Broken blade screw inside in crank-shaft

Hello, I'm hoping someone can give me some ideas on how to fix my Husquavarna HU800AWDH.

Since my kids are out of school, I was eager for them to start helping mow the grass. Sure enough, the first day my teenage son mowed he hit something in the yard (a tree stump, I think).

The blade screw broke off inside the crank-shaft. Unfortunately, where it is broken is recessed into the shaft. Attached is a picture. Any suggestions on how to get this thing out?

The markings you see on it is drill marks from me trying to drill a slot into the screw in order to get a flathead screwdriver on the top of it. So far, no success.

Several methods are possible being the screw is basically loose. For the least expensive try drilling 2 holes about a 1/16" in diameter and about 1/8" deep. Keep the shop vac close to the drill bits to vacuum any cuttings while drilling. Insert a couple of drill bits in the holes and place your screwdriver between the bits while holding the bits together and screw it out.

EDIT: On second thought, it may pay to do a shaft run-out check for concentricity to determine if the crank is bent. If it looks good in that respect proceed with the bolt.

At least you have a son that will try so I give him credit and this is a lesson he'll never forget as he may in book learning.:thumbsup:

Get a left hand cut, left hand spiral drill bit that's about 1/3rd of the diameter of the bolt. Center punch as close to the center as you can and start drilling. It will probably unscrew while you're drilling. If not, then get an EZ-out to take out the broken bolt.

LHC, LHS drill bits are available at places that sell machining tools and supplies. Online at McMaster Carr or MSC Direct.

It will depend upon what tools you have on hand.
Starting with the easiest, after checking that the shaft is not bent as previously mentioned.
1) get a center punch and tap the bolt at the edge at a left hand tangent.
Blade bolts usually unscrew easily once the head is broken off.
You might like to heat the shaft , a hot air gun will be fine and hit the hot shaft with some of your favourite penetrating fluid .
keep putting it on till the shaft cools so the penetrant will get sucked deep into the thread.

2) As you have made a right royal mess of the end, a Dremel type tool with a tungsten cylinder tool to clean that mess and make it deeper with squarer sides
Then use an impact driver bit, either in an impact driver or held in a wrench while it is struck on the end with a hammer, don't over do the hammer I said TAP

3) as previously mentioned, the left hand drill.
Start with a lathe centre drill ( normal right hand ) then go to the left hander
I find if I use them on the hammer function on they will generally

From the look of it you still might have to clean the end up a bit from the attempt the cut the screwdriver slot

4) If you have an arc welder handy and can actually use it weld an old Allan key to it and turn that.
After the weld is done, hit the thread with the penetrating fluid & wait till it is dead cold before trying to turn as the bolt will have expanded from the welding heat.

If the shaft is bent, they have been bent back but it is a risk. You may damage the bearing in the process. But for the most part it is considered scrap so you don't have much to lose. I have bent them straight by hitting with a small 4lb hammer while using a block of wood on the shaft to protect it from deforming. You do not have to get it perfect to be good enough. IMHO.

If it is not bound up in the thread you may be able to knock it around with a sharp center punch and hammer. I would try that 1st. Some people even use and Air hammer with the appropriate end tool to do the same thing. The air hammer may cause the crank to turn so you may have to hold it with a pair of vice grips or similar. Heating up the out side shaft may help. The slot you tried to cut may actually help.

Welding an Allen key or small bolt to the shaft end is probably the next easiest and quickest assuming you have access to the right welding equipment. Other wise I would try to drill on center with a left hand drill and then try an "easy out" with heat applied to the shaft. (Yes, start with a center drill or small diameter drill to get the hole started) Use plenty of penetrating fluid. It may be rusted on there. As someone said if it is not bound up it may unscrew just from the force from the left hand drill turning.

Good Luck and let us know how you make out.