Road Wheel Thread Repair with Heli-Coils

Big_John

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A couple of my Road Wheel centers have stripped threads. You can usually give the center a turn and use some alternate holes, but some ham fisted tire changer in the car's past made sure that wasn't going to happen. So... A repair was needed.

Typical stripped hole.

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First, you'll need a Heli-Coil kit. The threads are 1/4-20.
https://smile.amazon.com/gp/product/B0002SRE8Q/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

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Included in the kit is the special Heli-Coil tap, an inserting tool and 12 heli-coils.

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You'll need some drills, tap wrench, small punch, small hammer, and an electric drill. A countersink bit, like shown is nice but not a must.

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I used my trusty Craftsman hand drill. Having a variable speed and easy reversibility is handy.

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The proper size tap drill is a 17/64".

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Because of the type of material, I first used a 15/64", then a 1/4" and then finished with the 17/64". The material that they cast the wheel centers from will tend to grab the drill so you want to "sneak up" on it to get the hole drilled to size.
 
You'll want to mark the drill with some masking tape so you don't drill too deep.

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Finished drilled hole. A countersink bit was used to put a slight chamfer on the hole.

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Next comes tapping the hole. I use this Do-All brand wax meant for cutting tools, but you can use about anything as a cutting oil.

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Tapped hole. Keep the tap as straight as possible and twist it about a half turn in, then a half turn out to break the chip as you tap the hole. If you don't do that, you're taking the chance of ruining the threads or even breaking the tap.

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Now to inserting the Heli-Coil.

The Heli-Coil has a little drive tang on one end.

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The Heli-Coil is threaded on to the inserting tool until it engages the tang.

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Twisted into the tapped hole until it is just past flush and the insert tool is twisted back out.

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When you look in the hole, you'll see the tab.

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Put the pin punch in the hole and with a quick, sharp rap with the hammer, break off the tab.

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Finished holes. When you are all done, the Heli-Coil repaired hole will be stronger than the original hole.

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Last edited:
Thank You! Nicely done, and very informative! (You almost have me convinced that I might be able to do it!)
:lol:
 
I'm very much diggin' that well-seasoned brass hammer!

Circa 1953 or so, perhaps?
I worked in a machine shop part time when I was in high school and they made them for a customer. Let's say it was a parting gift. So... circa 1972.
 
:thankyou:

It's great that there's enough meat on the posts to drill oversize for the helicoil.

That machine shop size tube of Do-All looks like it's been around for a while, and will be around for a long time to come.

Jeff
 
You split it up short and sweet with good pictures...even a simpleton such as myself could follow your directions. Thanks for taking the time to share.
 
Great job by you on the repair and explanation on how to do it. As with any machine work, patience is the key. Thanks for sharing your experience.
 
HeliCoils work! I used HeliCoils to repair a friends Mahindra tractor that had broken in half. Tractor is still working 5 years later.
 
Thank you @Big_John , funny thing, it never even occurs to me... most of the time, that folks are unfamiliar with repairs like this.
 
Thanks for posting this @Big_John ! :thumbsup:
I've got a couple caps with threads needing repair on my center caps. This definitely looks like a better way to go than trying to tap that old pot metal.
 
Now to inserting the Heli-Coil.

The Heli-Coil has a little drive tang on one end.

View attachment 269052

The Heli-Coil is threaded on to the inserting tool until it engages the tang.

View attachment 269053
View attachment 269054

Twisted into the tapped hole until it is just past flush and the insert tool is twisted back out.

View attachment 269055
View attachment 269056

When you look in the hole, you'll see the tab.

View attachment 269057

Put the pin punch in the hole and with a quick, sharp rap with the hammer, break off the tab.

View attachment 269058

Finished holes. When you are all done, the Heli-Coil repaired hole will be stronger than the original hole.

View attachment 269059

Terrific, John. I always wanted to know how a heli-coil repair is done. I think I'll give it a go, next time I'm in a jam with stripped out threads.
 
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