Securing Powermat Chainsaw Screws: Prevent Self-loosening for M5, M6 & M4 Threads in Aluminum

Hello.
I am asking for advice on securing screw threads against self-loosening.

The case concerns a Chinese petrol chainsaw with the trade name "powermat", such a tiny branch for one hand.
As a result of vibrations, all 4 M5 screws securing the motor body to the saw housing and 2 M4 screws securing the oil pump to the motor body have twisted or cut, and the holes in the aluminum body have torn or dented threads.
Today I disassembled this crap into the first parts, and it can still be saved, I will convert the M4 screws to M5 and M5 to M6.

I only combine it in such a way that instead of screws, I will screw into the aluminum body pins made of 8.8 strength allen screws, and on the other side, nuts with a plastic insert so that they do not unscrew by themselves.
However, due to the fact that the lengths of the threads in the aluminum body are about 8-11mm, the pins have to hold tightly together and cannot unscrew themselves because in a moment the effect will be as above and drilling to the next diameter is no longer an option, because it simply will not be possible "meat" and from which to drill.
The material of the motor body is quite soft some kind of aluminum alloy.
Therefore, the threaded connection of the steel pin with this aluminum body must be glued with something else, not stick together, I don't know ... secure it so that it does not unscrew.

Now the question is: what to screw it, what to use, paint, hermetic, some glue, high-temperature silicone? Please take into account that the engine body gets hot from the cylinder.

I found on the internet some wonderful American anti-loosening agent called "pro seal thread lock" but I have never used anything like this or similar preparations. Has anyone had experience with this?

Maybe such a measure: http://www.loctite.pl/zabbezpieczanie-pocze-gwintowych-6474.htm - works well in aviation ...

wzagra wrote:

Maybe such a measure: http://www.loctite.pl/zabbezpieczanie-pocze-gwintowych-6474.htm - works well in aviation ...

Interesting material, that's what I need. Only this price is half the value of the chainsaw.
Maybe something more in the range of a dozen or so gold, max PLN 50.

Well, maybe a Loctite agent would be good, but the price of 50 ml, hhhmmmm .... maybe more than the price / value of the entire saw ...
http://www.nokaut.pl/w-kategorii/ee6ddd05de69...acb57/10542/0/bjHK5Elk9Fbk6YJGBwc38tBtfHdL7VX
http://www.nokaut.pl/w-kategorii/b14e008d6bc9...qSsQe4Wq6TIWLdwKIwwaMKyFzqxRGGwT2JqmTpHe/OthY

Use Nord-Lock:

https://youtu.be/IKwWu2w1gGk
https://www.youtube.com/watch?v=cDlmbMV9ICU

the screw must fit this washer (undercut at the head). With the correct bolt, it cannot be unscrewed (during vibration, because the bolt can of course be unscrewed with a wrench).

misiek1111 wrote:

Use Nord-Lock:

https://youtu.be/IKwWu2w1gGk
https://www.youtube.com/watch?v=cDlmbMV9ICU

the bolt must fit this washer (undercut at the head). With the correct bolt, it cannot be unscrewed (during vibration, because the bolt can of course be unscrewed with a wrench).

Well, it is already within the portfolio.

Still, there is the issue of securing (immobilizing) the thread of the pin-motor body against loosening. When looking at the saw standing on the table, two screws are held vertically from the side of the table and two screws vertically from the ceiling. The plastic housing has metal sheets embedded in it under the mounting screws. It is enough for the pin to loosen in the body and it will screw out all the way with the nut and the nord-lock washer. Therefore, according to just me
secured thread plus nordc-lock guarantees a permanent connection.

What do you think about using a paste to seal car mufflers, will it be able to fix the thread effectively?

