I wish I understood the wildly different experience you're having from my own. I'm trying to think of the differences ... I wonder if it's the taps themselves? I suppose it could be technique? I started with a normal bit (not a bottoming bit) -- maybe that's it? I don't know ...
JB Weld versus Loctite for grubscrews
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ArthurEld
Solar Wizard
You need to back up the tap often to clear the chips. Otherwise you will mess up the threads.
I was doing that, but perhaps more frequently and not as far back. Rather than backing off a quarter turn every half-turn, I was probably backing off an eight-turn every quarter-turn. On my next attempt I will follow that video. He also used quite a bit more oil than I did...
I think I will also keep the thread guide in place the entire time this next go-round, rather than only using it to get started and then going freehand,
ArthurEld
Solar Wizard
You will be able to feel how far to back up. Stopping and backing up makes the chips shorter. And backing up farther breaks the chips free from the tap.
I don't think you should start the tap freehand. You should start the tap in the drill press.
I don't think you should start the tap freehand. You should start the tap in the drill press.
I also started with the tapered bit. On fact, that went well-enough that I may have gotten overconfident. The tapered bit backed-out pretty-easily, but when I switched to the bottoming bit, that’s when things started going awry.
I may just also be less-coordinated than you
.I think next try I will plan to use the tapping guide most of the way down. Part of the issue was also that removing the tap was more difficult with the tapping guide in place.
If I continue to have difficulty removing the tap, I may exchange this Helicoil kit for another one, though it’s also possible I wasn’t backing-up enough to ‘break off the chips’ so this just may be a compounding of many little things.
Next try:
- more tapping oil
-back off full 1/4 turn after each half-turn
-secure clamping guide to aluminum bar with clamps to assure it cannot move while tapping
-more carefully confirm original 15/64” drilled hole is square/straight before I start tapping
-tap straight through to the end (after switching from tapered tap to bottoming tap) without ‘checking halfway’.
The good news is I’ve got plenty of Aluminum and Helicoils to practice / learn with...
I can try that again as well, but from my first try using the drill press to start the tap with the tapered tap, the mass and bulk of the drill press dramatically overwhelmed the soft aluminum terminal. On the way in, everything went fine, but trying to back the tap back out was a nightmare. I think if I let up of the handle, it would have ripped the tap right out.
I could ‘feel’ the appropriate force to get the tap to bite going in, but found it impossible to judge how much push or pull to provide when getting the tap to back out.
I suppose leaving the tap engaged and loosening the chuck is another option I could try...
ArthurEld
Solar Wizard
The reason you are having trouble is because you didn't drill the hole to 1/4"
I
Move the cell with the tap still in to someplace that you can finish tapping by hand.
I
You need to push on the handle and turn the chuck by hand about two turns. Then loosen the chuck to release the tap.
Move the cell with the tap still in to someplace that you can finish tapping by hand.
That’s a good point. Both you and Cinergi used a standard 1/4” hole and I should probably practice with that hole size tomorrow. I had the bright idea to use a smaller holesize closer to the ID of the tap, but that may have been a mistake...
I’ll try that as well. I’m not sure I have enough play to lift the chuck off of the tap, but I can give it a try.
Are you suggesting to stop tapping with the tapered bit after two turns and before bottoming and then continue tapping with it by hand until I’ve bottomed, or bottom with the tapered bit in the press then remove tapered bit from chuck and remove tapered bit from hole and continue tapping with bottoming tap by hand?
ArthurEld
Solar Wizard
I think it was worth a try but it didn't work. So drilling to 1/4" makes sense. Do you have a flat bottom drill?
Yes you should practice. You can have the key in the chuck and use it for leverage to turn the tap. Then when you need to loosen the key you don't have to let go of the handle with your other hand.
I'm saying forget the tapered tap.
Drill the hole to 1/4"
Then start the flat bottom tap on the drill press like I said above.
Finish it by hand. Use oil and back up a lot.
ArthurEld
Solar Wizard
You don't need the tapered tap because the flat bottom tap has some taper and the end has a chamfer that is made to cut.
And because the terminal is soft. The tap is brand new it should cut perfect.
You need to get two full turns on the drill press because you can easily tip the flat bottom tap otherwise. Three turns is good too. But you will have to back up a couple times.
And because the terminal is soft. The tap is brand new it should cut perfect.
You need to get two full turns on the drill press because you can easily tip the flat bottom tap otherwise. Three turns is good too. But you will have to back up a couple times.
Also, I’ve discovered how much the Helicoil compresses to additional turns/threads once threaded.
