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Old 10-27-2020, 01:42 PM   #1
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Shurflo 4048 water pump stripped screw threads

My Pentair Shurflo 4048 water pump stopped working and started leaking when the 4 corner screws came loose and a couple of the 4 inner screws came loose. See the exploded diagram below. All the screws are #10-32.

I tightened the screws and got by for the rest of my trip, but the screws started to come loose again, so I disassembled the pump to see what was going on. I found that the pump comes with a bizarre approach to the housing screws that is simultaneously flimsy and overbuilt.

The 4 corner screws only go a short distance into the motor housing, even though there is room for a longer threaded screw. I tapped it out and put in longer screws, but my problem now is that the loose operation stripped the top left screw in the housing. I put on Loctite blue to hold it, and it came loose. I put in more Loctite blue along more thread length, and I'll see what happens. But, I suspect it will fail. I have 3 choices for the repair and would be interested in the experience of others with this problem:
1. Drill out the hole and thread it with a #12-32 screw and Loctite Blue. Hopefully there is enough room that I don't damage any other parts like the diaphragm.
2. Use Loctite Red or Green. That will hold, but will be impossible to undo unless I heat it. Heat would damage the plastic housing and diaphragm. That gets expensive.
3. Install some sort of backer on the pump housing to allow for a nut on a longer screw, or glue in a backer to allow for the hole to be extended and more threads to be cut for a longer screw.

Have people encountered this and how did they approach the problem?

The problem arises because Shurflo only lets the screw bite on about 1/8" of thread. That's OK if it is a hardened nut, but not enough for the cast housing.

It looks like Shurflo has dealt with a similar problem with the 4 inner screws, which go into backing plate to sandwich the rubber diaphragm. When these screws loosen, the whole pump leaks water. And, those screws also only go into about 1/8" of metal. Shurflo recognized the problem of these going loose and sealed the threads in with something equivalent to Loctite Red. When I tried to remove these screws, it was very hard (for the ones that hadn't loosened themselves). I ultimately wound up twisting three of the screws and breaking the other. Fortunately, these are the same screws as the 4 corner ones, so I used those in order to get the precisely correct screw length.

Shurflo didn't do a careful job of designing the pump. Allowing for longer threads would have been a simple fix.

–Gordon
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Old 10-27-2020, 01:56 PM   #2
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If this is the original pump, then it worked for about 6 years before failing?
Every unit I have owned had a Shurflo water pump. I've never run into this problem, but I can see how it would happen. They all vibrate tremendously! I usually put mine on a rubber pad that dampens vibration and noise.
I admire your efforts to fix the problem with longer screws and backer plates, but I think you will be fighting a losing battle.
Perhaps it's time to look at replacing it, maybe with a different high flow model. Or perhaps Shurflo has redesigned this model in the mean time.
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Old 10-27-2020, 03:27 PM   #3
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I'd say it's time to replace the old pump. The newer SHURflo 4008 & 4048 Revolution Pumps have corner screws that go all the way through the aluminum mounting flange.
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Old 10-27-2020, 03:43 PM   #4
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I replaced mine 3 years ago with a REMCO water pump with 5.3 gpm capability. Really happy with it!
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Old 10-28-2020, 01:53 PM   #5
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Use this

Fix the stripped thread with one of these. The original brand was Helicoil, but the generic ones are much less expensive. Also available at your local auto parts store.

It surprises me that Shurflo engineers used 10-32 NF machine screws into cast metal. Best practice is to use coarse (e.g., 10-24 NC) threads into cast metal because the fine threads in the grainy casting are easily stripped.

National Coarse (NC) for castings like iron and zinc
National Fine (NF) for malleable metals like steel and brass
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Old 10-28-2020, 05:39 PM   #6
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Larry,
I agree that NC would have been the proper choice of screw thread for the pump. The Helicoil idea looks good. I assume that I have to drill the hole out a bit to make room for it. I guess an alternative would be to wrap some thin wire (or a coil spring) around the screw threads and screw it back in, along with some Loctite.

DW,
I do have the latest model of Shurflo 4048 pump, which is the 4048-153-A75 item in their catalog https://www.pentair.com/content/dam/...rv-catalog.pdf
The catalog picture you have shows the screw going slightly beyond the end of the housing. My screw was likely 1/16" or even 1/8" shorter. It didn't come through the housing. It was about 1/16" short of the end. But, the extra 1/16" of an inch probably wouldn't have been enough. Maybe I had a bad model run.

NMWildcat,
I agree that this is an unusually short life for a water pump. My old trailer had a pump that looked the same (same prefilter, etc), and it was going strong after 20 years.