Cheaper option:
https://www.google.pl/search?q=K2+PROLOK+HIGH...x-b&gfe_rd=cr&dcr=0&ei=1my7WbWXEorY8gfdkbaICA
or
https://www.google.pl/search?q=Allbond+BEKO&i...x-b&gfe_rd=cr&dcr=0&ei=y2y7Wc7WOYrY8gfdkbaICA
set with Allegro:
https://allegro.pl/listing?string=klej%20do%2...h=base-relevance-floki-5-nga-hcp-aut-1-3-0905

I use the former for light connections.

In the morning I ran around the shops and in the automotive industry they offered me one for PLN 110 a 50 ml bottle, of course, I gave up such an expense, but in another store I got exactly what I was here: http://www.amtra.pl/katalog-produktow,709/threadlock-high- strength-red-ma262? brand = 961 for PLN 12.
Today I will make a test connection and see how it holds static.

From the free technologies, after tightening the nut, you can punch it with a punch at the point of contact with the bolt. You have to put a good punch on the nut, right next to the thread and hit it once. The edge of the nut will slightly deform. Certainly, it will not unscrew anymore, but if you want to unscrew it yourself, it will also be possible, but you will have to use a little more force. I have such marked wheels on an old lawn mower and I can say that they have not unscrewed for many years.
Greetings!

I will share my doubts, although I may be wrong. A "rethread" of 1 mm across the diameter may degrade the strength of the joint, not improve it. The thread grooves may come out in such a fragment that the vibration and the notch effect scatter it onto the undulated tube. If you plan to use nuts anyway, it might be better to make "smooth" holes and use "classics" - bolts with flat washers under the heads and nuts, and security in the form of additional screw spring washers. Let the workshop mechanics specialists have an opinion on my thinking. Krzysztof Podstawa

Mr. Krzysztof, your doubts are quite right, but there is no way to do it on the M8 because the tabs from the body in which the screws are screwed in will have a wall thickness, as I do not know what to compare, but let it be like a pen casing.
If it were possible, I would have done it.
It's just that the body is made sparingly and at the same time cheesy that you would have to see it with your own eyes, just a disposable one. The material of the body itself, in its mechanical properties, does not resemble, for example, aluminum, for example from an old motorbike engine, it is simply soft.
This repair, if it is successful, will be fine, and if the pins "come out" of the body in some time, it will only be disposal.

I was considering converting to an M7 thread, but it's all unusual. You have to buy online (in the shops I was there, they didn't have a tap, dies, bolts or nuts). Now buy it all, it will cost PLN 100 for the same crap. The new Chinese saw costs about PLN 300 (by the way, I will never buy something like this again) And for the M6 I have everything in my garage at hand, I gave it up. I'll try what will be ...
But thanks to your suggestions, I will do a test in some piece of aluminum thread conversion from M5 to M6, I will see how the thread comes out.

Buy the simplest silicone and lubricate the screw thread before screwing on the nut.

Now a friend told me to screw the pin into the body of the poxipol. Also this is some way I just have to read the flyer as with the temperature resistance of the glue.
Edit. I have already read, poxipol can withstand up to 120 degrees.

This is the glue I bought, it has a resistance of up to 150 degrees.

The cap will also go on the glue, I will additionally score it.

This is exactly what you can do. What is permanent - with glue, and what with the possibility of twisting - with silicone.

szkieletor11111 wrote:

Buy the simplest silicone and lubricate the screw thread before screwing on the nut.

The stupidest and most harmful advice.

Bambek wrote:

The cap will also go on the glue, I will additionally score it.

No scoring !!!! Even for steel with these diameters it is risky.
Anaerobic glue is enough. I have used it for repairing motorcycles many times.
Just remember to degrease the connected elements as much as possible, which will be difficult for the internal thread. Good solvent from painters + compressed air will do the job.

jack63 wrote:

szkieletor11111 wrote:

Buy the simplest silicone and lubricate the screw thread before screwing on the nut.

The stupidest and most harmful advice.

Bambek wrote:

The cap will also go on the glue, I will additionally score it.

