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diy solar

JB Weld versus Loctite for grubscrews

DO NOT grind the tap. It is onley tapered for 2 threads. Yoiu must have a taper for it to cut.
 
DO NOT grind the tap. It is onley tapered for 2 threads. Yoiu must have a taper for it to cut.
Pretty sure the tap that comes with that kit is not the bottoming tap.

The bottoming tap has only 2 tapered threads (and doesn’t need to be ground).

The STI tap has 4 tapered threads and needs to be ground if you want to thread more than 2 or 3 M6 threads...
 
Pretty sure the tap that comes with that kit is not the bottoming tap.

The bottoming tap has only 2 tapered threads (and doesn’t need to be ground).

The STI tap has 4 tapered threads and needs to be ground if you want to thread more than 2 or 3 M6 threads...
If you leave 4 tapered threads the screw will still go in but it will be tight at the bottom. That makes the threads stronger.
You have extra helicoils so I suggest you try it. You can remove helicoils by grabbing the top with needle nose plyers and pulling it out.
It won't damage the threads.
 
If you leave 4 tapered threads the screw will still go in but it will be tight at the bottom. That makes the threads stronger.
You have extra helicoils so I suggest you try it. You can remove helicoils by grabbing the top with needle nose plyers and pulling it out.
It won't damage the threads.
Interesting suggestion.

So you’re saying if I use the standard unmodified tap, I can tap down to the bottom, thread a Helicoil in and see how many M6 grubscrew threads engage.

I can leave the tang in since I almost certainly won’t be able the thread to the bottom of the Helicoil, and if I don’t like the way it’s working, I can back out the Helicoil with a pair of needle nose pliers.

I like the idea, though I think I may need to drill a deeper hole first. My existing hole is only ~4mm deep.

So I probably want to drill down another ~3mm and need to devise whether I should drill out the entire hole to 1/4” or just drill another 3mm deep from the bottom using a 15/64” bit...
 
I'm saying you can grab the top thread of the helicoil and pull it out. It uncoils.
My holes are about 7mm deep.

I did two holes with a tapered tap and I could screw the stud to the bottom of both. It got a little tight at the bottom. So, no loctite needed.
 
I'm saying you can grab the top thread of the helicoil and pull it out. It uncoils.
My holes are about 7mm deep.

I did two holes with a tapered tap and I could screw the stud to the bottom of both. It got a little tight at the bottom. So, no loctite needed.
Cool. And how many M4 threads were you able to engage into that tapered Helicoil?

Also, if you were me (no grinder, no drill press), how would you drill out the hole from 4mm to 7mm, with a 1/4” bit or a 15/64” bit )which can be guided by the existing hole)?
 
The screw went to the bottom. I had 4 threads in there so 4 engaged.

I didn't use the drill press to drill my holes. But I used it to start the tap straight. It is harder to start a tap straight when it has less taper.

I think you better get something that won't allow you to drill more than 7mm deep. If you sink a drill bit into the cell you might have flames shooting in your face. Might be amusing if you are wearing fire fighter gear.
 
I think you better get something that won't allow you to drill more than 7mm deep.

I once got a plastic Jacobs chuck that was supposed to serve as a drill stop. It just slid up the drill.

My suggestion is cut a piece of 1/4" copper tubing and slip over drill bit. Put drill bit in chuck so it protrudes from tubing by desired amount. If it does slip further intro drill chuck it protrudes less - no harm, no foul.

If you sink a drill bit into the cell you might have flames shooting in your face. Might be amusing if you are wearing fire fighter gear.

One day I drove my Saab to my mountain lot, and seat mount broke along the way.
Pulled out my torch to weld it up. Decided I didn't care if the carpet got singed in the process.
Suddenly a fire ring appeared, expanding as it came toward me. When it reached my face it was big enough to go around my goggles. Got a singed mustache among other minor effects.
Under the carpet, I found a plastic gas line, which carries fuel from the 100 psi injection pump in tank under trunk. Had to seal that fuel tight in the field.
I wrapped it with layers of teflon tape, then a split rubber hose and hose clamps.
 
The screw went to the bottom. I had 4 threads in there so 4 engaged.

Wow, so the taper was gentle enough to allow all of first tapered thread to engage M6. You modified a 6 coil Helicoil to make a 4-coil Helicoil, correct? So 4 coil threads engaged into the top 7 tapped threads and the bottom 3 tapered threads remained infilled.

The top 3 Helicoil threads were full-diameter and only the 4th Helicoil thread has slightly reduced thread due to the taper of the tap. And an M6 grubscrew was able to thread through art 4 Helicoil threads including that last tapered thread and reach the bottom.

