JB Weld versus Loctite for grubscrews

[fafrd]

No, but in retrospect I should have. After reading Arthur Eld's postings on helicoils, I realized that a) the tapped holes on the cells were even less deep than I thought, b) using drill bits and taps that were tapered made them shallower. The first terminal I did I ended up snipping off a part of the helicoil that extended above the holes surface due to this. The resulting thread did torque to specs and is holding. Taht said, on the second terminal of that same cell I measure the length of the screw thread of the bolts provided with the cells and drilled carefully down to that depth before inserting the second helicoil - something I would not have even considered had this cell not be quite damaged already during shipping.

Meaning that a standard 1/4” drill bit allowed you to drill down 5mm without piercing the bottom of the cell?

What about the stock Helicoil Tap? We’re you able to use a stock Helicoil Tap without modification and did it allow you to tap a full 5 threads without piercing the bottom of the cell?

If so, I’d be very interested to see a picture of the stock Helicoil tap (and/or stock Helicoil kit) you used - if there is any way to avoid grinding bits and taps for an acceptable solution (~45 inch-lbs of torque), that would be a major simplification...

The resulting thread/helicoil process went fine and holds great - and it didn't appear I got anywhere near going trhough the terimnal into the cell itself.

How many 1mm threads do you believe you have tapped and what level of inch-lbs have you torqued the repaired terminals to?

Also, did you use a drill press to drill your holes?

And finally, for this second terminal, did you also need to trim the Helicoil before inserting or were you able to use a stock Helicoil without modification?

 

[Hedges]

The drill for a helicoil is basically the bolt diameter - if threads strip out you probably don't even need to drill, you just tap the hole. It is a larger diameter but same pitch as the original threads, and it restores the original threads but in steel.

Nothing wrong with just using the original aluminum threads. By avoiding wear/galling (probably by using loctite on a grub screw), you should be OK if you stay within specified torque.

If you do strip the threads, either over-torque or because they were tapped badly by the vendor, you can easily put in helicoils.

I think we've now had reports of both success and failure using JB weld to put a grub screw in a stripped hole. Not clear what was different between the two experiences. But if it fails, easy enough to jack it out and go to helicoil.

I think the key is having experience using a torque wrench, recognizing if it is holding firmly vs. starting to strip, in which case you don't want to put in in service.

 

[fafrd]

The drill for a helicoil is basically the bolt diameter - if threads strip out you probably don't even need to drill, you just tap the hole. It is a larger diameter but same pitch as the original threads, and it restores the original threads but in steel.

I just checked and a standard 1/4” drill bit is too large to fit down the stripped terminal hole (but 4 threads of an M6 grubscrew slip in and out with ease).

If you think the Helicoil tap can be used in that existing stripped M6 hole without needing to drill it slightly bigger (1/4”) or deeper (5mm), that would be a big simplification.

Also, if I use the existing stripped M6 hole as a guide, I can probably get an M6 drill bit and drill down another 1mm without needing to worry about a drill press...

Would be fantastic to understand how many Helicoil threads others have successfully installed and what level of torque they are successfully applying...

Arther Eld has tested to 45 inch-lbs (or was it 55 inch-lbs) but he set the ‘gold standard’ in terms of grinding a 1/4” drill bit to flat, drilling down to a full 5mm, and grinding a Helicoil tap to flat before using it to tap a full 5 threads.

I’ve got a 4mm stripped M6 hole and would love to understand what I could hope to achieve using a standard Helicoil tap (with or without drilling a deeper h

Nothing wrong with just using the original aluminum threads. By avoiding wear/galling (probably by using loctite on a grub screw), you should be OK if you stay within specified torque.

Yes, Loctite Red’ed-in or JB Welded-in, unstripped threads have been shown by both Arther Eld and myself to withstans

If you do strip the threads, either over-torque or because they were tapped badly by the vendor, you can easily put in helicoils.

I think we've now had reports of both success and failure using JB weld to put a grub screw in a stripped hole. Not clear what was different between the two experiences. But if it fails, easy enough to jack it out and go to helicoil.

From what I have seen, anyone who has successfully used JB Weld to recover a truly stripped thread has not applied anywhere near 35 inch-lbs of torque.

Now to be fair, my stripped terminal is only 4mm deep, so if those other JB Weld ‘success stories’ involved stripped terminal holes which were 5mm deep or more, that would probably impact the outcome (but still hard for me to believe they are torquing more than 25% above the 20 inch-lbs where my 4mm JB Welded grubscrew pulled out - meaning 25inch-lbs).