No scoring !!!! Even for steel with these diameters it is risky.
Anaerobic glue is enough. I have used it for repairing motorbikes many times.
Just remember to degrease the connected elements as much as possible, which will be difficult for the internal thread. Good solvent from painters + compressed air will do the job.

You have the right to think so, but your colleague will do and as he sees fit.

jack63 wrote:

No scoring !!!! Even for steel with these diameters it is risky.
Anaerobic glue is enough. I have used it for repairing motorcycles many times.
Just remember to degrease the connected elements as much as possible, which will be difficult for the internal thread. Good solvent from painters + compressed air will do the job.

As for degreasing, of course I have a very good spray brake degreaser (not the one from the lidl, this one is much weaker) takes it all.
In the end, I decided that everything would go to thread glue, the nut too, and I will paint it on top.
In fact, scoring can only destroy this toy.

Thread adhesives are usually also .... anaerobic.
There are only two types. Those that only prevent rotation and those that normally stick. Since you will not unscrew the studs and the threads are already damaged and additionally cut by threading to a larger diameter (other pitches), it is better to seal them permanently. This will increase the strength of the connections.

Theoretically, the hole for the thread for the size of the M 6 screw is the minimum diameter of the hole (and at the same time the drill) should be 4.917 mm, and the maximum is 5.153, and it is practically assumed that the hole (drill) for the M 6 thread is 5 mm. So if the M 5 bolts were screwed in there, everything is correct, the threads should be fairly good (not counting, of course, how the holes for the M 5 bolts are now made). If M 5 screws were screwed in there, then just if the holes with the "old thread" are not too machined, then selecting the old thread with a 4.9 mm drill bit, for a good threading, there should be a hole for the "full thread" M 6, i.e. as above he wrote "meat only" for the M 6 thread.

The hole diameters alone are not enough. Find the pitch table M4, M5, M6 .... and compare.

Well, I do not know so much, but for example a hole (drill diameter) for the thread M 6x0.75, tolerance 6H, that is, the minimum is 5.188 mm, maximum 5.378 mm, nominal 5.2. For the thread M 6 M 6x1, the diameter of the drill is given in the range of 5 - 5.1 mm, so it is also equal to the average of the "former bolt" (where the diameter is measured on the bolt on the "outer edge of the thread) and is 5 mm, i.e. everything is within tolerance with these holes.I am a layman in these matters, but the nominal hole for the M 5 thread is 4.2 mm in diameter and after tapping with a tap, the diameter of the hole itself does not change. whether a "threaded" hole or a hole drilled for the thread, we will not insert a rod much larger than 4.2 mm into it, i.e. as much as the thread core of the M5 screw, after all this thread is on the inner edges of the drilled hole. the thread is only about the diameter of the thread on the bolt. I don't know if I am thinking right or not. If not, please give me some simple explanation.

I cannot find any relation to your argument, neither with the topic nor with what I wrote. What do you mean?
The author of the topic has to repair damaged threads with a homemade method. He planned to convert the M5 thread to M6 and probably M4 to M5.
Since the threads are in a relatively soft material, if you don't need it, it would be harmful!
Unfortunately, the pitches of the broken thread and the new thread are different and the threaded holes are "broken", so threading, despite the increase in diameter, will not provide the full height of the new thread. The outer part will be OK, but the part closer to the center of the hole will be shredded by a 1.0mm pitch thread with a 0.7 pitch thread.
Therefore, it is better to apply pins and paste them permanently.

Gentlemen, take it easy. A simple workshop method for making threads is the thread diameter times 0.8, and we have the drill diameter in mm. For M6 so 6x0.8 = 4.8 we have 4.8mm drill bit. Do not look for fits in tolerance classes and in the 3rd decimal place this is not a thread on a micrometer screw (micrometer).
For the purposes of this task, let's not open workshop guides ;)

So I dealt with this crap. And so under the M6 I grabbed what was left with a 4.8 drill and under the M5 with a 4 mm drill. The threads did not come out perfectly. After the drill you could see literally the shadow of the old jump in the hole. Here Mr. Krzysztof was right.
Recalibrating the holes with a drill was unfortunately a skill because without it, the tap was clamping after 3-4 turns.