Edgewant,
The Remco pump could be better. It is rated at 5.3 gallons per minute and the 4048 Pentair is listed at 4 GPM. But, I don't have a problem with low flow. I'd be interested in seeing some reviews and tests of Remco vs Shurflo before investing in a new pump. That makes me inclined to repair my Shurflo, since this seems to be the only flaw in its design, so far.

I've got my coach in storage for the winter, so I won't be able to do the fix until the spring. I was interested in ideas on how to approach the problem when spring does roll around.

–Gordon
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Old 10-28-2020, 06:12 PM   #7
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$60 bucks on Ebay incl shipping!
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Old 10-28-2020, 06:21 PM   #8
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My Shurflo pump is really hard to get to. Only can use one hand and reaching real far. I have short arms. I remounted it a couple years ago quieted it down. this year noticed it was getting noisy again. I used zip ties around base and pump when winterizing. Must be the screws from the base to the pump coming loose. It quieted down again.
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Old 10-28-2020, 07:46 PM   #9
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Quote:
Originally Posted by gordonsick View Post
Larry,
I agree that NC would have been the proper choice of screw thread for the pump. The Helicoil idea looks good. I assume that I have to drill the hole out a bit to make room for it. I guess an alternative would be to wrap some thin wire (or a coil spring) around the screw threads and screw it back in, along with some Loctite.
Gordon,

If you have never used helicoils, this is a great time to learn. The kit comes with a drill bit or specifies which one to use. It also comes with a special tap. The tap is just the right size for the outside of the coil and its thread profile matches the profile of the outside of the coil. Notably, it's smaller than the next-size machine screw (#12 in your case), a significant factor when the hole is in a small ear and a larger hole would weaken the structure.

You re-drill the hole, then tap it with the special tap. The aftermarket units come with a tap handle on the mandrel, or you can use a standard tap handle.

This is the clever part. At one end of the coil, the wire is bent so it forms a diameter, right across its bore. If you were to attempt to screw the threaded insert into place with thumb and forefinger, you would conclude that the tap was undersized or the coil was too big. But when you slide the coil onto the mandrel, you see that the end of the mandrel has a flat or notch that accepts the bent end of the coil. As you attempt to screw the coil into the newly tapped hole, the mandrel winds the coil, tightening it and reducing the outside diameter. The coil is screwed in until the back end is flush. As you release torsion on the mandrel, the coil expands and locks into place. You can turn a screw in and out with no worries about unscrewing the coil. If your project needs to accept a screw that is longer than the insert, just insert the mandrel such that the end-wire is not in the notch, and tap the end of the mandrel. That cross-bore segment will break away at a narrow spot placed during manufacture.

This will be a much more robust fix than Loctite or JB Weld.

Let us know how it comes out.
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Old 10-28-2020, 11:08 PM   #10
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Larry,
Thanks for the explanation. After reading your first post, I did some research. The Ebay link you gave doesn't go well to Canada – $60 shipping charge!

But, I did find an E-Z Lok system on Amazon Canada for $35.71. I think I'll order it, since Amazon Prime should give free shipping. https://www.amazon.ca/Z-SK30620-Thre...N7PYTYPVMZGQFQ

I did find several YouTube discussions of these things. The most compelling one did some serious testing of various alternative systems and the helical insert systems were actually strong enough to break the bolt before they stripped.

–cheers, Gordon
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Old 10-29-2020, 06:45 AM   #11
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I just replaced ours with a SeaFlow 3 GPM pump. The SureFlow kept losing prime. So far it works like a champ.

We use it mostly for flushing the toilet when we stop for a potty break on the side of the road, most of our camping is in state parks and have water available.

https://www.campingworld.com/seaflo-...mp-118493.html
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Old 10-29-2020, 09:20 AM   #12
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Impressive test

Quote:
Originally Posted by gordonsick View Post
Larry,
Thanks for the explanation. After reading your first post, I did some research. The Ebay link you gave doesn't go well to Canada – $60 shipping charge!

But, I did find an E-Z Lok system on Amazon Canada for $35.71. I think I'll order it, since Amazon Prime should give free shipping. https://www.amazon.ca/Z-SK30620-Thre...N7PYTYPVMZGQFQ
Gordon,

That was an impressive test. (Some systematic error? All of them failed on the left side first.)

I saw several Ez-Lok offerings on US Amazon, with and without the drill bit. That seems to add $8-10 to the price. Please let us know how it comes out.

