Helicoils in Cell Terminals

[Hedges]

Thanks.

The primer is just acetone, right?

I can clean the aluminum threads, the Helicoil, and the grubscrew in Acetone before threading the Helicoil into the terminal and then apply Loctite Red before threading the grubscrew, will that work?

Acetone's just the carrier.
Read the MSDS.

 

[fafrd]

You can use the 15/64" hole but you will only get 4 threads of helicoil.

why do you say that? The hole is currently 7.5mm deep in the center and 6.5mm deep on the sides. I think I can get a full 6-7 threads tapped and thought you said the Helicoil will thread into even the tapered threads.

Or are you saying I’ll only be able the thread the grubscrew into 4 threads of the Helicoil?

That I can believe - that the grubscrew won’t fit into the lowest most-tapered threads.

But you convinced me that if I get a grubscrew engaged with 4 threads of Helicoil threaded into a properly-tapped terminal, it’ll be at least as strong as the original unstripped aluminum threads, right? That’s all I’m aiming fir

It is possible to remove the helicoil and drill deeper. Then follow the existing threads deeper with the tap.

Interesting option - so drilling a bit deeper win’t damage the already-tapped threads?

But, as I have said before, I think 3 or 4 threads of helicoil is good for 50 inch lbs or more

Yeah, that’s what is remember you saying. So if I can get the 6-thread Helicoil fully-threaded and the grubscrew only threads by 3 or 4 threads, I should be OK.

You can loosen the chuck with the tap still in the hole. Then remove the cell from the drill press and use the tap handle to continue tapping to the bottom.
I wouldn't do it any other way but there are other ways.

Yeah, that’s what I was planning - how many threads would you advise to complete in the press before removing the tap and continuing by hand (I’ve never tapped anything before)?

You can cut off threads after the helicoil is installed. The dykes will cut the terminal some too but not enough to hurt anything.

With a hole ~7-1/2 mm deep (~6.5mm on the sides), do you think I’ll have any issue fully-threading a 6-full-thread Helicoil (which they would probably call a 5-thread Helicoil since it was sold as 6-thread before I removed the last full ring/thread)?

I don't think loctite is necessary and it could cause problems.

What problems do you think Loctite could cause?

My main reason for wanting to use Loctite is to avoid having to use an Allen head wrench when loosening a nut, but that’s not the end of the world and I think I don’t need to be too concerned about needing an Allen Head wrench when torquing (especially if I leave the tang at the bottom of the Helicoil).

Thanks for all your help and advice.

 

[fafrd]

Acetone's just the carrier.
Read the MSDS.

Got it - thanks. Is primer neeed for the Loctite Red that requires no primer?

Isn’t is a good idea to clean Aluminum threads, Helicoil, and grubscrew in Acetone regardless?

 

[ArthurEld]

why do you say that? The hole is currently 7.5mm deep in the center and 6.5mm deep on the sides. I think I can get a full 6-7 threads tapped and thought you said the Helicoil will thread into even the tapered threads.

I am going by my experience. I put in 4 helicoil threads because that was the most I could get in there.
My holes are as deep as yours. If you get more threads in there that's great. But not necessary.

Or are you saying I’ll only be able the thread the grubscrew into 4 threads of the Helicoil?

The grub screw will go in about 6 turns and will be touching all of the threads.

That I can believe - that the grubscrew won’t fit into the lowest most-tapered threads.

But you convinced me that if I get a grubscrew engaged with 4 threads of Helicoil threaded into a properly-tapped terminal, it’ll be at least as strong as the original unstripped aluminum threads, right? That’s all I’m aiming fir

It will be stronger than original

Interesting option - so drilling a bit deeper win’t damage the already-tapped threads?

A 15/16" drill bit would be better and you have to try not to tear up the existing threads too much. You need to put the drill bit in the hole until it touches the bottom and tap the trigger a couple times on low speed. Then look at it.

Yeah, that’s what is remember you saying. So if I can get the 6-thread Helicoil fully-threaded and the grubscrew only threads by 3 or 4 threads, I should be OK.