My standard 6mm Helicoils have 7 full turns from tang bending in to start of coil and have ~6-5/6ths turns to where the tang snaps off (meaning 6 full coils under the starting point after the tang has been snapped off.
After insertion, I’ve got pretty much 2 complete coils extending out of the threaded hole and can see 7 full threads from the start of the Helicoil to under that spot (so 5 threads in the hole out of the 7 threads that were there before, after exposed coils are subtracted).
And from where the tang broke off, there are now ~7-1/2 coils/threads to the top (meaning ~4-5/6ths coils have now compressed to ~5-1/2 coils now.
So it looks like I have about 5-1/2 coils threaded out of what was originally 4-5/6ths coils and I will plan on removing a total of two full (uncompressed) cools for my final insertion into the terminal,
Compressing 4-5/6ths coils to 5-1/2 coils corresponds to a ~14% compression (or increase in the coil count).
My standard 6mm Helicoils have 7 full turns from tang bending in to start of coil and have ~6-5/6ths turns to where the tang snaps off (meaning 6 full coils under the starting point after the tang has been snapped off.
After insertion, I’ve got pretty much 2 complete coils extending out of the threaded hole and can see 7 full threads from the start of the Helicoil to under that spot (so 5 threads in the hole out of the 7 threads that were there before, after exposed coils are subtracted).
And from where the tang broke off, there are now ~7-1/2 coils/threads to the top (meaning ~4-5/6ths coils have now compressed to ~5-1/2 coils now.
So it looks like I have about 5-1/2 coils threaded out of what was originally 4-5/6ths coils and I will plan on removing a total of two full (uncompressed) cools for my final insertion into the terminal,
Compressing 4-5/6ths coils to 5-1/2 coils corresponds to a ~14% compression (or increase in the coil count).
Yeah, since I’m running into these difficulties, I should try drilling the same (standard) 1/4” hole everyone else uses...
I don’t have a flat-bottom bit and honestly, I’m not feeling the need. I got 5-1/2
Wise suggestion - thanks!
Gotcha. One of my attempts tomorrow will be exactly this approach...
Any reason not to go as far as I can in the press?
Hedges
I See Electromagnetic Fields!
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- Mar 28, 2020
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Drill press as guide for tap wrench:
ArthurEld
Solar Wizard
It's just easier with the tap handle once it's started. But it won't hurt to go as far as you can. You have to keep pressure on the handle all the time.
Well, I just successfully inserted my first Helicoil.
Got all set to drill a hole with the 1/4” bit when it occurred to me to check that the platform on my press was level. It was side-to-side (which is the direction it can be adjusted). Since I had the right angle there I thought I’d check the front-to-back angle as well, and surprise of surprises, it is off of a perfect 90 degrees.
Probably means this press is worthless and probably also means my terminal is toast (since I drilled by hand using this press), but on with my saga.
I wanted to use the tapping guide to drill a straight hole and since my tapping guide is metric, I couldn’t use the 1/4” bit so returned to the 15/64” bit (which fit pretty snugly in the 6mm guide hole.
Ended up needing to use the power drill but got a nice straight hole drilled, a bit over 7mm, like the hole in my terminal.
Started to tap using the tapered tap and the tap guide and got about 2 full turns done.
First, I used tapping oil this go-round, and second, I followed the suggestion to back off 1/4-1/2 turn after every half-turn. The chip was wedging at about 1/4 turn back, and so by pushing past that to 1/2 turn back, I finally know what it feels like to snap off the chip - in all past attempts, I was backing off only until that point and then worried that I was gouging out the threads I’d just tapped, so I’d continue forward.
Aside from issues with my holes not being straight, I think this is the single most important thing I was doing wrong.
After removing the tapered tap, I switched to the bottoming tap, still through the tap guide. I continued with the bottoming tap until I started to feel the resistance increase, at which point I removed the tap (without cross-threading for the first time ever!), cleaned out the hole and inspected.
I saw nice, clean threads but it looked like there was more untouched cylinder at the bottom of the hole than I saw in yesterday’s attempt so I rethreaded the tap (this time without the tap guide) and got about another full thread tapped by using more force.
Got the tap removed cleanly and counted five full threads down from the top with space for at least one more thread below the last thread that was clearly-tapped.
Cleaned out the hole and decided to try my 6-coil Helicoil (reduced from 7 originally).
Got the Helicoil threaded and it just barely sunk below the surface (with a bit of force - the bottom of the coil started pressing against the insertion tool again).