I think the key is having experience using a torque wrench, recognizing if it is holding firmly vs. starting to strip, in which case you don't want to put in in service.

Agreed.

 

[cinergi]

My EVE 280's are measuring 7mm+ deep. One of them is stripped so I'll be doing this soon. I do have a cheap drill press but in lieu of that you can use something like https://www.amazon.com/gp/product/B00J3ZYEJQ/
I have a bottoming tap but even that won't put threads all the way down. I may cut off the tip of a 1/4" bit and possibly the tap, too. I'll do a video on it ... watch my channel (I'll never remember which thread to post the results in lol)

 

[ArthurEld]

As I await delivery of cells, I may be overthinking this Helicoil option again after reading so many post about damaged threads. I had planned to only insert Helicoils in my new, virgin threads before adding the M6 grub screws. I have always "assumed" that I did NOT have to drill out the original threads with a larger bit AND I did NOT have to tap the hole to accept the Helicoil and then my M6 grub screw. Is this true?

I don't think you need to use Helicoils unless you strip a thread.
Especially if you just plan to put the battery together and leave it alone.
I think most people have problems from tightening and loosening a lot.
Also, if you have solid busbars, only adjust the fixture when the cells are fully charged and with the busbars loose.
Otherwise you will put a lot of side pressure on the screws.

 

[Sillyputty]

Meaning that a standard 1/4” drill bit allowed you to drill down 5mm without piercing the bottom of the cell?

Please note that this is something I probably wouldn't do if the cell weren't already damaged in shipping. I went down to almost 10mm and only on the second terminal and only because I could not get the full helicoil into the first terminal. Since this was the anode (negative) I gradually saw a copper-colored metal as I carefully drilled deeper. It's my understanding that the cathode (positive) terminal is all aluminum, and that the negative terminal (anode) gradually becomes copper or copper alloy as it gets closer to the battery pouches/structure itself.

We’re you able to use a stock Helicoil Tap without modification and did it allow you to tap a full 5 threads without piercing the bottom of the cell?

Reminder: this is the second terminal I'm referring to. I did use the stock tap, which isn't a bottoming tap and is tapered, so it worked to the extent that I went to 8mm (the depth I drilled) it didn't pierce the cell itself (as far as I could tell). I was then able to get the full helicoil into the hole.

How many 1mm threads do you believe you have tapped and what level of inch-lbs have you torqued the repaired terminals to?

Since I drilled to approximately 10mm it would be less than that due to the taper on the tap, so perhaps 6-7 complete threads - enough for the unmodified helicoil to seat firmly.

Also, did you use a drill press to drill your holes?

No - just carefully using a portable drill.

The kit I used - the extent I drilled/taped marked in tape on the tap - and the original bolt and helicoil used.

 

[zzyzx]

If you use Loctite Red to secure stainless grubscrews into your virgin threads, there is absolutely no need to mess around with Helicoils (unless you’ve convinced yourself that you absolutely need more than 45 inch-lbs of torque on your busbars/lugs).

Right . . . I had planned to use Loctite Red with the grub screw IN the helicoil, but now will just use the Loctite Red with the grub screw on the virgin threads . . . AND watch the torque!

 

[fafrd]

I don't think you need to use Helicoils unless you strip a thread.
Especially if you just plan to put the battery together and leave it alone.
I think most people have problems from tightening and loosening a lot.
Also, if you have solid busbars, only adjust the fixture when the cells are fully charged and with the busbars loose.
Otherwise you will put a lot of side pressure on the screws.

That’s a very good point. I used my bundled bolts with a quick and dirty Busbar
composed of 2 pieces of 12AWG copper on each + and - terminals to top-balance my new cells.

The M6 bolts were only ‘hand-tightened’ with a Philips screwdriver, but the fully charged cells did ‘accordion out’ at the bottom, so there must have been some stress applied to the terminals...

This may have contributed to the terminal that stripped (in addition to having only 4 threads engaged and probably some galling...).

 

[Hedges]

Helicoil for M6 x 1.0 thread calls for 6.2mm tap.
0.1 mm per side of hole isn't much. I expect the taper tap to cut its way in, especially for soft aluminum.
Use suitable fluid. Back off periodically to clear chips, maybe back out and blow out.
Because it is a shallow hole, good to grind tap end flat as "bottoming" to thread full depth. So need two if you plan to strip any more.