I think it will. The grub screw needs to be all the way in or 1/2 turn from the bottom max.

Yeah, that’s what I was planning - how many threads would you advise to complete in the press before removing the tap and continuing by hand (I’ve never tapped anything before)?

I would get it started about 2 or 3 turns.

With a hole ~7-1/2 mm deep (~6.5mm on the sides), do you think I’ll have any issue fully-threading a 6-full-thread Helicoil (which they would probably call a 5-thread Helicoil since it was sold as 6-thread before I removed the last full ring/thread)?

The tap only cuts on the sides so it will only go in about 6mm. You have to be very careful with the tap because they break easy and they are hard to get out once broken.

What problems do you think Loctite could cause?

The grub screw won't turn because the taper on the threads will cause the grub screw to be tight.
The loctite is unnecessary. It probably won't hurt anything if you use it. But I didn't use loctite.
The problem is that you will have unnecessary loctite all over everything.

My main reason for wanting to use Loctite is to avoid having to use an Allen head wrench when loosening a nut, but that’s not the end of the world and I think I don’t need to be too concerned about needing an Allen Head wrench when torquing (especially if I leave the tang at the bottom of the Helicoil).

As I said above, you won't need the allen wrench. I would highly recommend that you take the tang out. You want the screw to engage all of the helicoil threads. Otherwise it won't be as strong. It will tear out if you only engage 1 or 2 helicoil threads.

Thanks for all your help and advice.

No problem.
If I ever have to do it again, I will cut the helicoil so it has 4 threads. then it will go in deep enough so the helicoil is 1/2 turn below the top of the terminal. And it will be stronger than the original threads

 

[Hedges]

Got it - thanks. Is primer neeed for the Loctite Red that requires no primer?

Isn’t is a good idea to clean Aluminum threads, Helicoil, and grubscrew in Acetone regardless?

Acetone is a good solvent to remove oils so loctite works.
According to their literature, primer not needed for primerless products.
Even with regular loctite, Not needed for "Active Metals" (stainless is "inactive")

Iron Plain Steel Copper Brass Bronze Manganese MonelTM KovarTM

https://dm.henkel-dam.com/is/content/henkel/MRO_TL_Guide

 

[fafrd]

I am going by my experience. I put in 4 helicoil threads because that was the most I could get in there.
My holes are as deep as yours. If you get more threads in there that's great. But not necessary.

There are two tapered taps, the through-hole has 7 tapered threads and the one that is almost bottoming only has 4 slightly-tapered threads (can see shallow thread even on the lowest thread). Was the tap you used before you ground it flat tapered for 4 threads or 7?

The grub screw will go in about 6 turns and will be touching all of the threads.

It will be stronger than original

That’s all I need to hear.

A 15/16" drill bit would be better and you have to try not to tear up the existing threads too much. You need to put the drill bit in the hole until it touches the bottom and tap the trigger a couple times on low speed. Then look at it.

If I need to go any deeper, I’ll do it by hand in the press (no motors/triggers).

I think it will. The grub screw needs to be all the way in or 1/2 turn from the bottom max.

I would get it started about 2 or 3 turns.

Exactly the advice I was seeking - thanks.

The tap only cuts on the sides so it will only go in about 6mm. You have to be very careful with the tap because they break easy and they are hard to get out once broken.

OK, so stop when I feel it bottom and the resistance increases. Got it.

The grub screw won't turn because the taper on the threads will cause the grub screw to be tight.
The loctite is unnecessary. It probably won't hurt anything if you use it. But I didn't use loctite.
The problem is that you will have unnecessary loctite all over everything.

OK, I’ll try it first without Loctite.

As I said above, you won't need the allen wrench. I would highly recommend that you take the tang out. You want the screw to engage all of the helicoil threads. Otherwise it won't be as strong. It will tear out if you only engage 1 or 2 helicoil threads.

My thinking was that the tang is below the last thread where the threads are most tapered and also acts as a stop to prevent the grubscrew from reaching the bottom of the hole. So if I have a full 6 threads in there, I’m thinking I’ll have at least 5 threads engaged with the grubscrew.

