Motor Thread Repair - Suggestions?

avictor · Oct 2, 2017

Here it is. Let's here your stories on how you fixed this. JB Weld?

PS I know the EASY answer would be replace...not going to happen. So have some fun with it!

Thanks!

George2615 · Oct 2, 2017

Not sure what that tapped hole needs to support but if it was mine I'd take it to a reputable welding shop and have them make and weld a new piece on the bottom including filling the hole with weld then drill and re-tap the threads.
If that has to support something JB Weld won't hold very long.

powerscol · Oct 2, 2017

How much metal is beyond the bottom of the hole? Can you drill deeper and tap a new thread and just use a longer bolt? Concern is the shearing action that busted this in the first place.

avictor · Oct 2, 2017

powerscol said:
How much metal is beyond the bottom of the hole? Can you drill deeper and tap a new thread and just use a longer bolt? Concern is the shearing action that busted this in the first place.

I don't believe I would be able to drill in any further, may compromise transmission. I suspect the shearing was a result of improper installation of aftermarket part (they didn't use all of the mounting positions).

avictor · Oct 2, 2017

George2615 said:
Not sure what that tapped hole needs to support but if it was mine I'd take it to a reputable welding shop and have them make and weld a new piece on the bottom including filling the hole with weld then drill and re-tap the threads.
If that has to support something JB Weld won't hold very long.

My brain tells me JB is a pipe dream. If only a cold weld had that kind of strength.
I don't like your answer with regards to welding (although its most likely the right one, lol).

flyerdan · Oct 2, 2017

It looks like there is a broken part of a bolt still in the hole, and from the vast rust area vs. the shiny parts, it has been hanging on by a thread for quite a while. If you still have the other section, the quickest and easiest fix would be to braze it back together, punch it out for the correct (or closest possible) helicoil insert. And get the broken stub out now while it's more accessible, if that is what I'm seeing at the base of the threads.

Egon · Oct 2, 2017

avictor said:
My brain tells me JB is a pipe dream. If only a cold weld had that kind of strength.
I don't like your answer with regards to welding (although its most likely the right one, lol).

George may be on the right track.
JB weld will be a waste of time.

Phillip w · Oct 2, 2017

Well here is my 2 cents worth. It looks as if there is a busted bolt or something. I would drill and easy-out that first. Do you have the missing piece? If so you can braise it as suggested or weld it. If welding with a stick welder, you going to need. Nickel rod. It welding with a wire welder use stainless wire. It you dont have missing piece, I would fill with weld using a wire welder and stainless wire. Just make little passes an keep touching up with an angle grinder as you go. Drill and tap with a carbide bit.

avictor · Oct 3, 2017

flyerdan said:
It looks like there is a broken part of a bolt still in the hole, and from the vast rust area vs. the shiny parts, it has been hanging on by a thread for quite a while. If you still have the other section, the quickest and easiest fix would be to braze it back together, punch it out for the correct (or closest possible) helicoil insert. And get the broken stub out now while it's more accessible, if that is what I'm seeing at the base of the threads.

That's an older picture. I've already extracted the snapped bolt.

Thanks for the tips!

powerscol · Oct 3, 2017

avictor said:
That's an older picture. I've already extracted the snapped bolt.

Thanks for the tips!

How deep are the undamaged threads. Depending on the grade of bolt there may be enough left to hold.

pmsmechanic · Oct 3, 2017

This looks like fun! But you aren't giving us a whole lot of information. How about a larger more overall picture with a good description of what you want to accomplish.

If you are mounting a plate and there are other holes in the vicinity then I would just drill this one all the way through and install a longer bolt. Even if you need to install a nut inside the housing to help hold.... But before I say for sure I need more information.

stuckmotor · Oct 4, 2017

Where's Shieldarc's comment? I hope he's not sick.

dragoneggs · Oct 4, 2017

I confess I am a more than just a fan of adhesive bonding, but this doesn't at first glance, look like a proper application. Could use more info... what is it? Bolt diameter/length? Female threads remaining after tap? Operating shear/tension/moment loads, torque requirements? That said, even if you have the broken off piece, my guess is you won't get a good fit up/alignment to tap threads. This appears to me, a total weld build up job by somebody that has done it before if this is somewhat important to you.

LD1 · Oct 4, 2017

I agree that we need a more overall picture. And just what is mounting there.

Perhaps with some steel, and some other unused locations on the tractor.....you can forget that hole and reinforce with some steel to other locations to support whatever was hanging on there?

JPRambo · Oct 4, 2017

In post *4 he talks about a transmission.

avictor · Oct 4, 2017

powerscol said:
How deep are the undamaged threads. Depending on the grade of bolt there may be enough left to hold.

The undamaged threads are about 1" deep. I'm using an 8.8 M12-1.75 bolt. For the broken bolts, I would say it probably catches the first 4-6 threads.
I may just use it as it. The previous owner didn't utilize two other mounting bolts located perpendicular to these bolts (which would support any downward force on the broken bolts). Now that I have those mounted, it's quite solid.