Thread Inserts

Well, as previously reported the studs are out, but have 2 cylinder head stud holes in the casing that require mending.

First has anyone made this repair and how did it go?

My thoughts go to "heli-coil" and "time serts" (threaded bush). A few reports don't seem too keen on heli-coil which I tend to agree with, the "time sert" bush looks better but more expensive for the repair kit. I did see on here I think pete1950 did a brass insert repair but don't think there is enough material to drill out that big.

Anyway thoughts and experiences on a postcard, thanks in advance.


Cheers Gaz

 

Thanks to both for replies.

I would use a heli-coil on the part of the casing which was used for fixing a bracket to or holding a cover on but feel the cylinder head stud is different senario.

If there are people out there that have used a heli-coil to repair a thread in this area sucessfully I would consider using them, but various internet searches reveal that many have come loose, most were car cylinder heads.

I suppose I am answering my own question. I just wondered if anyone had done this repair. If you look at the cross section of a heli-coil repair the wire coil sits in the groove of the bigger tapped hole and leaves a gap between the coils. The Time serts is a solid bush. I feel there is probabley more contact area with the Time sert and as well as locking the bush in at the bottom with the installation tool this extra area can be filled with loctite. Final torque for head nuts I believe is 41/42Nm, I am going to try and put a bit a theory behind this to ease my worry.

Thanks again.

Cheers Gaz

 

Many thanks for replies.

I had a look and yes it is a long way, I don't go that far on my holidays. I don't really trust posting either. Frozen North it was 25 up here today - beautiful.

I am happy with my engineering ability to do an accuarate job putting the insert in at the right depth, square and not breaking thro', if I thought I could not do it I would be straight to an engineering company. My Dilema is, will it vibrate out. I suppose I can overcome this with a bearing retainer high temp loctite.

The bush insert if used will have an O.D. of probably something around 12mm which will give take approx 1.7 times more torque from general max torque figures for M10 & M12 so it should not pull out of the casing before stud pulls out of the insert.

My thoughts are if I could get a stud with M12 on it and tap out the casing to M12 this could be assembled as normal. So rather than locking the the insert in the casing I could lock it on the the stud and assemble as normal. If anything happened hopefully the insert would come out with the stud and I would not end up with a drill out operation in the casing.

The Keensert say you need a boss dia 1 1/2 x O.D of insert. The casing has a boss of 20mm so no good for Keenserts which is M16, I thought they looked a bit big.

I can't see BLR drilling out as much as they did with your spark plug repair Pete (although I need to enquire) as there is not enough material. I have had a time sert repair on a VW Beetle for the spark plug and it was OK. I don't think the pull out force on the spark plug is anywhere near that on the studs.

I was really hoping someone would have done the repair with an insert and could tell me "don't worry it will be fine". I think I will do a few test pieces with time serts.

Thanks all.

Cheers Gaz

 

1037sps

Thanks, its always good to hear some practical experiences.

Cheers Gaz

 

RG

Thanks for comments. My thoughts are Time certs look a bit more robust. Reading a few peoples reports on web sites (mainly car cyl head bolt repair) I came across a few comments about heli-coil coming out, not sure how true this is. I would of thought when the torque and load is on the stud and insert it should be OK eventhough loctite seems to be used by may people. (Also when loctite is used I have seen it quoted that the head should be assembled and torqued and then the loctite sets rather than putting the insert in, letting it dry and applying the torque, comments are this could break the loctite grip).

I took some measurments but I can't find my drg but I was going to use the 24.5 long insert which is the length of the thread and undercut, also the stud shank is set down 4mm and hole depth is 33.5mm (just been out to measure). So we have 5mm ish to poke through to secure the insert. I had wondered about how much force this would put on the casing, the boss down into the casing is 20mm dia. I can't find any time sert edge distances but Keenserts say 1.5 x insert dia. I thought about tapping the insert out and not using the locking feature and using loctite. I also thought that if I put the loctite on the stud thread (which is replacable) and rely on the preload stopping the stud and insert coming undone as it would normaly do on a single piece stud. Anyway I think too much.

I have ordered some inserts (time serts). I think I found out the outside thread is m12 x 1.5 (fine) even though they supply a special tap (have not got the kit yet). Will confirm when I have the inserts. This also could be same for Heli-coil but will have to check. There is a guy on ebay selling a BMW repair kit (M10 X 1.5) in his video he uses a M12 x 1.5 tap for inserts.

Cheers Gaz

 

PeterT,

Yes I did think of that.

Not sure which thread I said the studs were stainless but if I did it was information I got from other web sites and I think it would have been in relaton to the original studs. These were too brittle and did not have the correct elastic properties. The new ones are black so would guess they are not Stainless but do not know the exact material spec. I have already bought new studs before I f@@ked the threads so will continue with the insert plan. In any case I would be unsure of quoting the correct material spec to someone to make some with M12 on the casing side of the stud.

Cheers Gaz.