And I’m also worried about how much trouble it may be to remove the tang.

I’ll get the Helicoil in and then circle-back before finalizing my decision about the tang.

No problem.
If I ever have to do it again, I will cut the helicoil so it has 4 threads. then it will go in deep enough so the helicoil is 1/2 turn below the top of the terminal. And it will be stronger than the original threads

When I read that, it makes me think I should cut off another 1 or 2 coils. Will look at the tapped hole and decide before threading the coil.

What did you use to cut the coils?

 

[ArthurEld]

There are two tapered taps, the through-hole has 7 tapered threads and the one that is almost bottoming only has 4 slightly-tapered threads (can see shallow thread even on the lowest thread). Was the tap you used before you ground it flat tapered for 4 threads or 7?

Start with the 7 thread taper tap. Get it started in the drill press then take it off the drill press and finish threading it in until you touch the bottom.
Then use the 4 thread taper tap to complete the threads.
You need to be careful to push both handles on the tap handle evenly but lightly. Try not to tip the tap. They don't bend at all.
And you need to carefully feel when you reach the bottom.

If I need to go any deeper, I’ll do it by hand in the press (no motors/triggers).

That would probably work well. The aluminum is very soft and you can basically scrape off the material with the flutes of the drill when you turn the chuck by hand while putting light pressure on the handle.

Exactly the advice I was seeking - thanks.

OK, so stop when I feel it bottom and the resistance increases. Got it.

OK, I’ll try it first without Loctite.

My thinking was that the tang is below the last thread where the threads are most tapered and also acts as a stop to prevent the grubscrew from reaching the bottom of the hole. So if I have a full 6 threads in there, I’m thinking I’ll have at least 5 threads engaged with the grubscrew.

It is simpler to just get 4 threads in and break off the tang. If you got 6 helicoil threads in the hole and you leave the tang you will only have 4 effective threads anyway. And you won't get 6 helicoil threads in without making the hole deeper

And I’m also worried about how much trouble it may be to remove the tang.

Look at the tang before you put the helicoil in. You will know where the tang needs to break off. Pry the tang with something pointy until it breaks. You probably will have to pry it back and forth a couple times before it completely breaks off.

When I read that, it makes me think I should cut off another 1 or 2 coils. Will look at the tapped hole and decide before threading the coil.

I would cut off 2 because 4 threads is strong enough and trying to get more than 4 is more work and more likely to cause problems.
Just do it and be done with it. No sense messing with it longer because that is likely to cause a lot of extra work and not much benefit.

What did you use to cut the coils?

Something like this works well.
It is easier to cut before you but the hilicoil in the hole. But I did cut one successfully after it was in using the same tool.
Look at where the tang will break and cut the threads off so you will have 4 full threads after the tang is broke off.

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[fafrd]

Start with the 7 thread taper tap. Get it started in the drill press then take it off the drill press and finish threading it in until you touch the bottom.
Then use the 4 thread taper tap to complete the threads.

I have only the 4-thread taper bit and I’m glad I asked because I was planning to start with that. A friend has the 7-thread taper but and I will borrow that to start as you are recommending.

You need to be careful to push both handles on the tap handle evenly but lightly. Try not to tip the tap. They don't bend at all.
And you need to carefully feel when you reach the bottom.

After drilling by hand, I think I have an idea of what to expect and how to guide the tap, but thanks.

That would probably work well. The aluminum is very soft and you can basically scrape off the material with the flutes of the drill when you turn the chuck by hand while putting light pressure on the handle.



It is simpler to just get 4 threads in and break off the tang. If you got 6 helicoil threads in the hole and you leave the tang you will only have 4 effective threads anyway. And you won't get 6 helicoil threads in without making the hole deeper

I’m looking at my modified Helicoil now. It was sold as a 6-coil Helicoil and had 7 full threads opposite the bend for the tang (and 6 full threads + 2 half-threads on the side where the first coil starts and the tang is bent towards the center).

