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Lawnboy gold series: Broken bolt in aluminum block

#1

2strokefan

2strokefan

I found the lawnboy of my dreams, gold series, battery start, self propelled 2 stroke...but the two bolts that hold the coil bracket on were messed up by the last owner. I was able to get one working by tapping the hole. The other bolt is broken off inside, tried a screw extractor, and now it's broken off inside also. Any tricks to get these out ?


#2

StarTech

StarTech

It take carbide to remove broken extractors. They are that hard. ANd you got to start small at the center and step drill out the screw extractor and screw.

I just know don't why people keep trying to use screw extractors for screws that broken off while try to remove them. Extractors are primary used to extract screws broken off while installing them.


#3

sgkent

sgkent

If enough is above the surface you can weld to it. But otherwise it is likely to be a real challenge trying to get it out. Carbide or diamond bit with a drill press. I broke one off in a rare manifold once and took it to a specialty place. They put it in oil and lowered an electrode down to it, then slowly arced it out with the electrode. I rarely use extractors for that reason.


#4

Hammermechanicman

Hammermechanicman

You can try REAL cobalt drill bits from a place like Grainger, not harbor freight. Start small like 1/16" then work up to a drill size where you can tap a new hole.

Good screw extractors are fairly hard to break but where there is a will there is a way. If you break off a steel bolt in aluminum you need to drill out the bolt till all that is left is threads then chase out the threads. The bolt snapped off for a reason.


#5

sgkent

sgkent

Sometimes you can use a small punch to drive it clockwise enough to free up and come out.


#6

StarTech

StarTech

There is also acids that eat out the steel and leave the aluminum in tack but are used by those that know how to handle those strong acids.


#7

B

bertsmobile1

From the start
1) use a Dremel tool fitted with a tungsten bit that is flat on the end like an end mill and flatten the end of the broken item
2) use a lathe centre drill to make enough of a dimple to start drilling
3) use a standard cobalt drill to start drilling out the hole stepping up one size at time
This both makes the hole and heats up the stuck whatever which is handy if corrosion is the problem.
4) swap to left hand cobalt drills used in hammer mode and press down very hard to prevent it bouncing around
About 1 in 5 will will unscrew with the left hand drill .

If this is beyond your skills then ring round the local engineering workshops for one that uses water drills and get them to machine it out for you.
Not cheap but quick and very clean with zero damage to the item.


#8

2strokefan

2strokefan

Wo
bertsmobile1 said:
From the start
1) use a Dremel tool fitted with a tungsten bit that is flat on the end like an end mill and flatten the end of the broken item
2) use a lathe centre drill to make enough of a dimple to start drilling
3) use a standard cobalt drill to start drilling out the hole stepping up one size at time
This both makes the hole and heats up the stuck whatever which is handy if corrosion is the problem.
4) swap to left hand cobalt drills used in hammer mode and press down very hard to prevent it bouncing around
About 1 in 5 will will unscrew with the left hand drill .

If this is beyond your skills then ring round the local engineering workshops for one that uses water drills and get them to machine it out for you.
Not cheap but quick and very clean with zero damage to the item.
Click to expand...
Wow.. what is a water drill ?


#9

B

bertsmobile1

What modern engineering companies use to make production line holes with
It is a very high pressure water jet water jets
Been around since the 70's
Down here we have mobile operators who will come on site remove the broken bit
Not cheap but neither is a big earth moving machine sitting there doing nothing .

There are also laser drills & electo-machining , all used to remove broken bolts amongst other things .

I find it funny that in the land that prides itself in the entrepurerism you do not seem to have any where near the amount of mobile services that we have down here


#10

StarTech

StarTech

We would if we had customers that would pay for the services but we don't.

Here even most of the old automotive machine shops have closed up due lack of business. The last I tried to get engine block processed I couldn't find a single shop in my area that could do the work. All of us old farts are leaving the business and no one wants to take our place.


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