JB Weld versus Loctite for grubscrews

fafrd

Solar Addict
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...
 

ArthurEld

Photon Sorcerer
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.
 

fafrd

Solar Addict
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...
 

ArthurEld

Photon Sorcerer
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.
 

fafrd

Solar Addict
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)?
 

ArthurEld

Photon Sorcerer
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.
 

Hedges

Photon Sorcerer
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.
 

fafrd

Solar Addict
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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ArthurEld

Photon Sorcerer
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
 

fafrd

Solar Addict
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...
 

ArthurEld

Photon Sorcerer
‘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.
 
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