I’ve already cut off a full coil, so I now have 5 full threads and 4-full + 2 half-threads.

So if I only tap 5 full threads (less that 6 full threads, I’ll cut off another coil.

Between 4 full threads with tang removed and 5 full threads with tang remaining, I’m not understanding why 4 w/o tang is better. Is it because the grubscrew can pass completely through the Helicoil and better-engage the threads?

Does removing the tang mean not bottoming the Helicoil? (4 coils in 5 threads = possible to remove tang; 5 coils is 5 threads = impossible/difficult to remove tang)?

Look at the tang before you put the helicoil in. You will know where the tang needs to break off. Pry the tang with something pointy until it breaks. You probably will have to pry it back and forth a couple times before it completely breaks off.

I understand where the tang is supposed to break off, but given how much effort it took to saw through a coil, I’m not thinking it’s going to be easy to snap off the tang. Maybe I’ll sacrifice a coil or two to practice.

The tool my kit provided is flat-bottomed and intended to break of the tang bu bending it downwards (out of a through-hole), so I’m not seeing how I’m going to be able to do any ‘back-and-forth’ bending at the bottom of the hole...

Mostly, I’m just not understanding why it is so important to break off the tang (especially if I’m successful at threading all 5 threads in there...).

I would cut off 2 because 4 threads is strong enough and trying to get more than 4 is more work and more likely to cause problems.
Just do it and be done with it. No sense messing with it longer because that is likely to cause a lot of extra work and not much benefit.

OK, so you’d advise me to cut off another ring or two, even if I get a total of 6 threads tapped (the lowest 4 starting to taper).

I’m still not understanding why 4 full coils with tang removed in 6 tapped threads is better than 6 full coils with tang remaining in 6 tapped threads.

Something like this works well.
It is easier to cut before you but the hilicoil in the hole. But I did cut one successfully after it was in using the same tool.
Look at where the tang will break and cut the threads off so you will have 4 full threads after the tang is broke off.

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Thanks.

I used a new hacksaw blade by hand using the coil-end as a guide (so only possible to cut off full coils). It was pretty easy (but took more elbow-grease than I would have expected. I can use that same technique to cut off another coil or two if needed.

Right now, I’ve got 6 full coils from where the tang bends to the center (1 less than the original 6mm coil).

So once I see how many threads I tap, I’ll cut off another one or two.

 

[ArthurEld]

I have only the 4-thread taper bit and I’m glad I asked because I was planning to start with that. A friend has the 7-thread taper but and I will borrow that to start as you are recommending.

The 7 thread taper tap is better if you if you are leaving the hole at 15/64" You might have a hard time starting the 4 thread taper in the undersized hole.

After drilling by hand, I think I have an idea of what to expect and how to guide the tap, but thanks.


I’m looking at my modified Helicoil now. It was sold as a 6-coil Helicoil and had 7 full threads opposite the bend for the tang (and 6 full threads + 2 half-threads on the side where the first coil starts and the tang is bent towards the center).

I’ve already cut off a full coil, so I now have 5 full threads and 4-full + 2 half-threads.

So if I only tap 5 full threads (less that 6 full threads, I’ll cut off another coil.

Between 4 full threads with tang removed and 5 full threads with tang remaining, I’m not understanding why 4 w/o tang is better. Is it because the grubscrew can pass completely through the Helicoil and better-engage the threads?

Because the screw doesn't have threads at the bottom so the screw wouldn't touch the extra thread anyway.

Does removing the tang mean not bottoming the Helicoil? (4 coils in 5 threads = possible to remove tang; 5 coils is 5 threads = impossible/difficult to remove tang)?

You will be able to remove the tang even if you tighten it as far as it will go. You have to pry at it to get it to break.

I understand where the tang is supposed to break off, but given how much effort it took to saw through a coil, I’m not thinking it’s going to be easy to snap off the tang. Maybe I’ll sacrifice a coil or two to practice.

The tang is supposed to have a spot that is partially cut off. That way it breaks easy.

