Thread repair

[Bentwings]

Timo, I like the picture of the double-ended stud in your post. When the threads look good under magnification, with no tearing or irregular crests, it is a satisfying sight.

One thing I forgot to mention about helicoils is that it is very important to tap the hole deep enough with the special helicoil tap. If not, the helicoil will taper in at the bottom and the bolt will lock up in it and then you have a mess on top of a mess.

Edit: And I also forgot to mention that the special spring loaded tool (like a spring center punch) for breaking off the helicoil insertion tang after it is installed, is called a tang-banger.
Yup, that's the proper technical name.

thanks for the tip. When searching for these I saw different numbers so I assumed it was the depth theyvwerevtonbebinstalled at . I’ve just made sure I tapped deep enough that the part was in full depth according to its size . I surely can see that tapping too shallow will cause problems or as you noted the depth of tapping the set of inserts I have are all about he same ratio of diameter to length so you tap for hem

Byron

 

[L98fiero]

Is it possible to install a3mm heli coil in a 4 mm threaded hole . Will the new 3 mm screw hold reasonably well?
Byron

No, the major diameter of an M3x0.5 STI tap is 3.719mm diameter.

 

[timo_gross]

No, the major diameter of an M3x0.5 STI tap is 3.719mm diameter.

M3x0.5 should have a major diameter of 3 mm +- something. Plus 0.7 mm oversize seems a lot.

 

[L98fiero]

M3x0.5 should have a major diameter of 3 mm +- something. Plus 0.7 mm oversize seems a lot.

I listed the major diameter of the tap, the tap drill size, direct from Heli-coil, is 3.15mm for Aluminum and 3.2 for steel, magnesium and plastic though other tap manufacturers just go with 3.15mm. The way Heli-coil groups aluminum separate and steel in with magnesium and plastic seems a bit odd but they probably have more experience with Heli-coils than I do.

 

[elcid]

JB weld is temp fix and will fail down the line.

Dave

One of my sons decided to mash the fallen apples with our large flymo XL500 grass cutter and stripped the keyway, the two options were try and weld it and then cut a new keyway, or buy a new engine crankshaft, one I would have to pay for the weld and the other nearly half the price of new engine.
Looking about for another solution I came across a website that suggested JB weld, they had repaired a crack in a cylinder head, used it to repair stripped bolt holes and another repaired a power takeoff shaft keyway 9 years earlier.
So I gave it a try, that was back in 2008 and the mower is still running and still hits the odd rock or stone, I do keep away from the fallen apples though.

 

[mcostello]

One of my sons decided to mash the fallen apples with our large flymo XL500 grass cutter and stripped the keyway, the two options were try and weld it and then cut a new keyway, or buy a new engine crankshaft, one I would have to pay for the weld and the other nearly half the price of new engine.
Looking about for another solution I came across a website that suggested JB weld, they had repaired a crack in a cylinder head, used it to repair stripped bolt holes and another repaired a power takeoff shaft keyway 9 years earlier.
So I gave it a try, that was back in 2008 and the mower is still running and still hits the odd rock or stone, I do keep away from the fallen apples though.

Maybe those apples are to be used to make hard cider, they are harder You know.

 

[elcid]

My Yamaha Diversion's front wheel needed new discs, the first bolt came out easy enough but the next one broke, then the next, steel bolts in aluminium just love each other so much they don't want to part, so off to a local engineering works that deals with North Sea oil rigs and for £200 they removed all the bolts and put in Tappex stainless steel inserts.

 

[Bentwings]

M3x0.5 should have a major diameter of 3 mm +- something. Plus 0.7 mm oversize seems a lot.

I’ve got a tap drill for m3 and m4 . I forget what number drill is closest I have th stop . I’ll have to check the heli coil tool is shipped so I YHINK it best to just wait until it gets here Tuesday or Wednesday. I think I’ll drill the new hole slightly off center or slight angle so the threads clear the hub better I’ve got 3 different flywheels each have different hub sizes I had planed on making these all the same . There is not a lot of difference I have couplers so I can couple the engines together either with the long hub flywheel od the shorter ones . The eccentrics have the same hub diameters so once I get the heli coil tools I’ll be able to use them if I had seen this issue I could have relieved the crankshafts enough to use the set screws without a problem . I guess it’s a learning process . If our lathe gets fixed I’ll come up with a powered spindle mounted on a quick change tool holder. I can then use the dremel saws as cut off tools they will get a much stronger arbor they will work on dog metal like aluminum and brass

I’d realy like to make the lathe spindle capable of indexing but I just have not got that far yet there has been some that have done this so standard index plates can be used . It takes a bit of work but gives some versatility to the lathe

Byron

 

[Bentwings]

I’ve got a tap drill for m3 and m4 . I forget what number drill is closest I have th stop . I’ll have to check the heli coil tool is shipped so I YHINK it best to just wait until it gets here Tuesday or Wednesday. I think I’ll drill the new hole slightly off center or slight angle so the threads clear the hub better I’ve got 3 different flywheels each have different hub sizes I had planed on making these all the same . There is not a lot of difference I have couplers so I can couple the engines together either with the long hub flywheel od the shorter ones . The eccentrics have the same hub diameters so once I get the heli coil tools I’ll be able to use them if I had seen this issue I could have relieved the crankshafts enough to use the set screws without a problem . I guess it’s a learning process . If our lathe gets fixed I’ll come up with a powered spindle mounted on a quick change tool holder. I can then use the dremel saws as cut off tools they will get a much stronger arbor they will work on dog metal like aluminum and brass

I’d realy like to make the lathe spindle capable of indexing but I just have not got that far yet there has been some that have done this so standard index plates can be used . It takes a bit of work but gives some versatility to the lathe

Byron

very good point if it is not all the way the bolt or screw could stick and back the coil out just when you need it to stay put.

