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Helicoil help needed

NedHan79

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8 Nov 2018
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1,096
Started to build the front of the car back up and in the process I have stripped a few threads. One being the top caliper bolt on the drivers side and the others are 2 of the front anti roll bar bolts into the subframe. I know the hub is a known one for stripped threads and I'm guessing the alloy subframe is just the same.

I have some tap and dies there which I've used on basic jobs but I've never used helicoils. Is it simply drill out to a lager hole, tap it for the larger helicoil and screw it in?
Also, does anyone have any idea what size of items I need to buy? I think they are both m12 but tbh I didn't really look.

As usual all help very welcome
 
Hi Ned,

Yeah that's pretty much it.
Larger drill to drill out old hole then a helicoil is like a stiffly wound spring of metal that forms the new thread. There's a tang in the bottom you use to wind it into the new hole once the hole is tapped with the correct helicoil tap. Once the insert is wound down to the required depth you use a small punch to break the tang off the bottom so your bolt won't bottom out on it.

A helicoil kit will usually include some inserts, the tap, insert tool and sometimes the drill.




You also have timeserts which are solid tubes of metal featuring the correct original thread on the ID (internal diameter) and a larger thread on the OD (outer diameter).

Martin covered these along with another of his excellent 'how to" videos a little while back.

Timeserts are stronger but helicoils are fine when used properly. Some parts we produce at work ask for helicoils from day one. Mainly Ali parts where the threads won't stand up to repeated use.

Biggest thing to get right is the angle of your drill for the insert. Go in incorrectly, even a few degrees and whatever you then bolt upto the helicoiled part will not sit flush. Not so bad on static things (although not ideal obviously) but do it with your hub/upright and every time you brake your caliper will flex.
My mate Craig on here had an annoying creak when braking hard in his C2. Some bozo had done exactly that.
He had to source a new hub carrier. :nooo:

PS I can't help with bolt sizes off the top of my head. I'm lucky in that I can take them into work and use the female thread gauges to tell me what it is.

You can measure the width obviously but the pitch is harder as there isn't much difference between 1.5 and 1.75 etc. :wink:
It's still totally doable with a vernier though.

Good luck. :thumb:
 
Caliper bolts are M12 x1.5 pitch.

Yes you just drill and tap a larger diameter hole then screw the helicoil in with the insertion tool and when it gets to the bottom of the hole the tang at the end that you screw it in with snaps off :thumb:
 
Sounds good guys. Thanks. The only thing I need to figure out now is the size of the thread :?:
 
Get on youtube, plenty of stuff on there.... :thumbs:
 
Helicoils are often too short, make sure that you get them the correct length for what you need.
 
I've done a few helicoils in my time. Make sure you get a kit that comes with the correctly oversized drill bits. Also, by far the most vital aspect of a successful helicoil is accurately drilling out the hole. Use a drill press/pillar drill and secure the part on the bed properly and accurately, or if on the car, make a drill guide from whatever scrap you have available. The tapping of the hole and inserting the coil are the easy parts.
 
Ordered a kit on eBay this morning so I'll see how I get on.

Thanks for the heads up
 
I wouldn't be too keen on helicoils holding my calipers on.
 
For anyone that needs to know, the front arb bolts are m10x1.5.
 

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