Stripped Bolt

[Agfoxflyer]

Today in trying to remove my gear box, I removed all of the metric hex head bolts but the last one. It is one of the larger bolts at the bottom of the gear box. Unfortunately I stripped it out. Would a screw extactor work? The torgue value of these bolts are pretty high. I thought about cutting a slot in the top of the bolt and using a large screw driver. Any help or advice would be appreciated. Oh the engine is a 912ULS.

[Breathless]

I have cut slot into the head before with good results. I used a Moto tool(Dremal) with a small cutoff wheel, then used a flat bit driver that fits tight. Sometime a sharp blow with hammer to the driver. If the bolt has been installed for a long time, I heat the fastener before trying to remove.
Extractors would be my next thing to try. But if you haven't used them before the correct size drill is very important. I use a small drill bit first to keep in the center of the bolt.
Good luck

Jim

[Av8r3400]

If you are talking about a socket head cap screw (Allen head - that's what is on my 912's), you can often tap in a high quality "Torx" driver, of the appropriate size, into the stripped socket hole and it will bite enough to remove the screw.

If you can find one, I've used impact torx sockets like this with good results.

[Mark]

I have used 'easy outs' with good success. Also, heating the bolt will help loosen any thread locker on it.

[t j]

There are some allen head bolts in the Rotax gear boxes that are not your ordinary allen head. Using an ordinary allen wrench will risk stripping them. You need an "Allen key with pilot". There is a nose on the end of the wrench that fits into a hole past the hex hole in the head of the bolt. This keeps the wrench absolutely straight in the hex hole. Those bolts are very hard to get out as they probably have some exotic and expensive lock tight on them.

Here's a picture of the allen key with pilot
http://www.ekmpowershop2.com/ekmps/shops/conairsports/277817-allen-key-with-pilot-hole-gearbox-types-b-c-e-613-p.asp

[Slyfox]

those bolts must have locktite on them, than again it just may the case of aluminum and steel bolt syndrome. If you stripped out the head, do what you can to get a hold of it, I'd have to look at mine to see what your talking about. But before I tried removing it I would heat it up good to melt the locktite or other, if it were me I would use a oxy torch get the bolt red and than try again. I've had to remove many a bolts that didn't even have the locktite with the housing aluminum and that was the only way. I also found another trick and that's to heat the head up red and than smack the screw or bolt with a punch or socket on the head with a hammer. You only want to go until the head turns read don't let it melt down.

[SkyPirate]

I've had to weld a bolt with a hex head to some allen head bolts to get them out,.which puts heat to the bolt in the aluminum at the same time but gives you a more solid bolt head to turn,..like Slyfox said as well ..smacking the head of the bolt that's stuck sometimes jars things enough to losen the bolt too,.. just use a punch tool to avoid smacking the casing ..cast aluminum can snap pretty easily if a other then designed load is applied..
I'd re install a couple bolts to hold the housing from moving until I got the bad bolt out.

Chase

[Slyfox]

some more tricks I've used, after heating up the bolt, very important, I have used a chizel and angle it and hit it in the direction to loosen, Also if you can get a small pair of locking plyers on the head, that works also. Sometimes you can grab either the allen head either in metric or standard in a slightly bigger size and hammer it into the hole. You can also take a torx head and try putting it in there. I work on transmission and there are times that I run into the same thing and the only way to remove the bolt is to heat it up and than remove.

When you first try to remove the bolt if it's in there tough, that's the time to head up the bolt before stripping it out. I love my oxy tanks for that stuff. Oh and don't use the cutting torch, use the smallest tip you have, the one I like has a 0 on it. The 5 is a little to big and adjust for the smallest flame.

[Paul Z]

I would recommend heating the bolt up, then tighten it to break the loctite bond, and to prevent stripping the hex in the loosening direction, then loosen the screw. Be cautious not to overtighten especially in aluminum.

[Slyfox]

I found that a 6mm hex head socket is the right one, the 1/4 size is a little bit bigger, you might be able to hammer the 1/4 hex socket in there to get it out. If not find an easy out. But heat it first.

[Av8r3400]

A T-40 torx bit is .260" from point to point.

A 1/4" (.250" flat to flat, .289" from point to point)

A 6mm (.236" flat to flat, .272" from point to point).

This makes a t-40 an excellent tool to tap into a stripped 6mm socket head cap screw. The torx bit will hold much more torque than a hex shaped socket.

Give it a try and see.

Some heat is good to release locktite, but heating the aluminum is dangerous. It may damage the case if too much heat is applied. Never use a torch on this application. Heating the screw itself will only make it expand and get tighter.

Heat the whole area with a heat gun.

[Slyfox]

sorry i disagree totally on this. I been doing transmissions for 30 years and have been using my techniques for as many. You must be going on theory on what you say. If you are careful and use a very small tip you can heat up the head of the bolt and it will come out. I can prove it through having to do it. Sorry guy.

Now this is my theory, you heat up the head with a torch, you concentrate the heat right at the head. Sure the bolt will expand, but, what I think is important here is the head releases itself from being a clamping force on the parts. So now you have just the bolt to turn out. I don't remember the bolts having locktite on them when I did my gearcase on the 912ul, but that might have changed. With my procedure that to will be taken care of because it doesn't take much heat to release the locktite. So tell me, did the bolts you did take out have locktite? It should be a white look and caked up on the threads, not only that the bolt will come out tight all the way out.

If you are skepticle just put small amounts of heat at a time to the bolt and try unscrewing it, if it doesn't work, add a little more heat. Years ago I thought like you and fought with removing bolts that stripped the heads, than I grabbed the torch and started getting them out.

steve

[Av8r3400]

Do as you like. Personally I wouldn't get anywhere near my $20k motor's gear case with a torch, but that's just me.

In 30 years of tranny work, I'm very surprised you haven't used the torx bit trick. That's not theory; it works very well. (Almost 20 years of being a machinist.)

[horsepower]

Believe it or not it works,I cant say that I have tried it on a aircraft part but do it all the time on outboard motors.If you heat just the head of the bolt the aluminum will pull the heat away from the bolt real fast while actually shrinking the bolt and expanding the threaded hole that the bolt is in.The key is to have all the tools ready and timing is everything, dont dilly dally and most likely it will come out.There are other ways to do it but this is the method I use.Good Luck Randy

[SkyPirate]

I've use heat also on bolts to remove them,..on race cars ,. airplanes ..bull dozers,.. excavators ,,it only cost 500K for a john deere 992 excavator,..don't worry about the cost ..just use the method that does the job right because what ever it is your fixxing isn't worth anything if it isn't working properly

Chase

[Paul Z]

Don't heat it up like you are trying to weld it, and keep the Center of the flame on the Allen Head. All you are trying to do is heat up the bolt not melt the aluminum!

[Slyfox]

I use torx bits, allen bits and those grippers that go around the outside of the bolt. Whatever grips. But you have to heat up the bolt or you will loose the war.