How to fix stripped thread

the_weaver · Post by **the_weaver** » 06 Jul 2010, 20:10

The thread has been stripped on one of the mounting holes for my lower cambelt cover on my ZX 1.9D. I've got some "CarGo QuikSteel" which is a two part (epoxy?) repair putty. The instructions say something like "fill the hole, leave to dry, drill a new hole, tap the hole". Unfortunately, I haven't got any taps. I was hoping to just coat the bolt threads with paste and undo the bolt as the paste is just drying to improve the existing thread which is still there but not holding the bolt as it's tightened.

Any tips on how best to repair the thread?

Paul

h2ocooler · Post by **h2ocooler** » 06 Jul 2010, 20:20

The only way that would work (but not 100%) is to coat the thread of the bolt in silicone before putting it into the just filled hole. the only problem would be that the bolt still gets stuck.
Proper way is to fit a helicoil but that means buying a kit to do it.
Rob

Post by **CitroJim** » 06 Jul 2010, 20:39

Your idea won't work too well sadly, you'll find any thread left (if any) will be very rough and not up to the job.

If you allow the Chemical metal to fully harden and then drill and tap, the resulting thread will be good for holding a cover but I'd not recommend it for anything seriously load-bearing. If it is, the thread will need helicoliling.

A set of taps are not expensive but you do need the right sized drill to make the initial tapping hole.

You need the set of taps, the two sizes of taper tap and a plug tap to finish.

the_weaver · Post by **the_weaver** » 06 Jul 2010, 21:13

Thanks for the replies. I'll check if the local motor factors sells taps tomorrow.

Paul

the_weaver · Post by **the_weaver** » 06 Jul 2010, 22:02

The bolt is 7mm diameter. Typical of Citroen to use an odd size (like those 35mm hub nuts).

What size drill do I need for a 7mm bolt?

The bolt info is:-

Capscrew diameter 7X100-14

Do I just need to get the three M7 taps or is there anything else to think about like the thread depth or coarseness?

Paul

handyman · Post by **handyman** » 06 Jul 2010, 23:47

If you are going to use this plastic metal repair compound, you will need to drill the hole oversize, otherwise you will just be making a thread form from the plastic, which will not hold.

The perfect, permanent repair is to use a wire thread form insert, Helicoil

. However if you are not mechanically adept, you can make a real bodge and get it wrong.

You can by cheap insert kits that contain a couple of inserts of the right thread form, a tap and the insert tool. It may also include the relevant drill to re-tap the hole.

I think you will find these covers are held by screws with an M6x1.25 thread form, as M7 is non-prefered and even Citroen are not that perverse.

Alternatively, if you are in or near East Sussex, bring the part to me and I'll be able to fit an insert for you as I keep a whole range of wire-formed inserts, including all metric and imperial sizes. I can even do spark-plug threads, in-situ, without the need to remove the cylinder head.

Handyman

f00lzz · Post by **f00lzz** » 07 Jul 2010, 14:57

handyman wrote: Alternatively, if you are in or near East Sussex, bring the part to me and I'll be able to fit an insert for you as I keep a whole range of wire-formed inserts, including all metric and imperial sizes. I can even do spark-plug threads, in-situ, without the need to remove the cylinder head.

Handyman

Well now... that's what this forum is all about!

the_weaver · Post by **the_weaver** » 07 Jul 2010, 20:16

M7 does seem to be a strange size but I got the bolt info from the drawings so it must be right? I bought a new lower cambelt cover to replace the one that was missing. I bought some M6 and some M7 bolts. I'm now wondering whether I tried the M6 bolt in the hole by mistake instead of the M7 and then came to the conclusion that the thread had gone. I'll check again tomorrow and I'll check I'm using the correct bolts this time.

Thanks for the offer to fit an insert for me but as I'm in Wales it's not an option.

Paul

the_weaver · Post by **the_weaver** » 08 Jul 2010, 20:57

I've sorted the problem out. The thread was ok. It was M7 but because the bolt had been missing for a long period the thread in the hole was dirty. Previously I tried the M7 bolt and it wouldn't go in so I assumed it must be M6. The M6 bolt I tried then made me think that the thread wasn't holding properly. I've now cleaned the thread and the M7 bolt goes in fine.

Paul

addo · Post by **addo** » 08 Jul 2010, 23:24

Something you might want to add into your arsenal, is a spraycan of carby cleaner/throttle body cleaner with the extension tube.

It's good for hosing out blind holes like this, and leaves no residue - excellent when you're using a Loctite chaser.

Take note that it is pretty harsh on your skin, especially if you don't have tradesman's hands (as in, already abused).

Stempy · Post by **Stempy** » 08 Jul 2010, 23:59

handyman wrote:
I think you will find these covers are held by screws with an M6x1.25 thread form, as M7 is non-prefered and even Citroen are not that perverse.

Handyman

They're perverse enough to use M9 rear caliper bolts, and you don't get much more perverse that that

the_weaver · Post by **the_weaver** » 09 Jul 2010, 13:19

Thanks for the tip. I've got some carburettor cleaner somewhere.

Paul