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Discussion Starter #1
I have a threaded screw boss that is broken on a small engine. I guess the metal is cast aluminum. Should I use J-B Weld product called Steel-Stik for the repair? It is a mold able epoxy that can be drilled and tapped. I have not use this product before. Will it hold if cleaned properly?
Any suggestions?
Thanks

Merry Christmas
 

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It's worth a shot. Looks like a very small 2 stroke engine. Those cases can be very difficult at best to weld due to it being cast aluminum. If your JB Weld doesn't work, you may have to get a new case half if it's even available.

What are we working on?
 

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How much pressure is on the screw/boss? In other words what’s it holding?
 

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My knee jerk thought by looking at the damage and assuming its of value to you is to jb the piece and helicoil it to preserve the threads .
 

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Use the JB Weld. Then if possible, put a small hose clamp around the post to strengthen it.
 

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Use the JB Weld. Then if possible, put a small hose clamp around the post to strengthen it.
Or wrap a steel wire around it several times a smear with more JBW.
 

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Discussion Starter #9
Wow, you folks are the best.
Yes, this is a two cycle engine from a McCulloch Mini-Mac 25 chain saw.
I know this is not a tractor, but I also think a lot of you guys wrench on other machinery. :lol:

That broken tapped boss is one of the three locations on the engine that holds the engine to the outside casing. This location is the very bottom of the saw.
I don't know if the saw was dropped and caused this to happen. Casing is fine. Or if someone was over zealous in the tightening of the screw. I do not believe it has to hold a lot of pressure.
Option 1 Clean and replace broken section along with filling tapped cavity and re tapping for screw.
Or
Option 2 Leave small broken piece aside, do not use. Fill tapped cavity and build a new side wall for screw, using the epoxy, and then re tap.

Note to self. Make sure I have a bottom tap.

Regards
 

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Clean it VERY GOOD

Cast aluminum is notorious for oils seeping into the pores of the metal, a way I use to clean it is take a propane torch and heat the bolt boss just until you see the oil start to come from the metal ( doesn't have to get extremely hot) and clean it quickly with a NON-FLAMMABLE cleaner the best that you can- you can never get it all. This will help the epoxy stick better, and when you put the epoxy on make sure not to leave any cavities in it completely fill it - don't try to save the current hole. Then drill and tap the new hole. The idea of putting a clamp or thick steel wire around it is good also to give it more strength. I have made a lot of repairs this way and had very good success. I hope this helps and good luck with your repair.
 

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Wow, you folks are the best.
Yes, this is a two cycle engine from a McCulloch Mini-Mac 25 chain saw.
I know this is not a tractor, but I also think a lot of you guys wrench on other machinery. :lol:

That broken tapped boss is one of the three locations on the engine that holds the engine to the outside casing. This location is the very bottom of the saw.
I don't know if the saw was dropped and caused this to happen. Casing is fine. Or if someone was over zealous in the tightening of the screw. I do not believe it has to hold a lot of pressure.
Option 1 Clean and replace broken section along with filling tapped cavity and re tapping for screw.
Or
Option 2 Leave small broken piece aside, do not use. Fill tapped cavity and build a new side wall for screw, using the epoxy, and then re tap.

Note to self. Make sure I have a bottom tap.

Regards

Apparently we break a lot things as well. Perhaps the thing I like with the forum the most is seeing I am not the only one who breaks things that are not easily replaceable and am not the only one that finds things broken that I don’t remember breaking.:laugh:

I like the hose clamp idea, I really have never really thought of the wire wrap idea but that is a good one. It is also possible you could build a bridge from the other boss that is there if nothing in the way.
 

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Apparently we break a lot things as well. Perhaps the thing I like with the forum the most is seeing I am not the only one who breaks things that are not easily replaceable and am not the only one that finds things broken that I don’t remember breaking.:laugh:

I like the hose clamp idea, I really have never really thought of the wire wrap idea but that is a good one. It is also possible you could build a bridge from the other boss that is there if nothing in the way.
It is not always things you forgot you broke but when something comes back broken when borrowed and you did not know until you go to use next time.:banghead::nunu:
 

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It is not always things you forgot you broke but when something comes back broken when borrowed and you did not know until you go to use next time.:banghead::nunu:
Another option is to epoxy in a threaded stud. Then use a nut/washer. Less chance of stripping a threaded epoxy hole.
 

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Another option is to epoxy in a threaded stud. Then use a nut/washer. Less chance of stripping a threaded epoxy hole.
This to me is your best option. I'd also consider making a sleeve out of some sort of tubing to put around the boss and then filling the gap with some sort of high temp epoxy.

Or you could try a variation of this with placing a threaded stud in the cleaned out remainder of the boss and if you have a MIG or TIG welder, you could build up a cover over the stud. As others have said, cast aluminum is tough to weld from what I've seen Jody of Welding Tips & Tricks on YouBoob has said on the subject. I'd still put a sleeve, hose clamp, or wire wrap around it.

Or if the boss is only securing a decorative cover, could you leave the cover off?
 

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Wow, you folks are the best.
Yes, this is a two cycle engine from a McCulloch Mini-Mac 25 chain saw...

That broken tapped boss is one of the three locations on the engine that holds the engine to the outside casing. This location is the very bottom of the saw....
... I do not believe it has to hold a lot of pressure.
Spend a moment thinking through the forces the saw encounters and how they are transferred to the user's hands. Then ask yourself if this bolt has anything to do with the transfer of those forces. If it's not involved, then ask what might happen if your repair breaks. Are there parts that could fly up and hit the user of the saw. If the bolt doesn't transfer force to your hands and it doesn't secure parts that might hit you if it fails then you are safe to repair in whatever way works. Otherwise you will want to get a new saw or repair it in a way that is as good or better than the original.
My physicist wife is always reminding me "Consider the forces your tool creates and how they are transferred into the ground. If you are part of that transfer, then be careful!"
 

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Heat?

Heat may be an issue with JB Weld. Most epoxy compounds are not very heat resistant. It's still worth a shot but if that area is subject o high temps, I wouldn't be surprised if the JB let go.

Treefarmer
 

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Spend a moment thinking through the forces the saw encounters and how they are transferred to the user's hands. Then ask yourself if this bolt has anything to do with the transfer of those forces. If it's not involved, then ask what might happen if your repair breaks. Are there parts that could fly up and hit the user of the saw. If the bolt doesn't transfer force to your hands and it doesn't secure parts that might hit you if it fails then you are safe to repair in whatever way works. Otherwise you will want to get a new saw or repair it in a way that is as good or better than the original.
My physicist wife is always reminding me "Consider the forces your tool creates and how they are transferred into the ground. If you are part of that transfer, then be careful!"
Get a steel pipe of the appropriate size, cut to length then fill up the whole thing with JBW. Seems to me if you do that and the stud idea, would be much better than new.

Sent from my SM-N910V using Tapatalk
 

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