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Old 24 February 2009, 04:13   #21
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Couple of helicoil tips - if you are replacing an M6 be sure your tap for the coil thread is M8 fine - M6 has a 1mm pitch, M8 (standard) is 1.25..... Also get a bottoming tap for the final cut that you inevitably won't get in the kit - as it's a head bolt it will be going into a blind hole. Also use a stainless coil, then you end up with the thread against a similar material, so when it corrodes next time it just anchors the coil in place & the bolt / screw should release more easily, as opposed to 6 months later being doomed of ever getting it out again as the mild steel coil codrrodes.

Now for the warning, remember the stainless screw remains will not take kindly to a drill going too fast and will just surface harden if your drill is spinning too fast. So, make sure it's a sharp bit, and be very careful to make sure you get a constant stream of "chips" off it, otherwise your life will become very difficult very quickly as your snapped screw shank becomes an impenetrable shield.....

Good luck.
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Old 24 February 2009, 04:21   #22
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a good unworn jacobs chuck can sometimes get into awkward places a molegrips wont too.
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Old 24 February 2009, 06:39   #23
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OK, two options here.

Option one is the safest one. To leave the 4 bottom bolts in and to extract the upper ones. I would suggest a little drill guide to fit into the clearance hole of the lid. Then drill the bolt so that you can use an easy out. The heat from drilling coupled with the plus gas should break the corrosion sufficiently to enable extraction. You then screw in the easy out (a left hand helix tap) and hopefully should extract the stud. Easy out

The second is a little more risky as it involes removing the bottom bolts. First you must remove the bolts without snapping them. Plus gas is the first step the second would be heat but might I suggest doing the bolts up first. Yes really! The action of doing bolts up will make them shrink slightly and thus break the corrosion enough to be able to undo the screws normally. This might well be possible without the heat but you will have to have a steady hand and nerve Your experience from the other bolts snapping will help you here. Once the bolts are removed then you could try the hole grip method or the easy out method, it's up to you.

I have some easy out's but because of your location makes it difficult to get them over to you. Try tapping up some machine shops on the Island they might well lend you a set for the return of a holding deposit.....Tell em your a cash strapped Student
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Old 24 February 2009, 07:32   #24
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Listen to dirk!

A propane/butane flame is fairly cold, unlikely to cause collateral damage unless yer silly. Get the studs/bolts as hot as the propane torch will allow - should be at least straw coloured on the stainless. Get the remaining 4 out with heat, then heat on the studs to remove the remaining ones with mole grips.

Drill should be a last resort, as you need a kryptonite drill bit and drilling stainless is a pain. The chance of it wandering off centre into the soft ali is high. If you have to drill, start with a small size and work up slowly- if you can keep the drill centred, you have a fair chance of getting the studs out without needing to helicoil.
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Old 24 February 2009, 08:01   #25
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You then screw in the easy out (a left hand helix tap)
If you decide to go the "easy out" route, then buy one from your local snap on man, otherwise you'll be starting the "How do I get an easy out out" thread pretty soon!
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Old 24 February 2009, 08:25   #26
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Yeh. I've never ever had an easy out work for me - but I've never had a snap-on one.
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Old 24 February 2009, 08:26   #27
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Drill should be a last resort, as you need a kryptonite drill bit and drilling stainless is a pain. .....


.... If'n yer a Girlie.
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Old 24 February 2009, 08:31   #28
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Damn right!
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Old 24 February 2009, 08:34   #29
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The bolts are not stainless if that makes any difference. Some of the snapped bolts are extremely corroded leaving hardly any material intact so I'm not holding out much hope in getting the remaining ones out.

Matt, am I not supposed to be heating the casting as opposed to the bolts? Heating the bolts would just expand them in the holes making it even more difficult to get them out wouldn't it? Or does the extreme expansion and contraction of the bolt tend to release it?
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Old 24 February 2009, 08:42   #30
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Oh shit! On the spot now.
The expansion rate of the ali is higher than the steel, that's the point of heating it. You do ideally want the bolt/stud cold, but it's generally not practical (cue sarcarstic remark from lofty ), and the colouration of the steel bit gives you an indication of the temperature.
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