Helicoil Repair

[vdotmatrix]

The closer I look at that bolt the more it looks like the threads are fine (?) but just packed with aluminum from the stripped hole it came out of.

Exactly true….

 

[vdotmatrix]

You may very well be able to tap the hole for an M6.5; rather than Helicoil or Timesert, both of which will leave less parent material.

Except the valve cover bolt is dedicated to this application.

 

[vdotmatrix]

In my opinion, repairing the first time with a Heli-coil allows future option for a repair with a solid insert. Most of us don't keep stuff long enough to see iteration #2 but it is a nice "defense in depth" option.

I am the original owner of this 1980 cx-500c.

 

[whateg01]

I am the original owner of this 1980 cx-500c.

Could have been slightly over tightened each time and finally fully pulled the threads out

 

[vdotmatrix]

Why do those boots have such a sharp point?

Boots or bolt?

 

[vdotmatrix]

I went back and re-read every post so far. This head has never leaked oil. The two bolts only go in so far before they tighten and can go no further. I wonder if I used a driver to put the bolts back and had it on an unnecessarily high torque setting by mistake. Anyway, this is a very low torque application. I will have to research how much meat I need for each flavor of repair: helicoil or Timesert. This is stressing me out. If it were a muffler or kick stand, I wouldn't care, but this is in a 45 year old bike‘s cylinder head where one more fkup will be a big headache.

 

[whateg01]

Boots or bolt?

Would that be a stripper bolt?

 

[Rusted Nut]

I went back and re-read every post so far. This head has never leaked oil. The two bolts only go in so far before they tighten and can go no further. I wonder if I used a driver to put the bolts back and had it on an unnecessarily high torque setting by mistake. Anyway, this is a very low torque application. I will have to research how much meat I need for each flavor of repair: helicoil or Timesert. This is stressing me out. If it were a muffler or kick stand, I wouldn't care, but this is in a 45 year old bike‘s cylinder head where one more fkup will be a big headache.

Aluminum head with steel bolts? Galvanic corrosion.

 

[vdotmatrix]

Aluminum head with steel bolts? Galvanic corrosion.

Really? The helicoil is stainless isn’t?

 

[david3921]

Boots or bolt?

Pretty sure he meant bolts because I had the same question when I saw them. Maybe the bolts puncture a new gasket for better sealing?

BWT, that's a pretty clean looking 45 year old engine.

 

[CapriMikeC]

M6 x 1 Helicoil will require a 6.3mm drill. https://www.mcmaster.com/91732A782/

"Thin" wall keylocking insert requires an 8.8mm drill. https://www.mcmaster.com/93715A610/

Do the Helicoil first. If galling is a concern, use the nitronic version. https://www.mcmaster.com/93914A247/

 

[PCustoms]

Boots or bolt?

Pretty sure he meant bolts because I had the same question when I saw them. Maybe the bolts puncture a new gasket for better sealing?

Yes, bolts.

I've never seen anything with such a sharp cone point.

 

[Rusted Nut]

Really? The helicoil is stainless isn’t?

I was referring to the existing bolt.

 

[Snip's]

Why do those bolts have such a sharp point?

More than likely, its a cost saving step by the manufacturer... Thread forming bolt...
I have several on my MINI Cooper aluminum rear trailing arm suspension...
Holes are cast smooth without threads being tapped...
Point on the bolt helps automated equipment locate the hole prior to insertion and forming the threads...
In the previous year MINI, the trailing arm was steel using a pre threaded hole and a normal bolt...
The switch to aluminum trailing arms brought about a re-engineered cost saving step using thread forming bolts...
As can be imagined, it's pretty important the automated equipment have the correct torque setting, to prevent thread stripping...

 

[PCustoms]

More than likely, its a cost saving step by the manufacturer... Thread forming bolt...

I thought about that, and if that's the case this is likely the cause of the OP issue.

I've used/specified a few for various materials. Everything I've come across (that I remember) has a modified thread (i.e. trilobe, hi-low etc) or a groove (though that's more thread cutting). I can't recall anything with a sharp point tip and standard machine threads.

