How best to drill through bolt in Stihl hedgecutter head?

[madmaxtree]

If cobalt drills aren't doing the trick, you might wanna grab some titanium-coated or black oxide HSS drill bits – they can handle the hardened steel of those Stihl bolts. And you're spot-on about carbide drills, they're beasts for rough stuff, but for precision cutting, you're better off with the HSS ones.

[spudulike]

Drills vary in quality....I did ask what manufacturer it came from. Our toolmakers always used Dormer but running to a budget, I have found Heller to be very good and not too expensive. 

Those screws are not that hard. Cobalt drills will go through a chainsaw bar easy enough.

[Steven P]

Back to a comment earlier about the drill bit skating about - how about a small pilot hole so the larger one gets something to anchor into or punch a dent in it - again to give somewhere to stop the bit moving about?

[aspenarb]

If you are drilling and have access to a lathe @openspaceman was on the money with a drilling bush, next best thing are these two bob hole transfer punches, a bit of a life save if you want to centre on a broken bolt/stud deep in a hole.

 

Bob

 

 

 

[woody paul]

If you are going to use them tapered extractor them don't as bolt is to small you will lock it tighter in hole and maybe brake it in bolt then you will never drill it out. You will be better off using a torx bit out of screw driver set and drive it into small hole. 

[Cordata]

2 hours ago, spudulike said:

I reckon that once the drill bites, the screw remains will unscrew as you drill as the screw remains will be under no tension.

2.5 - 3mm drill up it with an easy out in reserve. Relatively easy job.

You can sharpen drills very effectively if you have a bench grinder and know the basic angles of a drill head.

 

 

So I didn't read this thread until now, having already tried the carbide bit this afternoon

 

It did exactly what you said here, and to my surprise the bolt almost instantly flew out the threaded hole - no need for bolt extractor at all!

[skc101fc]

2 hours ago, woody paul said:

If you are going to use them tapered extractor them don't as bolt is to small you will lock it tighter in hole and maybe brake it in bolt then you will never drill it out. You will be better off using a torx bit out of screw driver set and drive it into small hole. 

Yep been there with an eezi-out snapped off in the hub flange of my landrover.  Hidden from the vehicle test inspector with a bolt head riveted over from the inside for 15 years now. Not a chance of drilling it out - I tried with drill bits skating all over the surface, then snapping. Will one day buy a complete new hub for it !

[pleasant]

You will be surprised actually how untight that sheared off thread is in that housing. I sheared a head off one of those torx bolts in exactly the same place but on the earlier all unpainted alloy version of those and I simply just wound the broken part out the other side it was littke more than finger tight once the head had sheared

[Dan Maynard]

9 hours ago, skc101fc said:

Yep been there with an eezi-out snapped off in the hub flange of my landrover.  Hidden from the vehicle test inspector with a bolt head riveted over from the inside for 15 years now. Not a chance of drilling it out - I tried with drill bits skating all over the surface, then snapping. Will one day buy a complete new hub for it !

I think spark erosion is the best/only way to drill it out, but may be more expensive than a new hub. 

[aspenarb]

Drilling/helicoiling is ok if you take your time and set up properly and put a bit of thought into it, stabbing away with a drill will end in tears. The drill will need a guide bush if in a blind hole or jig plate.Had to do this lot on the truck a while back, not a single bolt was going to undo, all forty of them had become one with the hub and the heads had to cut off with the gas axe.

 

 

 

Made up a drill jig with dowls to locate on the new disc.