 

[Bentwings]

very good point if it is not all the way the bolt or screw could stick and back the coil out just when you need it to stay put.

I have some 3mm double ended studs similar to the picture. The un threaded part I just a tiny bit larger than the minor diameter ofvthe threads it’s just enough to clear the hub in the counter bore. In the center of the collar. The issue I’d now the c’bore that is in the collar for the 3mm socket head screw. I E it’s too deep so it also interferes. I did bevel the bottom of a screw but then it doesn’t have much of a flat to bear on in retrospect if I could have sat down and designed the proper means of securing parts all of this could have been avoided. But…. Oh no. Smart me was going to make do with purchased parts that had incomplete information
Now I have to “ force” make shift stuff work . I know better than this so y’all can let fly with “ I told you so s” and any uncomplimentary things even “ mud throwing “ I Deserve it . Thanks for all the help an suggest ions.
I have to tell a story from the auto shop years ago we had a very good mechanic working part time he was a real wrench turner and could fix about anything he had a chev on ton crew cab that had bad u joints. So one night after hours he pulled it in to fix it . We all went home thinking it would be done and gone the next morning . “ however in the morning it was still there curious we went behind the shop wall and found the big steel drive shaft beat absolutely flat end to end with a slight arch like a banana apparently he could not get Eva joints out or the new ones didn’t fit throwing a fit he had totally flattened the drive shaft these are big and long on one ton diesel trucks this mess was laying on the floor among a couple sledge hammers and a lot of dust . It was so funny we just roared . Later in the day a brand new complete drive shaft arrived from a local mfg. all nicely pained black ready to install . That evening the guy came in and didn’t say a word just installed the new drive shaft then went home . 30 yrs later this is still a favorite “ remember the time when…” story .

 

[timo_gross]

...... Now I have to “ force” make shift stuff work. ....

A major moral difference is, whether you have to deal with your own false economy (time included) or (while getting even more grumpy about it) dealing with someone elses false enconomy .
Patience, learning and humor keeps us going. Better learned the hard way, than to remain stupid?

Once my colleague said: "I could have told you!" I answered: "Why did you not tell me, when I asked!"
Lesson learned: No "could haves" anymore.

I fix my flywheels with superglue and do not even bother to degrease the parts. So far it was never a problem.
You can guess how powerful my toys must be.

Greetings Timo

 

[Bentwings]

A major moral difference is, whether you have to deal with your own false economy (time included) or (while getting even more grumpy about it) dealing with someone elses false enconomy .
Patience, learning and humor keeps us going. Better learned the hard way, than to remain stupid?

Once my colleague said: "I could have told you!" I answered: "Why did you not tell me, when I asked!"
Lesson learned: No "could haves" anymore.

I fix my flywheels with superglue and do not even bother to degrease the parts. So far it was never a problem.
You can guess how powerful my toys must be.

Greetings Timo

thanks for your reply I love it .
I thought about either lock tite or super glue for fly wheels when I have the final assembly operating I’ll do one or the ther . Since the flywheels a brass just heating them a little should break the bonds if necessary . I have a shaft extension made from 6mm bar plus 6mm I’d capillary tube it’s 7 mm od so I can make either diameter go through the flywheel by just opening the bore . The capillary tubes are very close tolerance so it fits over the shave very well it too could b super glued or loc *** assembled .
I just saw a note that the heli coil tool has been delivered to my mail box up the street so I’ll walk up and get it .

Byron

 

[Bentwings]

thanks for your reply I love it .
I thought about either lock tite or super glue for fly wheels when I have the final assembly operating I’ll do one or the ther . Since the flywheels a brass just heating them a little should break the bonds if necessary . I have a shaft extension made from 6mm bar plus 6mm I’d capillary tube it’s 7 mm od so I can make either diameter go through the flywheel by just opening the bore . The capillary tubes are very close tolerance so it fits over the shave very well it too could b super glued or loc *** assembled .
I just saw a note that the heli coil tool has been delivered to my mail box up the street so I’ll walk up and get it .

Byron

I just picked up he heli coil tool. It’s 86 deg f so I need to cool off after my walk.
It looks fine in the package . Tap drill tap and insertion tool along with a few heli coils. I’ll try it out later

 

[Bentwings]

Ahhh yes, the voice of experience. Much of the success of a project depends on our ability to remedy a mistake gracefully.
Lloyd

I finally received the installation tool along with a few more inserts .

So I carefully ran the heli oil tap in the existing hole it cut easily . Then I used the tool to install the coil. The taped threads are definitely under size as noted . After I got the coil installed I looked at the project under big magnifying glass . The new screw goes in just fine know it won’t withstand heavy “ cranking down” so I can squeeze the collar in the vice to Bend it slightly . I used the dremel saw to cut the bend slot a bit deeper so the effect is the collar works fine , it’s just makeshift, I know this and I’ll operate it as needed The ultimate cure is a correctly made unit . However our lathe is still down so I’m looking into a redesign of the whole part so the clamp is built in I’m working on re learning my solid works . It’s a bit slow but it does follow my previous knowledge . I had to get exfinity -Comcast out to get my lap top computer hooked up so I can use the bigger tv screen so I can see what I’m doing It meant moving a bit of furniture around but I now have a screen I can more or less see and read . The goal is to create a model that can be 3 s printed I can use the correct screws and I have heli oils that could be installed if necessary . I’m taking a chance but I may be able to make a test run to get correct timing set up a