If these were "forced" (as designed) then it clearly creates some weak threads.

 

[RoninB4]

I thought about that, and if that's the case this is likely the cause of the OP issue.

 

[KnurledNut]

M6 x 1 Helicoil will require a 6.3mm drill.

6.25 is preferable for aluminum.
6.3 for steel, magnesium, plastic.

 

[rust in the eye]

Oh yes….but it shave the aluminum so evenly….

Typical thread shearing off. This didn't happen upon tightening. Thermal expansion of dissimilar metals combined with what was likely an overtightened fastener did.
I have a small collection of these aluminum slinkys from BMW engine blocks after overheating

 

[MJD1]

I used to think that, until I did some testing to discover that I had better luck with the Helicoil's in general. I used to build a lot of 2-stroke and VW engines and did a lot of in-house side by side comparisons back in the 90's and I had multiple Timeserts pull out where the Helicoil's continued to hold well past their "normal" fastener size torque applications.

Not my experience.

 

[Wamsutta]

Keenserts

 

[vssjim]

I was referring to the existing bolt.

Honda uses chrome plated steel bolts in valve covers a lot

 

[Shannon Boal]

Part of the pullout problem is depth of the threads. (Thread depth rule of thumb; one and one-half diameters, but more with aluminum). I drill the hole full depth plus all I can get at the helicoil tap drill size. Then I tap it and follow up with a helicoil tap with the end ground off (homebrew bottoming tap). Then I count how many turns on the tap coming out so I can custom cut my inserts. I end up with the depth of a helicoil plus, say, four and one half extra threads. I cut a helicoil with dikes to give me four threads, set it in the bottom of the hole, break the tang with a pin punch and blow it out with compressed air. Then I set an (uncut) helicoil on top, break and remove tang. The top end of the top helicoil should seat about one half thread down in the hole. Three things about this...1).it costs more.....2)if you make the top coil too long, grab it with needle nose before breaking the tang and wind it out of the hole..3)leave a third of a turn between the top of the bottom coil and the bottom of the top coil so you can precisely locate the depth of the top coil. The extra depth makes it very pullout resistant. Oh, bright light and a magnifier for this stuff....

 

[vdotmatrix]

This kit arrives today. I suppose there isn't much of a rush now since there is snow on the ground, wo if i need a high quality kit, i have time. The helicoil brand was not available, that i could find in Amazon, without a long wait. This had decent reviews.
I measured everything so I could plan for every contingency.

 

[Shannon Boal]

This kit arrives today. I suppose there isn't much of a rush now since there is snow on the ground, wo if i need a high quality kit, i have time. The helicoil brand was not available, that i could find in Amazon, without a long wait. This had decent reviews.
I measured everything so I could plan for every contingency.

So, you could get two diameters (12mm) of threads engaged, and be quite a bit stronger than the original threads.....which lasted a long time.

 

[whateg01]

My only beef with the Amazon kits like that is the tang doesn't always like to break of easily like on a real helicoil. Otherwise, they seem to work ok for me.

 

[vdotmatrix]

So, you could get two diameters (12mm) of threads engaged, and be quite a bit stronger than the original threads.....which lasted a long time.

I was just reading your post earlier. Interesting. There is only 14mm of usable thread….i have to see what i get with this inexpensive kit I ordered from amazon…

 

[vdotmatrix]

My only beef with the Amazon kits like that is the tang doesn't always like to break of easily like on a real helicoil. Otherwise, they seem to work ok for me.

Ye, i cannot afford to mess this up and i am already seeing who carries the Helicoil brand. I don’t want to say , “you get what you paid for in this case”.

 

[Steve_P]

The last time I had an emergency and needed a helicoil kit NOW, my local Car Quest had it in stock. I think the standard thread length of the insert is about one diameter, which is plenty for something like a valve cover, since it also works on exhaust manifolds. McMaster sells them in various lengths if you want to go crazy.

 

[KnurledNut]

Ye, i cannot afford to mess this up and i am already seeing who carries the Helicoil brand. I don’t want to say , “you get what you paid for in this case”.

