Scooterotica

Double nutting and heat was not working. But this did for 3/4
- heated case with yellow map gas
- inverted a can of air duster and blew on the stud near the base. The propellant comes out cold enough to freeze flesh. This made a massive thermal difference
- put penetrating oil on to let try and soak in
- double nutted the studs and tapped on the nut with a hammer to try and help break the corrosion bond
- used a stud removing tool. Kind that grabs the base and uses a 1/2 in ratchet.
- turned it in first, then out

3 out of the 4 came out. The last one snapped. So I drilled out starting with a small bit and jumping 1 size until I got close to the threads. Then tapped out starting at m6, m7, then m8 X 1,25 . Use new titanium bits and lots of oil. When tapping the motion in a bit forward then back off. Repeat.

A pain in the ass but if I wanted an easy life I'd drive a Honda.

DD.

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Wow. I had been fighting with this completely corroded plate for days. Screw heads mangled. Map gas under neath, inverted air duster on the heads, a tap on the impact driver and they backed immediately out. About 15 mins of work. My new favourite trick.

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Ever tried an anticlockwise drill bit? Had a snapped at base exhaust stud , filed flat, dot punched centre, spun out...

They do work for sure but not always in the worst case. I once snapped a screw type extractor before. As it is harder than a bolt you can't drill it out. I ruined the part.

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Alternatively, for studs that have sheered off flush or taps that have broken off inside deep holes, I've been using spark erosion. When machining some of the GT cases I have broken M6 taps on the CNC. The tap snapped in the M6 seal plate hole in the crank case. You'd have no chance to get this out normally but with spark erosion no problem at all, even the original thread was intact! If you've had a major catastrophe get in touch before diving in with a grinder.

Had not heard of spark erosion before. Something new to research. I reach for heat and freezing as the starting point as ALU heats 2x faster than steel causing different rates of expansion. Then hit the steel with cold to cause it to contract. If that doesn't break a rust bond you are seriously stuck.

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This tool can work well on a broken off tap.

http://scoot.net/gallery/bbs/DSC01064.JPG