On a school scale of 1-6, I would rate it 4+ or 5- if you prefer. Only one of the most broken ovals was the stretched 3+. At the same time, these M5s came out great and this one M6 with an oval 3+. I made the pins of hexagonal screws improved 8.8, they can be screwed in freely. I put it on the glue I mentioned in post # 8. It all twisted very stiffly, no thread let go. I gave the studs nuts with a plastic insert, a spring washer, and I also screwed them on with glue. On top, I "smeared" the cap with a hermetic and now it is cooling down.
The motor housing in the saw housing does not give off.
I am still waiting for the delivery of the oil pump because, of course, when it all started, it got a cross and (the screw), i.e. the pump drive, also hit the road by cutting a little pump gear.

PS If not everything was too easy, the rubber plug began to leak through which the fuel hose passes from the tank to the carburetor, I moved it as I unfastened the fuel hoses.
Normally k &% / # and only have attractions ...!

Ordinary nitro paint on the thread to apply and screw on - old school and proven.
And the hoses are leaking? Degrease the holes and new hoses 1mm larger. In the Chinese scythe, I have also been doing this since the application of calm. The fact that these hoses were paid for in my case and it was still terribly expensive.

Greetings.

Michał_74 wrote:

Ordinary nitro paint on the thread to apply and screw on - old school and proven.
And the hoses are leaking? Degrease the holes and new hoses 1mm larger. In the Chinese scythe, I have also been doing this since the application of calm. The fact that these hoses were paid for in my case and it was still terribly expensive.

Greetings.

It does not leak on the hoses, only around the circumference between the plug and the saw housing - the tank. To replace the cork, you need to choose one that is tighter by 1-2 mm.

As for the threads, helicoil inserts can always be provided. Of course, there are also fine threads.
As for adhesives, their holding drops significantly with the temperature. And if you have unbalanced elements that vibrate strongly, nothing will help. When they stop unscrewing, they will start to crack and so on.
So sometimes combining doesn't do much. First, give a thread insert. And you don't need ordinary paint. Because you will get nothing more.

The topic developed.
Coming back to the problem, if the new holes have been tapped with a finisher (taps are divided into: stripper, intermediate and finisher). There is not much that can be done anymore. Anaerobic adhesives will not help even the most expensive ones because the thread will be too loose. I have practiced 2 kinds in this case as has the author. 1 - screwing in screws without threading (Chinese aluminum is so soft that it threads itself from the screw (I advise against this method in places where it can break because there is little material). the threads unscrewed from vibrations there is paint but it requires drying. problems with cylinder sweating from the exhaust.
Even from the old days I remembered hermetic for engines.

And from even older times, even watchmakers used torn threads, and even without re-threading, a few hairs of linen tow are wound on the screw (even very thin) and the varnish is screwed in - it can withstand a lot of vibrations and vibrations. I have a dozen or so M4 - M6 bolts screwed into the aluminum body in the lathe (more carbon and sand than aluminum), and it has been holding the entire gear and covers for over 25 years - and the vibrations are very high there.
And the combination of hermetic and tow is a total cosmos To unscrew it, you need to heat the screw to over 450 ° C. The varnish softens and releases at over 200 ° C

Hello.
As for the tow. I used to have a SAM tractor, a Dzik 21 gearbox, a self-made frame and a 600cc Maluch engine. I broke the spark plug threads in the head and because I did not want to repair, I screwed in the candles from the FSO 1500 on the tow. The fact is different heat and all the rest of the other, including thread length, but kept over 4 years of garden work.
So good nature won over our technique.