HeliCoil | HeliCoil Drill Sizes | HeliCoil Drill Chart | HeliCoil Specs | HeliCoil Data | HeliCoil Inserts | HeliCoil Screw Thread Inserts | HeliCoil Thread Repair Kits | HeliCoil Tools | Recoil

www.thorintl.com

 

[fafrd]

Please note that this is something I probably wouldn't do if the cell weren't already damaged in shipping. I went down to almost 8mm and only on the second terminal and only because I could not get the full helicoil into the first terminal. Since this was the anode (negative) I gradually saw a copper-colored metal as I carefully drilled deeper. It's my understanding that the cathode (positive) terminal is all aluminum, and that the negative terminal (anode) gradually becomes copper or copper alloy as it gets closer to the battery pouches/structure itself.

It’s my anode that is stripped as well. It’s currently only 4mm deep but you’re making me feel I could drill down at least another 3mm / 3 threads.

How many Helicoil threads did you get engaged in the first terminal (how much Helicoil did you have to cut off) and what level of torque have you tested in that shallower Helicoil repaur

Reminder: this is the second terminal I'm referring to. I did use the stock tap, which isn't a bottoming tap and is tapered, so it worked to the extent that I went to 8mm (the depth I drilled) it didn't pierce the cell itself (as far as I could tell). I was then able to get the full helicoil into the hole.

Do you know what ‘full length’ your Helicoils are (and how many threads engaged)?

Since I drilled to approximately 8mm it would be less than that due to the taper on the tap, so perhaps 6-7 complete threads - enough for the unmodified helicoil to seat firmly.


No - just carefully using a portable drill.

The kit I used - the extent I drilled/taped marked in tape on the tap - and the original bolt and helicoil used. View attachment 38215

Great - thanks. That looks like a 10-thread / 10mm Helicoil but it would be great if you could confirm.

Also, I believe I read somewhere that the Helicoil can continue to engage into the tapered part of the hole, just getting too narrow for the M6 threads of a bolt to follow.

Have you tried to gently thread that bolt without washers, lugs, or busbars into both terminals to see how many 1mm M6 threads will engage with the Helicoil?

 

[Hedges]

Also, I believe I read somewhere that the Helicoil can continue to engage into the tapered part of the hole, just getting too narrow for the M6 threads of a bolt to follow.

Issue with that would be, because this isn't a solid insert but rather just a coil spring, any tension applied to the bolt would only be carried by the corresponding threads in aluminum. You do want full depth engagement of the bolt (or rather grub screw.) I think Arthur said he was able to screw it all the way in, but I think that was with just a slight taper remaining on the tap after he ground it down.

 

[fafrd]

Helicoil for M6 x 1.0 thread calls for 6.2mm tap.
0.1 mm per side of hole isn't much. I expect the taper tap to cut its way in, especially for soft aluminum.
Use suitable fluid. Back off periodically to clear chips, maybe back out and blow out.
Because it is a shallow hole, good to grind tap end flat as "bottoming" to thread full depth. So need two if you plan to strip any more.

HeliCoil | HeliCoil Drill Sizes | HeliCoil Drill Chart | HeliCoil Specs | HeliCoil Data | HeliCoil Inserts | HeliCoil Screw Thread Inserts | HeliCoil Thread Repair Kits | HeliCoil Tools | Recoil

www.thorintl.com

One tapered bit to start the threads and then the second ‘blind hole’ tap to square threads to the bottom of the hole?

McMaster apparently sells blind hole taps for Helicoil, so I have to decide if I want to experiment with my first-ever grinding of bits on these expensive taps or if I should just purchase one manufactured for that purpose.

Also, I’d really like to know how many Helicoil threads are necessary to withstand 45 inch lbs.

4 M6 threads in stainless are probably enough, so the question is really whether 4 Helicoil threads in Aluminum can withstand that amount of torque.

If I can get to 45 inch lbs using standard bits/taps with no grinding involved and the most complicated part being ore-trimming the Helicoil, that would be my strong preference...

 

[Maast]

I gotta say, the more I read about you guys mucking about with JB Weld and Helicoils - the more I think "I'm sticking with Keenserts". Its what we use at work when we have to fix a stripped bolt hole in aluminum and they always work perfectly. A bit more expensive but the cost is minor compared to everything else.

