Advice on removing snapped s/s bolts from alu block

[captbillc]

stainless can usually be drilled using a lot of pressure & slow RPM.

[sailordave]

Couple of things you want to do.
First heat it very slowly w/ a propane torch. Do NOT use a MAPP torch (too hot) Don't get it so hot it turns color, just heat it up.
Take a ball peen hammer and tap gently all around the broken off piece. Spray some PB blaster or other type "stuff" on it. Tap some more.
Let it cool a bit and then try using a LEFT hand twist drill bit. You'll need a cobalt bit to drill into the SS. Start w/ a smallish bit and after you get some depth, go back and use a slightly bigger bit. If you're lucky the drill bit will grab and twist it out. More than not however, you'll have to drill enough to get an easy out in.
Keep heating and cooling. The difference in the metals may eventually let it break free.

Nothing wrong w/ using SS and AL. Just need to make certain you smear some TEFGEL on the fastener to isolate the metals from each other.

[Geoff54]

You have lots of suggestions - which ones might work really depends on the exact circumstances. If you try to drill it out invest in some left handed drill bits.

There is another alternative that save my as* a few times, including the time I snapped off an extractor, inside a hardened stud, inside a magnesium casting. It's called spark-erosion and works just as the name suggests.

It's not cheap and there aren't many places that do it (I only knew of one in the LA area when I lived there) but if you can find one locally, it's the best way to go for difficult extractions.

If you can't find anyone, ask around old fashioned motorcycle shops, classic car/motorcycle restorers, machine shops that rebuild engines (especially exotic engines), etc.

Good Luck

[Brewgyver]

Another quick note. If you're going to try this yourself, the biggest problem with drilling is that the screw is frequently broken off unevenly, and the drill bit will walk right off of it. Use a center punch (a real center punch, not a nail, not a nail set) to dimple the exact center of the screw.

[Sea Dawg]

Sailordave has it right, except MAPP fuel may be necessary if the aluminum carries too much heat away. YOu want to get it pretty toasty and spray the PBbuster on while it's hot and the quick shrinkage can create more crevice between the bolt and threads. Also, the center punch is necessary which can also shock the bond between the threads. Lastly, there is a impact driver that will transfer hammer blows into rotation and doesn't cost much to try. You'd have to chisel a flat head slot to get a grip. Heat, cool, shock, repeat. IT will come out.

[TQA]

hEAT IS GOOD.

[MarkSF]

Thanks everyone, I have all the tools on order, so I'll try it when they arrive (reverse drills, extractors, hole punch, etc)

[wduncan50]

You might try this from Loctite: Welcome to: Loctite® Freeze & Release

I don't know if it works but I know I tried heat once on a SS bolt in a traveler (alum) and still broke the bolt after heating and spraying with PB several times over a couple of days.

[tommays]

You pretty much screwed yourself not using heat and patience in the initial tear down don't screw your self up even worse learning to drill out small SS bolts on something that will become JUNK if you get wrong as there is NO room for error

[Sal Paradise]

I have experience with this. You will have to drill the old bolt out starting with a very small bit.Use titanium bits. For an M6 get 3 bits the largest bit the same size as the bolt. Then get a NAPA helicoil kit. It includes a special size drilland tap. It will be easier than you think, just follow the directions. You thread the helicoil into the new threads and then use a new bolt. Motorcycle mechanics know all about this. Its a very common repair. I have done this and it works.

Easy Outs are crap and don't work!