I wouldn't personally use that Amazon kit.
If you can't source Helicoil brand then the Fix-A-Thred inserts and tooling (Howmet Aerospace brand) available at auto parts stores are good quality.
https://www.hfsindustrial.com/us/fix-a-thred-repair-kit.html

 

[vdotmatrix]

I wouldn't personally use that Amazon kit.
If you can't source Helicoil brand then the Fix-A-Thred inserts and tooling (Howmet Aerospace brand) available at auto parts stores are good quality.
https://www.hfsindustrial.com/us/fix-a-thred-repair-kit.html

I have spent a lot of time reading reviews, one common issue with the helicoil brand is the tang breaks off…it does not come with a drill bit matched to the kit scary…. Thank s for helping…fretting!

 

[whateg01]

I have spent a lot of time reading reviews, one common issue with the helicoil brand is the tang breaks off…

I've only had the tang break off on a helicoil brand once. The good thing is you can use a pick to pull the top of the wire out and grab it with needle nose pliers and just pull it out. The Amazon one has the opposite problem. It usually pulls the bottom turn out of the tapped thread before it breaks off. Pretty easy to use a pick to put it back but I can see where sometimes it might not be.

it does not come with a drill bit matched to the kit scary…. Thank s for helping…fretting!

You can look up the drill size.

 

[vdotmatrix]

I've only had the tang break off on a helicoil brand once. The good thing is you can use a pick to pull the top of the wire out and grab it with needle nose pliers and just pull it out. The Amazon one has the opposite problem. It usually pulls the bottom turn out of the tapped thread before it breaks off. Pretty easy to use a pick to put it back but I can see where sometimes it might not be.


You can look up the drill size.

$30. I guess i can use a 6.3mm bit or a 1/4” bit.

 

[SMOKEYBEAR]

I went back and re-read every post so far. This head has never leaked oil. The two bolts only go in so far before they tighten and can go no further. I wonder if I used a driver to put the bolts back and had it on an unnecessarily high torque setting by mistake. Anyway, this is a very low torque application. I will have to research how much meat I need for each flavor of repair: helicoil or Timesert. This is stressing me out. If it were a muffler or kick stand, I wouldn't care, but this is in a 45 year old bike‘s cylinder head where one more fkup will be a big headache.

I was going to ask if you ran it on/ off with electric impact/ ratchet tools. They do have an effect on fasteners coming out of aluminum, learned that myself even after reading the precautions from MagHytec on a transmission pan. Didn't think a 12 volt Milwaukee non Fuel ratchet spun with enough speed or force, but sure enough it cost me 2 holes on an E4OD transmission. They would hold just tight enough not to fall out or leak.

Good luck on your repair.

 

[CJM8515]

bet you, like all hondas with similar 6mm bolts the torque spec is 6 foot pounds, in other words choke up on a 1/4 drive ratchet and just snug it!

i would personally go to 1/4" bolt if I could find one that works. or a 7mm allen head bolt.

 

[Shannon Boal]

Looking at the original photo, I count eight or nine threads pulled out. Nine threads at 1.0 mm, makes one and one half diameters engaged. In steel, that woulda been OK, in aluminum the longer the better.

 

[Steve W.]

Some time ago, I purchased this kit:

https://www.amazon.com/gp/aw/d/B07MZQK1HP/?tag=atomicindus08-20

It has been a life saver.

.

 

[Wamsutta]

I like these kits that are size specific. That's right, this whole kit is one single size.

 

[Steve_P]

Looking at the original photo, I count eight or nine threads pulled out. Nine threads at 1.0 mm, makes one and one half diameters engaged. In steel, that woulda been OK, in aluminum the longer the better.

How much thread engagement do you need for an 18-8 SST or grade 2 equivalent M6 screw threaded into 6061-T6 so that the screw breaks before the threads strip?

 

[rlitman]

How much thread engagement do you need for an 18-8 SST or grade 2 equivalent M6 screw threaded into 6061-T6 so that the screw breaks before the threads strip?

It depends on the depth (i.e. percentage) of thread engagement.

 

[vdotmatrix]

I should have never tried doing this. I apparently didn't drill the hole deep enough. A disaster in so many levels as I see it.