Very helpful, thanks.
I didn't use the drill press to drill my holes. But I used it to start the tap straight. It is harder to start a tap straight when it has less taper.
So do you think even the standard tapered (4 tapered coil) tap would be hard to tap straight with a press or a jig?

As they say, ‘you only get one chance to tap a straight thread’...

I think you better get something that won't allow you to drill more than 7mm deep. If you sink a drill bit into the cell you might have flames shooting in your face. Might be amusing if you are wearing fire fighter gear.
Yeah, if I drill I will make a stop first. All this DIY stuff is fun, but not worth a trip to the Emergency Room...
 
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Wow, so the taper was gentle enough to allow all of first tapered thread to engage M6. You modified a 6 coil Helicoil to make a 4-coil Helicoil, correct? So 4 coil threads engaged into the top 7 tapped threads and the bottom 3 tapered threads remained infilled.
I didn't get 7 tapped threads. My hole was 7mm deep in the middle. My flat bottom drill went about 6.5mm deep. The tap only went 6mm deep
The top of the helicoil has to go 1/2 turn past. So, I put 4 threads in 5.5mm of tapped threads. And the bottom was defiantly tapered.
The top 3 Helicoil threads were full-diameter and only the 4th Helicoil thread has slightly reduced thread due to the taper of the tap. And an M6 grubscrew was able to thread through art 4 Helicoil threads including that last tapered thread and reach the bottom.

Very helpful, thanks.

So do you think even the standard tapered (4 tapered coil) tap would be hard to tap straight with a press or a jig?
You could use some kind of tap guide but the easiest way for me is in the drill press. I just put the tap in the hole and hold down on the handle while I turn the chuck with my other hand to get a couple threads started. Then the thread axis is perpendicular to the terminal
As they say, ‘you only get one chance to tap a straight thread’...


Yeah, if I drill I will make a stop first. All this DIY stuff is fun, but not wirth
 
I didn't get 7 tapped threads. My hole was 7mm deep in the middle. My flat bottom drill went about 6.5mm deep. The tap only went 6mm deep
The top of the helicoil has to go 1/2 turn past. So, I put 4 threads in 5.5mm of tapped threads. And the bottom was defiantly tapered.

‘Defiantly tapered’ - I like that ;).

Ok, so the tap went down 6mm out of which only the top 2 threads were straight and then two coils were tapered and you succeeded to thread an M6 grubscrew through all 4 coils, right?
You could use some kind of tap guide but the easiest way for me is in the drill press. I just put the tap in the hole and hold down on the handle while I turn the chuck with my other hand to get a couple threads started. Then the thread axis is perpendicular to the terminal
It’s true that the tap is shorter than a drillbit, so I should check whether I can fit a cell under my small HF press with sufficient room for the tap.

No way I could get a 1/4” drillbit ie with enough space to slide a 280Ah cell under it, but a tap, maybe...
 
... small HF press with sufficient room for the tap.

No way I could get a 1/4” drillbit ie with enough space to slide a 280Ah cell under it, but a tap, maybe...


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‘Defiantly tapered’ - I like that ;).

Ok, so the tap went down 6mm out of which only the top 2 threads were straight and then two coils were tapered and you succeeded to thread an M6 grubscrew through all 4 coils, right?

It’s true that the tap is shorter than a drillbit, so I should check whether I can fit a cell under my small HF press with sufficient room for the tap.
I used the cheap HF drill press. You have to rotate the table out of the way and set the cell on the base of the drill press.
No way I could get a 1/4” drillbit ie with enough space to slide a 280Ah cell under it, but a tap, maybe...
I think you can fit a 1/4" drill bit in there. If not you can rotate the whole head off of the base and set the cell on the table.

But I felt more comfortable using the hand drill for the flat bottom drill. I put it in the hole and turned on the drill low RPM. It is easier to start and stop the hand drill. The drill could grab so you need to just tap the trigger. It only needs to rotate a couple times to clean out the corner in the bottom of the hole. I purposely sharpened the flat bottom drill so it wouldn't cut in the middle. That way it would be difficult to drill to deep.

When I used helicoils in machine shops it was always for on the spot repair with a hand drill and hand tap. But we had the full taper on the tap. And we could drill the hole 2" deep.
 
If you use JBweld, Loctite or any other thread glue, be very careful not to get it on the terminal pad..... it will create a slightly resistive barrier that is a bitch to debug. (don't ask how I know that!! ?)

Also, Don't count on any of the thread glue products to add much strength. You can have the best glue in the world... but it will pull out along with the soft aluminum threads.


