HOW TO FIX A STRIPPED OUT THREADED INSERT

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Sandblaster
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HOW TO FIX A STRIPPED OUT THREADED INSERT

Post by Sandblaster » Sun Oct 21, 2012 7:57 pm

HOW TO FIX A STRIPPED OUT THREADED INSERT.
While working on my K5SM (KX500 Supermoto) project I ran into a problem with a threaded insert that holds the sub frame onto the main frame.
The previous owner had stripped the threaded insert that is welded to the frame and he used a Heli-Coil to fix it without drilling it out and using a Heli-Coil of the correct size.
Here is the threaded insert that is stripped:

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I could get the correct nut size, grind the old nut off and weld a new nut on.
Since the frame is powder coated I wanted to save the powder coating.
To the right is the Heli-Coil that was used to fix the problem.
To the left was the EZ-Lok I was going to use to fix the problem.
Unfortunately the EZ-Lok was too large and I would ruin the threaded insert if I tried to use:

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For him I'm sure that the Heli-Coil was fine as he just wanted to ride the bike and didn't care what size bolt it took to get him going again.
However, I could not use the stock bolt with the Heli-Coil and I want to use the stock bolt:

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So, I decided to fix the problem by welding up the the threaded insert and then drilling it and tapping it to the correct size.
In this case it is M8 x 1.25.
Knowing that the weld material is by far harder then the insert material I decided to give myself a small advantage by making a small plug from a bolt and welding that to the bottom of the hole.
Doing this allows me to get a pilot hole started easier in the softer material of the plug.
I took a small fastener and ground the edges off the head so the the head fit into the stripped out insert:

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Once I verified that the plug fit into the threaded insert I cut off the threaded part of the plug so that I was left with a stripped out head.

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Next I held the plug into the end of the threaded insert that I was going to drill and tap into.
Again, I wanted softer material to drill into to begin with.

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If bikes are for kids I'll never grow up.

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Sandblaster
Posts: 6312
Joined: Thu Jun 07, 2012 3:50 pm
Location: Eugene, OR
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Re: HOW TO FIX A STRIPPED OUT THREADED INSERT

Post by Sandblaster » Sun Oct 21, 2012 8:10 pm

Before welding the plug in I drilled out the stripped threads to have a nice clean weld surface.
Once I had the plug held firmly in place I welded the entire hole up.
Next. I used a small hand grinder to clean up the weld so that I had a nice flat surface for the drill to get a purchase point on.
Once that was done I used a punch to get a nice centered point for my drill to get started into.
Using a 1/8" drill it I started the pilot hole.
Drilling into the soft material of the plug is easy.
Drilling into the weld required a good quality drill bit, slow speed, with something to keep the drill bit cool.
WD-40 is what I had on hand so that is what I used as a coolant.

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Now I have a nice small pilot hole to help guide a larger bit:

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Next I drilled out the pilot hole with the correct size bit.
In this case I need to tap to M8 x 1.25 which requires a 6.9mm or 0.272" drill bit.

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Since I destroyed my tap on the last project I did, I will need to get another to finish this article.
Stay tuned :D
If bikes are for kids I'll never grow up.

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Sandblaster
Posts: 6312
Joined: Thu Jun 07, 2012 3:50 pm
Location: Eugene, OR
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Re: HOW TO FIX A STRIPPED OUT THREADED INSERT

Post by Sandblaster » Fri Oct 26, 2012 10:28 pm

A little tapping work...

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Done!
The bolt fits perfectly and I couldn't be happier:

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Any questions or suggestions?
Feel free to email or post.
Thanks!
SB
If bikes are for kids I'll never grow up.

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