Can you Loctite Heli-Coil repaired thread?

[Kez]

The front housing bolts in my Picco pre-EXR 45 backed out. Not only did the flywheel get chewed up, the thread became loose. I will need to repair the thread with Heli-Coil.
Question: Can you Loctite the Heli-Coil repaired thread? I use red Loctite and I am not sure if the thread will come out with the bolt.

Thanks k

 

[NITROSNIFER]

I think the best way would be to use green locktite. I would install then remove the insert tool. After it's cured run a tap into it to clean the treads and you'll be good.

 

[brad nichols]

Buy the time you have the coil installed you will be really thin wall. You would be better off to drill and install a standard fine thread bolt by retapping the hole and that would give it more strength.

 

[Bill Gibson]

Buy the time you have the coil installed you will be really thin wall. You would be better off to drill and install a standard fine thread bolt by retapping the hole and that would give it more strength.

I’ve done this very thing to a couple of very old engines and it works very well.

 

[Kez]

Guys,
I was not clear in asking the question. Heli-Coil inserts relies on the coil spring tension to stay in place. I am wondering if I can use red Loctite after repairing the thread. Will red Loctite on the bolt back the insert out?

Metric screws have finer thread than UNC or UNF. Metric screws work well in steel but in my opinion, they strip more easily in aluminum than similar size UNC. 4-40 is stronger than 3mm in my experience.
Thanks, k

 

[brad nichols]

We used red on coil inserts on refiner discs and sometimes the coil came out with the bolt

Brad

 

[Charles Perdue]

The new orange thread loctite holds as well as the red but it releases like the blue when needed, It can be used on aluminum....just a thought.

Charles

 

[Geraghty]

Any loctite can be used......When you decide to take the fastener out just apply 5-10 seconds of heat to the head of the fastener
and the loctite will release .....The screw /bolt will back right out leaving the heli-coil in place......I use a small micro butane torch to heat the fastener.....
https://www.harborfreight.com/butane-micro-torch-63170.htmlhttps://www.amazon.com/Custom-Acces...ble+butane+micro+torch&qid=1594119679&sr=8-43

 

[Charles Perdue]

Mr. Rod is correct, heat does loosen loctite. This is why it is not a good idea to use it on anything that has excessive heat like exhaust bolts.

However if you were to use red loctite on the helicoil and use the orange on the bolt in your application, then it is likely that the helicoil would stay in the engine case.
Just one other way to skin this cat.

Charles

 

[Rudy Formanek]

How about a good condition used crankcase, $15.00 plus 5.00 shipping.

 

[Kez]

Thanks guys for your inputs. I remember seeing a locking insert offered by Heli-Coil. But I am not sure if they can hold the bolts in our engines. I will assemble the engine with Lock-Tite. This is the second time the front housing bolts backed out on me. Each time it happened, the flywheel got chewed up, and the crank bore pitted from the chattering.

Rudy, I will PM you regarding the case

 

[Charles Perdue]

Kez, it sounds as if you have an unusual vibration problem. Maybe flywheel, crankshaft, cable collet, cable, ect.
The internal tooth shake-proof washers work very well with socket head screws for these conditions to prevent the screws from loosening.
Just a thought....

Charles

 

[Kez]

Charles, this P-45 is actually one of the smoother running .45 I have. The Picco flywheel runs very true and so is the cable collet. I am judging by the vibration I feel when I launch the boat.

It may have been me. To avoid stripping the metric thread, I tighten the bolts using the short end of the allen wrench. I would lean on a UNF or UNC bolt a little more as they do not strip as easily.

I have used JB weld and epoxied the front housing to the case before. But that is not possible with the P-45 as the case is trenched for the rod. If I epoxied the front housing I will not be able to remove the rod from the crank.

Thanks, k

 

[Brad Christy]

Kez,

Why not bump up to the next size threads and use larger screws? Form taps are awesome for this. What thread was initially used?

Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine and Precision LLC

 

[Brad Christy]

Kez,

I should clarify....

If you were using 4-40 screws, a form tap will allow you to bump up to M3 screws. M3 screws to 5-40. There are always options, and form taps will allow you to exploit them.

Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine and Precision LLC

 

[Kez]

Brad,
I did not know what a form tap was until I saw your post and looked it up. I have never used one, obviously.
The bolt size is 3mm. And I believe the 4-40 Heli-Coil tape is actually 5-40. Like I mentioned, and I could be wrong, metric threads is stronger (because of the finer pitch) in steel or SS. But they tend to strip more easily in aluminum. UNC like 4-40, 6-32, in my opinion, are better for crankcase. The coarse threads hold up much better in aluminum.
In this case, I have repaired it with Heli-Coil. I think it will last the life of the case.
Thanks, k

 

[Brad Christy]

Kez,

Not exactly...