Like last time, I snapped off the tang by just increasing the insertion force until it snapped. The slot in the insertion tool is once again compressed and squeezing the tang, as well as a visible thread mark at the bottom where the lower-most coil was compressed against it.
I first threaded an M6 bolt and it engaged for a full 4-1/2 threads up to a force of 50 inch-lbs. I then replaced with a grubscrew which engages for a full 4 threads including the tapered end which I may file off.
Allen head in the hex head of the grubscrew looks straight (orthogonal to the aluminum rod) and when I finger-tighten a brass nut on a large lug, I can’r see light on either side and cannot slip a piece of paper in-between. So I think the grubscrew is straight.
I can go to 50-ft lbs on that nut without issue, so 4 threads engaged is more than enough.
Now that I know what tapping is supposed to feel like and I know the 15/64” hole diameter is not an issue, I’m tempted to just go ahead and try to tap the terminal using the same technique.
Again, the hole is probably not straight but reasons it might be is that I used the existing hole (which was presumably straight) to guide down the 15/64” but by hand, which was essentially just reaming out the remaining JB Weld stick against the sidewalls.
So I figure I’ve got nothing to lose. But I’m going to hold off for a day in case any of the helpful crew here have any advice for this tapping neophyte.
Also, since my current process relies so heavily on the tapping guide, I’m going to have to rig up some sort of structure with a bottom board below the cell and clamps to assure that the guide stays fixed/solid on the tiny terminal surface while I’m tapping down...
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Things I am worried about with my process:
-A lot of force being applied to get the Helicoil all the way seated down to the point that the 6th coil disappears into the hole and then the tang snaps off going forward - any risk of this much torsional force causing damage near the bottom of the terminal?
-I can get 4-1/2 threads of an M6 bolt engaged into what appears to be 6 threads, so I believe it is bottoming out into the tapered threads at the bottom and not coming into contact with the bottom of the hole - any way to be sure?
-And same question with the grubscrew - it seems to be bottoming-out a half-turn before the bolt but has a tapered end extending 0.5-1mm below the deepest thread - I’m pretty sure it’s not bottoming but it would be nice to be certain (and I may file the end square just to be safe).
I’ve noticed the the grub screw loosens a bit when I loosen the nut, so if I’m not going to use Loctite, I feel like I should use an Allen Head to keep the grubscrew from loosening.
And I’ve also noticed that if I tighten to 35 inch-lbs, loosen (with Allen Head wrench to prevent grubscrew turning) and then tighten to 35 inch-lbs again, the grub screw advances a bit more each cycle.
So I kind of feel like I should use Loctite Red to keep the grubscrew affixed, but I can be careful and use an Allen Head wrench when loosening as well as tightening if that is a safer path...
Also, I’m wondering if I should try installing a 4-coil Helicoil and removing the tang the ‘standard’ way (in reverse) before finalizing my decision on how many coils to install into the cell. Of course, with one coil less, the possibility of bottoming the grubscrew is increased.
-A lot of force being applied to get the Helicoil all the way seated down to the point that the 6th coil disappears into the hole and then the tang snaps off going forward - any risk of this much torsional force causing damage near the bottom of the terminal?
-I can get 4-1/2 threads of an M6 bolt engaged into what appears to be 6 threads, so I believe it is bottoming out into the tapered threads at the bottom and not coming into contact with the bottom of the hole - any way to be sure?
-And same question with the grubscrew - it seems to be bottoming-out a half-turn before the bolt but has a tapered end extending 0.5-1mm below the deepest thread - I’m pretty sure it’s not bottoming but it would be nice to be certain (and I may file the end square just to be safe).
I’ve noticed the the grub screw loosens a bit when I loosen the nut, so if I’m not going to use Loctite, I feel like I should use an Allen Head to keep the grubscrew from loosening.
And I’ve also noticed that if I tighten to 35 inch-lbs, loosen (with Allen Head wrench to prevent grubscrew turning) and then tighten to 35 inch-lbs again, the grub screw advances a bit more each cycle.
So I kind of feel like I should use Loctite Red to keep the grubscrew affixed, but I can be careful and use an Allen Head wrench when loosening as well as tightening if that is a safer path...
Also, I’m wondering if I should try installing a 4-coil Helicoil and removing the tang the ‘standard’ way (in reverse) before finalizing my decision on how many coils to install into the cell. Of course, with one coil less, the possibility of bottoming the grubscrew is increased.
Looks like even if my hole is a bit off square that there may be a way to salvage that cell after all: https://www.mcmaster.com/washers/leveling-and-wave-washers/metric-leveling-washers-7/