I have used these on some pretty serious repairs including the central drive shaft bearing mount on the 1962 Impala.
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Old 10-29-2020, 02:37 PM   #13
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Things are warming up next week and my coach should be sufficiently thawed to allow me to remove the pump without damaging the hoses.

It seems that these helical coils are used by a lot of manufacturers on their OEM factory products where threads go into soft castings. This explains why they are sold in bulk. That makes me inclined to repair all 8 of the screws on my pump.

I'll let you know how the installation goes, but I won't be able to really test the results until the spring.

–Gordon
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Old 10-29-2020, 08:22 PM   #14
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Forgot to mention

Quote:
Originally Posted by gordonsick View Post
Things are warming up next week and my coach should be sufficiently thawed to allow me to remove the pump without damaging the hoses.

It seems that these helical coils are used by a lot of manufacturers on their OEM factory products where threads go into soft castings. This explains why they are sold in bulk. That makes me inclined to repair all 8 of the screws on my pump.

I'll let you know how the installation goes, but I won't be able to really test the results until the spring.

–Gordon
Gordon, one thing I forgot to mention is that most of the 10-32 helical coils I looked at were 3/8" (0.375") long. I know you said the casting wasn't bored very deep. You may have to deepen the hole. If you need to leave it blind, you can cut the top off flush with the surface. The Dremel might be best for this.
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Old 10-30-2020, 10:02 AM   #15
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Larry,
All of the holes are open at the back, so I won't have a problem with a long coil. The 4 holes on the middle of the sides screw into a plate and behind the plate is the housing for the motor. I might have to open up more space on the housing. As you say, a Dremel is a good choice there.

BTW, I see that the original Helicoil comes with three taps that successively lead you to the last bottoming tap. The one I ordered only has one tap, so missing the bottoming tap, which could be a problem if my hole wasn't open at the back.

–Gordon
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Old 11-28-2020, 04:51 PM   #16
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The Short Story of Shurflo Pump Repair with Heli-Coil

I ran into some problems with my repair strategy and then was sidetracked by the gig economy. But I finally got back to my Shurflo pump repair. Here, I’ll give the short story for someone facing the same problem but having little interest in the details, perhaps because they will just buy another pump or hire someone to do the repair.

I used a Heli-Coil thread repair kit to repair the threads on my Shurflo pump. In my view, this is an upgrade, rather than just a repair, as I now have a stronger and more reliable pump assembly on what is otherwise a good, high-volume water pump.

If I were to just replace the pump with a new Shurflo pump, I’d be stuck with the same poorly engineered 10-32 thread system for fastening the Pump Head to the Motor. That would leave me at risk to having the threads strip again, while I’m boondocking away from a water supply and away from a shop where I can get parts.

I could go for another brand of pump, but I’d want to see some credible reviews of the other pump versus a Shurflo to be sure I wouldn’t be buying another bundle of problems. The Remco 55AQUAJET-ARV looks interesting and is reasonably priced at $209, even though it has a higher flow rate than the Shuffle 4048. It is available at https://www.rvupgradestore.com/Aquaj.../aquajetrv.htm However, looking at the pictures of the pump head, it looks like it also threads Torx screws into a motor casting like the Shurflo. It could have the same stripping problems, although it looks like it uses 8 screws rather than 4 screws to fasten the head to the motor, which would be better than the Shurflo. And, from the Ramco pictures, it looks like I could fix stripped threads by just drilling the holes longer and putting nuts on the ends of the screws, since the back end of the housing is square to the screw.

There is a review article of water pumps at https://www.rvtalk.net/best-rv-water-pump-reviews/ that lists 15 pumps on the basis of price and performance. Shurflo pumps are #1, 6 and 9 on the list. The Shurflo 4048 is listed at #6, presumably because of its price, because it is the highest-volume Shurflo on the list. Shurflo parts are readily available on the internet, but the RVTalk review suggests that “Quality control still leaves things to be desired” in its review of the Shurflo 4048. The Remco Aquajet-ARV is #11. It looks like the big hit on the Remco is the price.

Overall, I think my Shurflo repair will work reliably. But, if I have more problems with it, I will take a closer look at the Remco 55AQUAJET-ARV.

–Gordon
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Old 11-28-2020, 05:05 PM   #17
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Repairing stripped 10-32 screw threads with a Heli-Coil and similar repair systems

I bought an E-Z Lok SK30620 Helical Threaded Insert Kit from Amazon Canada at https://www.amazon.ca/gp/product/B00...?ie=UTF8&psc=1 since it had all the tools needed for the installation, plus 10 threaded inserts. The first picture below shows what it supplied with the kit.