The next time I purchase cells I am going to investigate having fortune style post laser welded on. I have thought about talking to Amy about it but I don't want to start the conversation if I am not ready to buy. What would be ideal is if she just carried a line of cells with the posts that we could order.
Overkill Fortune cells have very strong stainless posts
 
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)
OK, so I just got one of these, but I figured being a tap to M6 thread, I should get metric.

The shank fits 7mm perfectly but the threads are slightly larger than that and won’t fit through the 7mm hole. The threads fit through the 7.5mm hole but there is enough play that I don’t think it will do the trick.

So now that I’ve understood that you got a Standard tap guide, am I correct that the threads of the M6 Helicoil tap fit snugly into the 9/32” hole?
 
OK, so I just got one of these, but I figured being a tap to M6 thread, I should get metric.

The shank fits 7mm perfectly but the threads are slightly larger than that and won’t fit through the 7mm hole. The threads fit through the 7.5mm hole but there is enough play that I don’t think it will do the trick.

So now that I’ve understood that you got a Standard tap guide, am I correct that the threads of the M6 Helicoil tap fit snugly into the 9/32” hole?
Found the tap specs and the M6 Helicoil tap has a thread diameter of 7.422mm (wish I’d though of looking this up before ordering the tap guide).

This one covers 8/64” to 24/64” in 1/64” increments, but 18/64” = 7.14375mm, smaller than the spec of 7.422mm and 19/64” = 7.54+ mm, larger than the 7.5mm hole I already have that feels like it has too much play.

So what hole size is best for guiding these Helicoil taps? Is 19/64” or 7.5mm the best I can hope for?
 
The helicoil kit I purchased came with an M7 tap and requires a 1/4" drill bit. The resulting threads in the aluminum before the helicoil is M7. After helicoil it's M6 of course.
 
The helicoil kit I purchased came with an M7 tap and requires a 1/4" drill bit. The resulting threads in the aluminum before the helicoil is M7. After helicoil it's M6 of course.
That’s what I expected (and why I purchased a metric tap guide

But the bottoming bit that came with my kit is a bit larger than 7mm (and has too much play in the 7.5mm hole...).

According to this the Helicoil tap for M6 Helicoil is 7.422mm: http://www.noblefix.com/helicoil/HeliCoil-Tapping-Chart.html

So if you Helicoil tap fit through a 7mm guide hole, sounds like it was undersized.

At any rate, by wrapping two layers of masking tape around my tap, I’m comfortable now with the tightness of the fit.

What I’m more worried about now is how to keep it stable on the terminal - seems very borderline.
 
OK, I finally succeeded to tap my first hole in aluminum and install my first M6 Helicoil.

Let’s start with good news first:

A full standard 7-full-turn Helicoil installed all the way down to 1-1/4 threads remaining exposed out the top (so presumably a full 5-3/4 threads engaged.

I can install a standard (flat-bottom bolt to 45 inch-lbs and to takes a full 5-1/2 threads to unthread it from that point (possibly including some portion of the exposed Helicoil, but it seems to be over 4 full threads engaged).

The tang snapped inself off when the Helicoil bottomed and came out within the slot of the tightening tool (easy-peazy).

Now for the bad news.

First and foremost, the thread is not straight. I used the thread guide to form the first 2+ threads and then continued from there freehand, but this end result in a terminal would be worthless.

Secondly, the tapping process was much more difficult than I expected it to be. In general, I felt pretty good about the way I could advance the thread (including backing it off a bit every ~quarter-turn), but when removing the tap, it was not smooth and I’m pretty sure I was catching and removing thread material on the way out as well (and it’s possible this was the reason the thread is not straight).

Minor, but in tightening the Helicoil to the bottom so hard that the Tang snapped off, the slot at the end of the tool deformed (two sides pressed closer together at the end. This should be easy to fix with a screwdriver but indicates how much force is required to get a Helicoil to follow the tapered threads.

I’m going to have to practice this several more times until I can get a straight grubscrew.

My practice Aluminum is an 8” length of 1/2” Aluminum rod. The tapping guide has a long ‘V’ intended to rest on a round surface, so I inverted that to hold the bar while drilling my 15/64” hole in the drill press (by hand) and used it right side up to position the tapered bit while starting to tap.

Lack of being straight from side-to-side I can understand and forgive, but the thread is primarily tilted along the length of the rod, meaning the tapping guide failed to do it’s job.

But my biggest concern is honestly the manner in which the tap caught thread when backing out - I suppose if the thread tapped in along a slight curve, that might exaccerbate that issue, but I feel like this tap wants to tap its way out even more than it wants to tap its way in...

Any advice appreciated - this is all far more delicate and fragile than I expected it to be...
 
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