heli coil or nut insert?

i have a threaded tapped hole for my shock mount on my dh team, shall i helicoil it or drill it out and use a nut insert..? i can't use a bolt/nyloc as my linkage won allow it..any ideas?

Helicoil every time if one will go in, Its the strongest minimal material removed to make it fit, strong thread Dunno what yo mean by a nut insert.

Sorry TJ, avoid helicoil if at all possible, it's just a peice of wire wound into a spiral, and isn't all that strong. For maximun strength, and minium OD you are right to use a "nut insert". Find a local garage/engineering shop who can fit a Wurth Timesert (below). Dont use keyserts etc with the hammer in pins, the od is too large, and you'll have to remove too much material to fit.

Helicoil not strong? Aren't they used to replace striped spark plug threads?
Using an insert means drilling out a larger hole which may result in an overall weaker solution if the hole is close to the edge of the material. If this is ok insert will be better but helicoil should be ok.

Helicoils are used because they are fast, easy, and cheap. They are not a permanent repair. One day, when you least want it to happen, the end of the wire on the helicoil will pick up on whatever you are trying to screw in to it and wind itself right out of that hole, and you get to start over. Take a look at the picture of the timesert, its no larger in OD than the helicoil, but the threads are timed (hence the name) to overlap, and form a sleeve, way stronger.
Timeserts are used on sparkplug threads, and anything else you care to name, especially if you are threading into ally or mag, and not just as a repair, but fitted from new. There are a couple more steps involved to fitting them, but the only tools required are a drill and a tap wrench (just like a helicoil). The kits and inserts are DEAR, so for a one off, sub it out.

Wurth part numbers:

http://www.wurth.co.uk/catalogue/pdfs/UK-CD_04_6019.pdf

Nut inserts can really only be used on thin materials as they are used similar to a pop rivet. You drill a hole then fit the nut insert that uve screwed onto the pliers. Pull the pliers tight so you compress the insert. It squashes a bit and grips the thin material. Its really a sheet metal fastener.

I would use a helicoil all the time. Been using them for years to mount brake calipers to aluminium uprights in GT cars. The likes of AP and Brembo dont class them a temporarily……

Given that the tread of a helicoil isn't really going to be taking any load on a shock mount, I'd say it's going to be fine. Unless you're taking your shock off twice a day, I don't see there being any real worry about it coming out. It will be stronger than the original thread in the parent material if that was ally.

I've used them to save Mani-poo post mounts before and it's still going strong. You need to think about that the bolt was actually doing to decide if such repairs would be okay.

Timesert:

Not to be confused with a Rivnut:

chopper – I think you are wrong about helicoils. Some race engine builders put them into brand new engines in places where bolts are going to be removed often.

I have some helicoiled threads on my motorbike. Never any trouble even in cylinder head bolts. They are far stronger than the original alloy thread

The insets you mention are a good solution maybe even the best but do require more metal to be removed

thanks for all your answers, food for thought there.

i was simply looking for something like a rivnut but without the squeezing property (like a chain ring nut insert). ie i just want to screw into it without it gripping anything.

i'll look into the timesert thingy, if i can't find anyone then it'll be a helicoil from my local engineering firm,

boo all i wanted to do was fit one and get it done…

just found a local motorbike shop advertising wurth timesert repairs, will go give them a shout tomorrow.

thanks all for your help.

FMH

can't do wurth timeserts due to not enough depth of material, apparently need around 11mm whereas i have 8mm, gonna do the tour of local engineering firms this morning in the rain looking for someone to sort it out….

same4 thing happened to a mates DH team out in france, we found a thin nut and filed the frame (linkage iirc, could be wronng) for clearance to bodge it for the rest of ythe holiday.
I'd go with nut insert over helicoil if it's the same bit on your frame

GW its both shock mount on frame and linkage holes threaded, (not me that did it it was a mate with big pudgy farmers hands!!)

just got back from local engineering firm, very nice chaps and the guy is an mtber, cant find nut insert that would suit so is going to helicoil and see how we go. i guess if it screws up (sorry couldn't resist!) then just fill in with weld and re tap.

gutted about the inserts though, local fastener company didnt come up with anything just the rivnut type which wont suit, may dremmel a nyloc down just for belt and braces.