I decided to test the kit out on a 0.18” thick piece of aluminum before committing myself to the Shurflo pump repair. My initial test went poorly. After drilling the hole and threading it with their STI 10-32 tap (which is larger than a regular 10-32 tap, since it must provide room for the helical coil), I screwed in a 10-32 screw. The screw was really tight and the installation actually stripped the threads on the screw. I tried again, and now the installation pulled out of my aluminum stock.

This drove me to investigate the source of the problem. I found the following issues:

• My installation technique could have been faulty (more on this below, because I only diagnosed the problem last).

• The thread pitch on the E-Z Lok STI 10-32 tap was not exactly 32 TPI. I couldn’t figure out the exact pitch, but it didn’t match that on any SAE or Metric taps that I had and I tried a pitch gauge at 24, 27, 28, 32, 36 and 40 tpi and none matched. When I held a 10-32 screw against the tap, they seemed to be usably close for 3/16”, but deviated enough after that that peaks were hitting peaks on one end and valleys on the other end. It might be that E-Z Lok intended a pitch with an interference fit for more tightness.

• The E-Z Lok came with a 13/64” drill bit, which is 0.203125”. The original inventor of these systems, Heli-Coil recommends a smaller #7 drill, which is 0.201” for aluminum. (That is slightly larger than a 3/16” drill, which is 0.1875”.)

• The wire on the E-Z Lok coil has a round cross section, which doesn’t fit well into the v-shaped thread groove from the tap. In contrast, the Heli-Coil inserts have a diamond-shaped cross section, which does embed nicely into the v-shaped thread grooves. The second picture below shows the Heli-Coil inserts.

So, I ordered Heli-Coil inserts at https://www.amazon.ca/gp/product/B00...9W4873PK&psc=1 and used them with my E-Z Lok tool kit.

I used the Heli-Coil inserts with the E-Z Lok tap after drilling a #7 hole. Everything went together nicely in my test piece of aluminum. The 10-32 screw goes in tightly, so it is pushing the coil out into the threads of the aluminum, making it stronger than if I simply tapped a screw with a standard tap and screwed it into the aluminum. This makes the installation tighter.

Of course, it could be that the interference between the thread pitches is making the fit tight, but over a thickness of 0.18”, I don’t think the interference would be significant.

When using the Heli-Coil insert and the E-Z Lok tap, I was able to tighten a 10-32 screw as hard as I could with two hands and nothing stripped out. I used a square-drive #2 (Robertson) screw driver for the best possible drive and I was starting to mangle the drive head without stripping threads. The same amount of force would have easily stripped the hole if I put a 10-32 or 10-24 hole with proper threading but no insert.

Interestingly, I went back to retest the E-Z Lok inserts after my success with the Heli-Coil inserts and they also worked fine, since I couldn’t strip the threads, just as I couldn’t strip them with the Heli-Coil. Perhaps my installation technique was better. The biggest change that I made to my installation technique was to properly set the stop on the E-Z Lok installation tool so that I could use the stop to push the coil insert properly against my aluminum piece. This squared things up properly and might have been why the installation worked differently. The technique is clearly shown in the installation video at https://m.media-amazon.com/images/I/C1-pY7oecES.mp4 The third picture in the next post also shows how the collar pushes up against the insert to align the installation properly.

Heli-Coil has a variety of on-line documentation, and they have a very informative catalog at http://www.noblefix.com/PDF/Helicoil...-Catalogue.pdf. Page 16 of that catalog recommends a #7 drill (0.201”) for their STI tap if going into aluminum and a 13/64” drill (.2031”) if going into steel, magnesium or plastic.

If I were doing the job from scratch again, I’d probably order the Heli-Coil kit https://www.amazon.ca/Helicoil-5528-...ct_top?ie=UTF8 to be sure that I was getting the correct thread pitch on the tap, and also getting the diamond-shaped cross section on the coils.

Comparing the two companies, Heli-Coil is now a subsidiary of Stanley and is the originator of this thread repair system. The E-Z Lok company is also a pretty significant company. They did a lot of strength testing of their products at https://www.ezlok.com/testing. So, I’m not so sure that E-Z Lok is a bad company to work with.
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Old 11-28-2020, 05:08 PM   #18
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Repairing my Shurflo 4048 stripped threads

After my testing and development, as discussed in the previous thread, I decided to go to work on my Shurflo pump. The mounting flange from the motor is a non-ferrous casting that could be either aluminum or pot metal. The material strips easily. It would be better if the original design used larger screws with a thread pitch of 20 or 24 tpi.

