your irrigation pump a centrifugal self priming pump? Are you using fire hose hand line connections?

As Larry mentioned you can purchase a National Pipe Thread starting tap to do this. You should have a National Pipe Thread bottoming tap as well.

EBEBRATT-Ed · July 31

If you're looking for cheap pipe taps just for cleaning threads McMaster Carr sells "imported " tap which are good quality and pretty reasonable although you probably don't want to buy them for one job.

Hears what you can do to "make" a thread chaser.

Buy a 1 1/2 X6 nipple and put it in a bench vise vertically. Take a hacksaw or sawzall and cut down through the threads (cut right across so your cutting through the middle of the nipple cutting the threads on 2 sides of the nipple).Cut to the bottom of the threads. Turn the nipple 90 degrees and make the same cut again.

Take a torch and heat the threads and tap the threads with a hammer on the right-hand side of each cut. Just tap them in about 1/8" The left side of the cut is the cutting side leave that as is. Do this for all four cuts.

Now you have a home made pipe thread chaser.

mattmia2 · July 31

You can also get a file with the same pitch as the threads that you can try your luck with.

JUGHNE · July 31

Ed, you stole my thunder……I have done that and it does work.

pedmec · July 31

you can go to harbor freight and buy a SAE NPT pipe tap kit for $60 dollars. don't know how good the metal is but if you're only chasing the threads then they work fine. i have never had a problem chasing threads with them. especially in my area nobody seems to be carrying them much anymore.

nelsonnucla · August 1

thanks all for the thread chasing comments. In talking to a farmer friend, lo and behold he had a 1 1/2" — 11 1/2 npt tap that I quickly put to use. I was able to clean the threads and penetrate to a depth of about 3/4" which I thought was short. Trying to go further required a lot of pressure on my 10" crescent wrench to I stopped. Inserting my close nipple it would only screw in about 3/8". Any further effort I thought might colapse the nipple using my 18" pipe wrench. I took what I got, put on 3 wraps of teflon tape and installed the nipple. It seems to me the taper of the existing hole is not the same as the tap/nipple, so that the tap and the nipple bind up to soon,—John

ChrisJ · August 1

https://forum.heatinghelp.com/discussion/comment/1807235#Comment_1807235

I'd want about 4 turns on that size pipe.

A 10" wrench isn't really good for tapping a 1.5" NPT thread. In my opinion you want something T shaped and that will give good leverage.

hot_rod · August 2

Good idea to use cutting oil also. The tap will b ind without proper lube. An 18" wrench should be plenty if the existing threads were cut deep enough.

There is a difference between cutting or clean ing threads.

DCContrarian · August 2

"I'd want about 4 turns on that size pipe."

1-1/2" is 11.5 threads per inch. So 3/8" is 4.3 turns.

thread chasers

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