Rethreading screw holes

[TomC]

Ok, well I have a knackered screw thread in my engine casing Basically It needs to be retaped. Whats the best place to get something to do this from and what am I looking for? and also how do I identify the the thread that I need?
Is it going to be possible to use the current stud or am I somehow going to have to find a larger threaded one?
Thanks.

[overdog]

How bad is it? If its totally stripped then a Helicoil is the only solution(other than a new casing!)
If its not too bad then run a thread chaser down the hole-thread size will be the same as the other bolt holes in the casing.
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Ooooh-thats gonna leave a scar!

[TomC]

Its fairly bad....

What does this Helicoil do and what does it look like?

[cagiva gezzer]

https://www.emhart.com/products/helicoil/images/heli123.gif

Drill - Drill out the damaged threads using the drill size specified in the catalog. Drill to sufficient depth to accommodate the insert length and bolt or screw being used. Tap - Use the Heil-Coil Tap specified in the catalog. Check the size on your shank to make sure you have the right one. Tap the hole to sufficient depth to accommodate the insert length and bolt or screw being used.
Install - Use the specified installation tool. Just wind the insert into the hole until the top coil is 1/4-1/2 turn into the tapped thread.
Note: Remove tang with the appropriate tool specified.


All you need to know about helicoil kits
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"because one stroke isnt enough and four strokes waste two"

[overdog]

Basically the stripped hole is drilled out to a bigger diameter and a threaded insert put in-the thread of this insert being the same thread as the original bolt.Hope this makes sense!
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Ooooh-thats gonna leave a scar!

[TomC]

Where can I buy helicoils from? as I think this will probably be my best option. A shop that i can go to and have a look for what I am looking for is best as im unsure of what thread etc. So what sort of shops sell them?
Cheers guys.

[Guest]

What bike and screw hole is it, then we might be able to tell you the size

[TomC]

Bike is a Derbi Senda, The stud thread measures 6mm diameter.

[TomC]

Any chance good old Halfords sell them?

[NickD]

Probably. Also B&Q etc, will probably have 'em, and so will most car spares places. Beware though, if it's a bolt that needs doing/ undoing regularly a helicoil is probably not the way forward, but if it's in something that can be bolted up then pretty much left alone, go for it.
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I was only doing what it said on my licence officer....
Tear along the dotted line!

[TomC]

Nar it isnt going to be coming out again..
Well, definately not by me anyway, im selling the bike as soon as I have got the rebuild all done.

[cagiva gezzer]

Kits are expensive, if you only want one, pop down to a local engineering firm. They should be able to do it in a couple of minutes for less than a kit costs.

Where is the stripped thread? Clutch cover?
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"because one stroke isnt enough and four strokes waste two"

[TomC]

Engine stud (to hold cylinder head etc)

Thanks.

[cagiva gezzer]

Sod it, you've got three other studs! (joke)

Ok, how the hell did you manage to strip that and why did you feel the need to remove it?

Reminds me of when we were working on my mates TS50. We tightened the head bolts a little too much. One snapped off so we just super glued it back on. So somewhere there was a TS50 with the head semi glued down.......

I say give it to an engineering firm as the damage that could be done if it failed would be expensive.
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"because one stroke isnt enough and four strokes waste two"

[TomC]

Ideally I wouldnt have removed it, but the nut siezed to the top of it so when I removed the nut the stud came with it. Unsure how it striped however, last time I had the head off, the stud came with it aswel and I can only guess that I didnt fit it properly and once it came out again it just simply wouldnt go back in, it gets a certain way in then just stops and is easily turned but doesnt tighten.

I cant really take it to an engineering firm, for one I cant afford it, and two, I dont know any or have any means of getting a half striped down bike there so I am going to have to do it myself.

If I buy the correct Helicoil and kit then I think I should manage, and I have a local garage that might be of some help, should have gone there in the first place and wouldnt be having this problem.

Cheers mate.

[cagiva gezzer]

You need enough space above the hole to get a power drill in to open up the hole. From memory there isn't that much room between the studs and the frame, so you might have to remove the whole engine.

If you leave it in watch out for swarf getting into the crankcase.
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"because one stroke isnt enough and four strokes waste two"

[TomC]

Yer good point, Cant say I had thought of that. Yet more fun.....

[Big Pete]

m6 Recoil kits run at £16-20, if the thread has been completely torn out you can get away without redrilling the hole, the tap will cope with cutting the new thread size. You do need to keep everything square tho.
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Trust me, I`m an engineer
GarageOfPower.co.uk

[TomC]

Cheers mate.

Know of any shops that definately sell the kits? save me the trouble of searching around.