I used a #7 drill to drill out the holes on the four corners of the flange, as shown in the first photo below. I used a drill press and a support to hold the pump steady and square. Note how the mounting holes are in a nipple boss extension that gives a total of 0.355” of thread length for the repair. If I just drilled the holes out for a bigger #12 or #14 screw, I would have significantly weakened those nipples. In the same photo, I have one coil insert already installed in the corner opposite to the one into which I was drilling. Also, note that I covered the motor shaft with some duct tape to keep it from getting fouled by metal chips.

Next, I tapped the holes with the E-Z Lok STI 10-32 tap, as shown in the second photo below. Note how I held everything square in a vise, being careful to avoid deforming the motor housing.

The third photo shows how the coil inserts are installed into the tapped hole. The installation tool has a collar that allows you to press up against the coil, while aligning it to go properly into the hole. (The installation problems that I discussed in the previous post may have come from not using the collar to hold the coil in place accurately.) The installation tool has a slot to hold a tang at the end of the coil. This slot and tang arrangement allows you to turn the coil into the threads. The tang is broken off with a punch, after the coil is installed. Just install the coil to be flush with the top of the nipple, even though the coil isn’t long enough to go all the way to the other end of the hole. When you install the screw into the coil, the coil turns more deeply into the housing, so give it some room to run by leaving the extra threads at the back.

The fourth photo shows the pump head installed onto the motor flange. Note how I used a blue thread-locking glue to help the screws stay in place, despite the vibrations from the pump action. (Blue thread locking glue can be removed, but I’d need a 1/4” impact wrench to do it. Red thread locking glue is harder to remove and requires heat, which would be bad for the pump diaphragm.) Also, note how the screw nearest to the camera had its coil run out of the hole a bit. That is why you want to just insert the coils just enough to be flush with the top of the nipple. They do get turned in farther as the screw is installed.

The four installed screws went in very tightly and I used both hands on a #2 square screw driver for the installation. That much torque would have stripped the threads in the original installation without the coil inserts. That is why I think that this is an upgrade rather than just a repair. The system is stronger and more reliable because of the coil inserts.

Finally, I want to discuss my original plan to upgrade the other 4 screws that are in the midpoints of the sides of the motor head. These 4 screws do not go into the mounting flange, but just into the Drive Assembly plate, which is Item 4 in to exploded parts diagram of the very first post in this thread. This plate holds the diaphragm and valve assembly in place. It is not subject to the pumping forces of drive motor, but it does help to hold the water pressure, since it holds the diaphragm in place. My earlier repair to the pump used blue thread locker on these screws and they still seemed to be well in place. So, I decided not to do the thread repair on these. The four outer screw holes that I replaced also assist these screws to hold the water pressure, so they are not heavily stressed as long as the outer screws don’t fail.

–Gordon
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Gordon Sick, Calgary
2015 Berkshire 34QS
The Manual I wrote for our 34QS:
https://www.forestriverforums.com/fo...qs-191578.html
Toad: 2019 Ford Ranger XLT 4x4; Formerly: 2005 Acura EL (aka Honda Civic)
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Old 11-28-2020, 08:39 PM   #19
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Join Date: Jan 2018
Location: Raleigh, NC
Posts: 3,395
Glad to hear that this worked out for you. Thanks for informing me that only Heli-Coil has a true diamond-cross section on their coils.
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Larry

Sticks and Bricks: Raleigh, NC
2008 Cherokee 38P: at Ivor, VA permanently
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Old Yesterday, 03:02 PM   #20
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Join Date: Mar 2015
Location: Calgary
Posts: 820
Other Sources of Diamond Cross Section Helical Inserts

Larry,
While the Heli-coil insert has a diamond-shaped cross section, it isn’t the only one. Uxcell also has a diamond shaped cross section and is reasonably priced in bulk. https://www.amazon.ca/uxcell-10-32x0...940911&sr=8-10

If you are buying a coil system, try to look at the the coils or photos of the coils. Amazon lets you blow up their photos. If you are in a store looking at the coils and have eyes that are more than 50 years old, seeing the diamond shape can be hard. But, if you turn the coil in a strong direct light, you might be able to see the extra brightness when you turn it so that is reflecting off the flat edge.

–Gordon
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Gordon Sick, Calgary
2015 Berkshire 34QS
The Manual I wrote for our 34QS:
https://www.forestriverforums.com/fo...qs-191578.html
Toad: 2019 Ford Ranger XLT 4x4; Formerly: 2005 Acura EL (aka Honda Civic)
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