The tool my kit provided is flat-bottomed and intended to break of the tang bu bending it downwards (out of a through-hole), so I’m not seeing how I’m going to be able to do any ‘back-and-forth’ bending at the bottom of the hole...

Mostly, I’m just not understanding why it is so important to break off the tang (especially if I’m successful at threading all 5 threads in there...).

OK, so you’d advise me to cut off another ring or two, even if I get a total of 6 threads tapped (the lowest 4 starting to taper).

I’m still not understanding why 4 full coils with tang removed in 6 tapped threads is better than 6 full coils with tang remaining in 6 tapped threads.

I doubt you will get 6 helicoil threads in the hole. But if you did and left the tang in, the screw would only touch 4 helicoil threads because the screw doesn't have threads on the bottom.
If you only have 4 threads and you leave the tang in the screw is only going to be touching 2 threads and most likely you will tear the helicoil out.

Thanks.

I used a new hacksaw blade by hand using the coil-end as a guide (so only possible to cut off full coils). It was pretty easy (but took more elbow-grease than I would have expected. I can use that same technique to cut off another coil or two if needed.

Right now, I’ve got 6 full coils from where the tang bends to the center (1 less than the original 6mm coil).

So once I see how many threads I tap, I’ll cut off another one or two.

You need to play with a piece of scrap aluminum. That way you can perfect your technique and do it better than anyone.
Then you can make a Resource.

 

[fafrd]

The 7 thread taper tap is better if you if you are leaving the hole at 15/64" You might have a hard time starting the 4 thread taper in the undersized hole.

Got it - thanks. On my way to borrow a friend’s through-hole M6 Helicoil tap.

Because the screw doesn't have threads at the bottom so the screw wouldn't touch the extra thread anyway.

Yeah, I’m only getting 5
threads engaging into the 6 Helicoil threads. I’m considering filing a grubscrew flat but will hold off until I see how things shake out...

You will be able to remove the tang even if you tighten it as far as it will go. You have to pry at it to get it to break.


The tang is supposed to have a spot that is partially cut off. That way it breaks easy.

I see that now - thanks. I’m finally understanding how the tang can be snapped off even near the bottom of the hole.

I doubt you will get 6 helicoil threads in the hole. But if you did and left the tang in, the screw would only touch 4 helicoil threads because the screw doesn't have threads on the bottom.
If you only have 4 threads and you leave the tang in the screw is only going to be touching 2 threads and most likely you will tear the helicoil out.

I’m finally understanding the benefit of removing the tang. I’m going get the tap done and will decide how much coil to use after I see how many threads I have. Also, now that I see where the tang will break off, I’ll have only 5 threads above the snapped-off bottom of the coil (and ~5-3/4 threads from the beginning of the coil.

You need to play with a piece of scrap aluminum. That way you can perfect your technique and do it better than anyone.
Then you can make a Resource.

Let’s not get ahead of ourselves .

But thanks again for all your help - I understand do much more know and have learned so much from you!

 

[fafrd]

Just measured my hole again (by hand and without a caliper, so take these measurements with a grain of salt). The center is 9mm, while the sidewalls are 7mm.

With tapered-end down, I can get 7 full threads of a grubscrew (+ another 0.5mm or so where it tapers.

If I thread my 6-coil Helicoil into the 7 grubscrew threads, the grubscrew bottoms into the tang with another full thread exposed.

Got to get the threads tapped (on my way to pick up that tapered tap now), but it’s looking to me like I will be able to get all 6 coils inserted (5-3/4 after the tang is snapped off...

 

[fafrd]

Not going well. I can’t tell if I’ve ruined the terminal or not but this aluminum is so soft there is not enough of a guide after bottoming the tapered bit.

I can get the near-bottoming tap in now but impossible to keep vertical, so I just ordered a tapping guide and will hope that allows me to tap some usable threads once it gets here...

This aluminum feels softer than clay when confronted with these hard tapping bits, so recovering this terminal may be beyond my pay grade...

 

[schmism]

Not going well. I can’t tell if I’ve ruined the terminal or not but this aluminum is so soft there is not enough of a guide after bottoming the tapered bit.