 

[Sillyputty]

That looks like a 10-thread / 10mm Helicoil but it would be great if you could confirm.

It's 8mm before insertion. (Note: I edited the previous comment to reflect 10mm, not 8mm)

"[I feel] I could drill down at least another 3mm / 3 threads."

My thought process was this: The bolts they ship have approximately 10mm of threaded length. This cell is already damaged badly - I'm going to drill that deep and see what happens. It worked out OK (so far) but was quite stressful during the process. Your mileage may vary.

Since the entire 8mm helicoil is inserted and the grubscrew is in all the way to the bottom, it used all the available (8?) threads.

 

[Hedges]

I gotta say, the more I read about you guys mucking about with JB Weld and Helicoils - the more I think "I'm sticking with Keenserts". Its what we use at work when we have to fix a stripped bolt hole in aluminum and they always work perfectly. A bit more expensive but the cost is minor compared to everything else.

May be good.
Are they short enough to be installed flush?
You will really need flat-bottom drill to get enough depth.
A bit larger, loses some contact area but maybe not much.
With steel thread and solid construction, OK without engaging bolt to full depth.

I've used them. I figured if they were good enough for certain, uh, "aerospace" applications, they were good enough for automotive.

4 M6 threads in stainless are probably enough, so the question is really whether 4 Helicoil threads in Aluminum can withstand that amount of torque.

I doubt it. The aluminum is much weaker than steel or stainless.
6 thread will be 50% more.

 

[ArthurEld]

It's 8mm before insertion. (Note: I edited the previous comment to reflect 10mm, not 8mm)



My thought process was this: The bolts they ship have approximately 10mm of threaded length. This cell is already damaged badly - I'm going to drill that deep and see what happens. It worked out OK (so far) but was quite stressful during the process. Your mileage may vary.

Since the entire 8mm helicoil is inserted and the grubscrew is in all the way to the bottom, it used all the available (8?) threads.

Don't drill 10mm deep

 

[fafrd]

Issue with that would be, because this isn't a solid insert but rather just a coil spring, any tension applied to the bolt would only be carried by the corresponding threads in aluminum. You do want full depth engagement of the bolt (or rather grub screw.) I think Arthur said he was able to screw it all the way in, but I think that was with just a slight taper remaining on the tap after he ground it down.

I understand that - it’s more the simplicity of being able to use unmodified bits/taps as well as unmodified Helicoils.

If you can get a stock 6mm Helicoil completely threaded and only 5mm of M6 threads engage a grubscrew, I’m pretty certain that will take 45 inch-lbs of torque.

4 M6 threads into aluminum might not take 35 inch-lbs but since 5 M6 threads do, 4 M6 threads probably take at least 28 inch-lbs and since the Helicoil threads are larger than M6, 4 of them out to take more than 28 inch-lbs.

The stock Helicoil bottoming taps taper over two threads, so if you drill to 7mm and use that bottom tap, you should be able to get a full 6mm Helicoil threaded out of which at least 5 threads of M6 grubscrew should engage.

5 full threads of grubscrew in Helicoil and Helicoil in terminal should easily withstand 45 inch-lbs (from what I’ve experienced).

And I’m glad I didn’t use a 1/4” bit, that’s 6.35mm or 2.4% larger than 6.2mm. Is the stock Helicoil bit 6.2mm?

 

[Sillyputty]

Don't drill 10mm deep

I encourage this, too, but it's too late for me. Did you?

 

[fafrd]

It's 8mm before insertion. (Note: I edited the previous comment to reflect 10mm, not 8mm)



My thought process was this: The bolts they ship have approximately 10mm of threaded length. This cell is already damaged badly - I'm going to drill that deep and see what happens. It worked out OK (so far) but was quite stressful during the process. Your mileage may vary.

Wow, 10mm. Not that it’s recommended to drill that deep, but very good to know what the limits are...

Since the entire 8mm helicoil is inserted and the grubscrew is in all the way to the bottom, it used all the available (8?) threads.

It sounds like the 10-turn helicoil measures 8mm as a solid spring and expands to 10mm once threaded into the terminal.

Since your M6 bolt has 10 1mm threads, are you able to fully thread it (without washer or other intermediary) or dies is stop turning after 8 or 9 turns?

 

[ArthurEld]

I encourage this, too, but it's too late for me. Did you?

Hopefully I misunderstood.
Drilling 10mm deep might result in death