There is nothing stronger about metric or SAE threads, or fine/course threads. It all comes down to thread engagement ratio (major/minor diameter). On the level you're dealing with, there is really no need to concern yourself with thread strength.

HeliCoil taps are a beast all their own. You cannot use a 5-40 tap for a 4-40 HeliCoil insert. You must use a tap labeled "STI" for the thread size you intend to use.

As for the form tap option.....

The first thing you have to understand about form taps is that the tap drill size is considerably larger than that of a cutting tap of the same thread size. The tap "forms" the material, pushing the "valleys" up onto the "hills", and thus the minor diameter is reduced in the process. If you try and run a form tap into a hole drilled for the same size cutting tap, you will very likely break the tap. Don't. Do. That.

If you are trying to repair M3 holes, you can probably re-tap them for 5-40, just by running a 5-40 form tap into the holes. Fill the holes with WD-40 and make sure the tap gets started straight. You may even be able to get away with not having to open up the through holes in the part you are attaching.

The next size up from there is M3.5 or 6-32, which are basically the same major diameter. The metric screws might be a bit tricky to find, unless you buy a QTY box, but they are a standard size. For the metric tapped holes, you would need to open the hole to .126". I'd suggest a reamer, but you could probably get away with a 1/8" drill. For the SAE thread, I'd suggest a .122" reamer, but I've heard of guys using a 1/8" drill, which I wouldn't suggest. Same process as above for running the tap. You will likely need to open up the through holes of the part being attached.

None of this is unobtanium. MSC has these taps my the thousands, as do most other outlets. Balax is an excellent source for technical info, specifically tap drill sizes for form taps, and their data is relevant even if you don't use their taps. Personally, I prefer OSG taps, on a cost/quality value ratio. If you treat them right, they last literally forever.

FWIW... You can also use form taps in Delrin. The screw acts like it doesn't want to go, but it will with a wrench. It acts like a NyLock nut. If you're having trouble with screws backing out of a Delrin part, due to vibration, try stepping up to the next size and using a form tap. You're welcome.

Hope this helps. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine and Precision LLC

 

[John Beardslee]

Hi Brad
Are “Roll Form” taps recommended for cast aluminum? I’ve used them for steel and aluminum extrusions as well as billet applications but never on castings.
Thanks John

 

[Brad Christy]

John,

Absolutely. I actually prefer form taps in cast aluminum, as cutting taps can sometimes catch a chip and drag it out when you back out, ripping the threads out as it comes.

I can all but guarantee the tapped holes in our engine castings were form tapped. For two reasons:

1) Formed threads are actually stronger due to work hardening, even in aluminum.
2) There is no chip to deal with. The tap can be driven right to the bottom of the hole in one shot. I've actually driven them into the bottom using a clutched tapping head; just let it hit bottom and slip the clutch.

I've used form taps in just about everything. I even used them in some pure molybdenum. I do know, though, for a fact, they do NOT work in 440 stainless, due to an utter lack of ductility. They just stop and snap. Ask me how I know..... I'd also guess they wouldn't work well in cast iron. I also have not had the sack to try them in titanium. Hell, cutting taps stick bad enough in Ti.

Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine and Precision LLC

 

[John Beardslee]

John,

Absolutely. I actually prefer form taps in cast aluminum, as cutting taps can sometimes catch a chip and drag it out when you back out, ripping the threads out as it comes.

I can all but guarantee the tapped holes in our engine castings were form tapped. For two reasons:

1) Formed threads are actually stronger due to work hardening, even in aluminum.
2) There is no chip to deal with. The tap can be driven right to the bottom of the hole in one shot. I've actually driven them into the bottom using a clutched tapping head; just let it hit bottom and slip the clutch.

I've used form taps in just about everything. I even used them in some pure molybdenum. I do know, though, for a fact, they do NOT work in 440 stainless, due to an utter lack of ductility. They just stop and snap. Ask me how I know..... I'd also guess they wouldn't work well in cast iron. I also have not had the sack to try them in titanium. Hell, cutting taps stick bad enough in Ti.

Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine and Precision LLC

Thanks, good info. I’d bet it would be good on that sticky aluminum fixture base that Terry used for his dyno/run in stand.