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View Full Version : Rebuilding Female threads on a LMI pump


AcroSteve
12/07/2006, 06:41 PM
I picked this up cheap, but I wonder if I can rebuild these threads on the outlet of the pump.

http://i11.photobucket.com/albums/a159/sbowman01d/DSCN3517.jpg

I am pretty sure it is PVC and my fitting will tighten up in what is left of the threads. I have not tried the pump out yet, as i have it totally dissasembled for cleaning, so it might not even leak. But I wonder if plastic epoxy would stick to the PVC. And if a coating of silicone greas on the threads would allow it to release from them

Thoughts?

BeanAnimal
12/07/2006, 08:17 PM
Plastic epoxy will stick to PVC. I would coat the PVC and thread it in... then buildup the area to what it used to be... you may have to do it in layers as the plastic epoxy will outgas quit a bit and may pull away in some areas or fissure inside and allow a leak path.

Bean

Kmiec123
12/07/2006, 08:20 PM
Could Plastic weld to build up and retap threads, possiblly..gotta cheep site for the taps....Just a thought...Carl

AcroSteve
12/08/2006, 04:32 AM
I thought I might set some stainless screws in the main peice to positively anchor the epoxy to. So you think I would be better off not doing it all at once? I had some concern about the multiple planes of adhesion beinig botential sources of leaks or fractures.

I should get the screws set this morning. And I already have the epoxy, so we will see how it goes.

MinibowMatt
12/08/2006, 08:14 AM
I would look for a good quality plastic resin, fill in that hole, and then re-drill and tap it out again. The Plastic *should* bond to the new resin, but I dont know what kind of plastic you have there, or which resin you can get your hands on.

If you cant fill it, Go with Bean. Thats the next best thing IMO

BeanAnimal
12/08/2006, 08:33 AM
I was going to suggest the anchors.. but if you use plastic epoxy it should chemical weld (if it is a PVC base). In some cases anchors such as that can cause fracture paths... but you should be ok either way here. Make sure it is the plastic epoxy with solvent in it.

Bean

das75
12/08/2006, 09:16 AM
could you grind out enough area for a slip to FPT coupling then embed the coupling in epoxy or resin.

BeanAnimal
12/08/2006, 12:49 PM
DIY SLIP is awful hard to achieve. A SLIP socket is tapered to allow a tight fit and uniform solvent contact. I have never had much luck trying to do my own. Seeing that there are some threads left, trying to use them is likely a wise idea.

das75
12/08/2006, 01:20 PM
What I'm trying to get at is use a portion of a manufactured coupling.

eg. cut a coupling in 1/2, grind out enough of the pump so the coupling can get a good seat (where epoxy can't seep past), glue in place.

BeanAnimal
12/08/2006, 01:24 PM
He has that.. There are threads already there that he stated did a decent job of accepting a PVC threaded adaptor. He is going to thread a the adaptor on snug, then surround the adaptor with epoxy. He is also going to use a few studs screwed into the existing flange. These will give the epoxy something to grab onto in addition to the PVC pump flange :)

IMHO grinding the threads out of there and trying to fashion a SLIP type joint would be a step backwards. Then again that is just my opinion.

Bean

AcroSteve
12/08/2006, 03:56 PM
The threads are not pipe. They are stright threads of some sort and there is a special profile at the bottom underneath the teflon insert in the pic. So, re-drilling is out of the question.

I should make some progress tonight.

AcroSteve
12/09/2006, 12:11 PM
Well, it ain't pretty, but I accomplished what I needed to. Which was to rebuild the threads to the point of providing additional support to the piece that threads into them.

Here is what I started with. I might have had better results if I had not been overly concerned with gluing the two pices together. I am not sure I needed anything at all on the white pice to keep the epoxy from sticking to it.
http://i11.photobucket.com/albums/a159/sbowman01d/DSCN3519.jpg

http://i11.photobucket.com/albums/a159/sbowman01d/DSCN3524.jpg

You can see some voids in the repair. The mixture was thicker than I had imagined and I did not work it into the nooks and crannies well enough.
http://i11.photobucket.com/albums/a159/sbowman01d/DSCN3525.jpg

This stuff smells just like weldon 40.

But overall, I think This $5 LMI pump will work just fine.

BeanAnimal
12/09/2006, 12:29 PM
be careful with the teflon tape... you can put a lot of force on those thread with it... better to use the paste.

AcroSteve
12/09/2006, 01:11 PM
Yea, I hear ya. I had it on there to keep the "epoxy" from sticking to the valve. It is already removed.

fishytoo123
12/09/2006, 04:17 PM
You should have tried JB Weld and rough up the surface to give it something to bond to. You can machine JB Weld after it cures. I would be concerned using a 5 min or 1 hr clear epoxy that it may crack after time.
<a href=showthread.php?s=&postid=8714277#post8714277 target=_blank>Originally posted</a> by AcroSteve
Well, it ain't pretty, but I accomplished what I needed to. Which was to rebuild the threads to the point of providing additional support to the piece that threads into them.

Here is what I started with. I might have had better results if I had not been overly concerned with gluing the two pices together. I am not sure I needed anything at all on the white pice to keep the epoxy from sticking to it.
http://i11.photobucket.com/albums/a159/sbowman01d/DSCN3519.jpg

http://i11.photobucket.com/albums/a159/sbowman01d/DSCN3524.jpg

You can see some voids in the repair. The mixture was thicker than I had imagined and I did not work it into the nooks and crannies well enough.
http://i11.photobucket.com/albums/a159/sbowman01d/DSCN3525.jpg

This stuff smells just like weldon 40.

But overall, I think This $5 LMI pump will work just fine.

AcroSteve
12/09/2006, 09:20 PM
If you read my 1st post, I said i was using plastic epoxy. It is actually a two part adhesive called "Plastic Welding System"

I called it epoxy to simplify things. Sorry for the confususion, but if you have ever used either the 5 min or 1 hr epoxy, you would see that what is in my picture is not the same.

JB weld would have been a compromise and a lesser adhesive. And I was not interested in machining it after it cured.

NanoReefWanabe
12/09/2006, 09:49 PM
from what i was told pipe dope is not to be used on water lines...as the water will eventually disolve it..

just what i have heard though...i have seen it used on pools before though