I can get the near-bottoming tap in now but impossible to keep vertical, so I just ordered a tapping guide and will hope that allows me to tap some usable threads once it gets here...

This aluminum feels softer than clay when confronted with these hard tapping bits, so recovering this terminal may be beyond my pay grade...

I guess you skipped over post #42 that advised how to prevent the very issue your having.

 

[fafrd]

I guess you skipped over post #42 that advised how to prevent the very issue your having.

No, I’d missed that post - thanks for pointing it out.

My drill press doesn’t have the height to hold that spring and then the full tap but on top of the cell.

If I can’t get some proper threads tapped with the tapping guide, I may need to bail and give up on this cell (or try JB Weld one last time in whatever threads I cut).

 

[cinergi]

@fafrd did you perchance watch my video on how to do this?

 

[fafrd]

@fafrd did you perchance watch my video on how to do this?

Yeah, watched the whole thing. I’ll watch it again after the tapping guide arrives on Monday. Between the ‘feel’ drilling the hole deeper by hand and my sense from watching your video, I expected the guide strength/force of the first few threads to be stronger than they were.

I tried the ‘7-tapered-tap-by-drillpress’ then switching to my 4-tapered near-bottoming tap by hand and there was not enough of an existing guide to maintain to the tap vertical.

The aluminum is far softer in the face of the tap than it was to being drilled.

Next I’ll try using the tap guide as you suggested.

Should have practiced on some other aluminum, though I suspect that would have been harder and may not have been that useful in preparing for these soft terminals...

 

[ArthurEld]

No, I’d missed that post - thanks for pointing it out.

My drill press doesn’t have the height to hold that spring and then the full tap but on top of the cell.

If I can’t get some proper threads tapped with the tapping guide, I may need to bail and give up on this cell (or try JB Weld one last time in whatever threads I cut).

Did you rotate the table of the drill press out of the way so you have more room?
The drill press makes it easy to keep the tap perpendicular.

Post a picture of the hole. You will be able to save it.

You still should get a piece of aluminum so you can get used to the process. You have a bunch of extra helicoils.

 

[ArthurEld]

Not going well. I can’t tell if I’ve ruined the terminal or not but this aluminum is so soft there is not enough of a guide after bottoming the tapered bit.

I can get the near-bottoming tap in now but impossible to keep vertical, so I just ordered a tapping guide and will hope that allows me to tap some usable threads once it gets here...

This aluminum feels softer than clay when confronted with these hard tapping bits, so recovering this terminal may be beyond my pay grade...

It sounds to me like you need to put the cell in the drill press. Put the tap in the hole and hold pressure against the handle while turning the chuck by hand.
I don't know why this concept seems to be confusing people but once you do it you will know it is a very simple way.

 

[fafrd]

It sounds to me like you need to put the cell in the drill press. Put the tap in the hole and hold pressure against the handle while turning the chuck by hand.
I don't know why this concept seems to be confusing people but once you do it you will know it is a very simple way.

That’s what I did, and all the way until the tapered tap bottomed,

I then switched to using the near-bottoming tap but there was not enough thread established to guide it.

I’ll see if the tap guide allows me to salvage the thread that’s been started, but the fragility of the aluminum terminal in the face of the hard steel of the tap has caught me by surprise.

I feel like I’m working with wet clay...

 

[fafrd]

Did you rotate the table of the drill press out of the way so you have more room?
The drill press makes it easy to keep the tap perpendicular.

Yes, that’s how I drilled the hole and started the tap. I had no idea the top of the press could rotate like that, so thanks for the tip.

Post a picture of the hole. You will be able to save it.

You still should get a piece of aluminum so you can get used to the process. You have a bunch of extra helicoils.

Yeah, Helicoils to spare.

I’ve done some work with aluminum before and have a sense of how the entire process would feel in typical aluminum. These terminals are far softer than any aluminum I’ve experienced before, so I’m not sure how much learning there is to be had in practicing on harder aluminum...

I almost feel like I should practice in wet clay or wax.