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Drilling broken bolts from Aluminum casting


mickblock's Avatar
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06-06-10, 07:55 PM   #1  
Drilling broken bolts from Aluminum casting

I was replacing the bearings on my riding mower and snapped three(3) entire bolts out of the six that pass through the deck and thread into the pair of aluminum mandrel housings.

My question to anyone that has ever succesfully salvaged a part in this state is - is it a cut and dry thing or a day long project that - maybe it'll happen maybe it won't?

I do not know what the bolts are made of or what grade because they aren't marked at all. But they snapped pretty easily. Too easily for bolts that cost $4.12 each to replace.

I've already got part #'s lined up to make replacements. But I'd hate to not try. Although sometimes it's nice.

 
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06-06-10, 08:09 PM   #2  
If there's enough bolt sticking out of top or bottom get a good pair of visegrips on it and use an oxy/acet torch to heat the aluminum around the bolt enough to get it to turn a little. Be careful when you see the aluminum start to get shiny under the torch flame. That means it's getting ready to melt!!!
Once you get the bolt to turn, keep rocking it back and forth gradually working it out. If you can't get them out, drill them out to whatever the bolt size is and use overlength bolts w/ nuts. I've never had much luck getting them out w/ an ezy out.
Mike

 
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06-06-10, 08:43 PM   #3  
Depending what the mandrels are worth new,, & what your time is worth,, You may be as far ahead to replace them... You may spend a lot of time trying to get the old ones out,, but you may get lucky!!! It's your call on this one, as I've never had much luck & I've found the replacements are cheeper than the labor to save the old ones... Good Luck,,,, Roger

 
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06-07-10, 07:44 AM   #4  
$4.12 bolts...sounds like you're working on a craftsman?
I agree with Hopkins the easiest fix is to replace the housings. The sears parts direct lists the replacement bolts as 1.00 L x .25 w x .25 h I believe. Not standard a thread pitch. Personally I would not trust re-using the old bolts either or the threads cut into the old housing.
The new housings are usually not tapped either and some require self tapping bolts and when you mix metal and aluminum in that manner, you usually have a one time application.
On new housings I use a standard 5/16"x18 flanged bolt and run them in with one shot using an impact or air ratchet.
To reuse the old one I would simply drill out the old holes and broken bolts to fit a 5/16" bolt, then nut the bottom. Most of the housings do have an inset for a nut.
I would also give the old housings a thorough inspection for cracks on any of the mounting ears. If the bearings were in need of replacement, the housings have been stressed already, and they are not all that stout to begin with.

 
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06-07-10, 05:15 PM   #5  
Good stuff gentleman. Those were all the kind of responses I was looking for. Thank you.
I agreed in advance. So I picked up two mandrel assemblies after work. I'm happy with my decision.
I just can't resist prepping the deck for a couple coats of engine enamel before putting everything back together.
So you can at least tell that it has brand new parts on it.


Posted By: BFHFixit $4.12 bolts...sounds like you're working on a craftsman?
Yes it's a Craftsman LT 1000.
The bolts had no markings because that's how grade 1-2 hardware is designated. But they just hold the whole blade assembly on, and the blades aren't even that heavy. So using a harder grade of hardware would just be unnecessary.

Wouldn't wanna be caught over engineering anything now would we Craftsman?

Picked up grade 8 from the hardware store for 1.29 ea.
'cause that's how I roll.
I'll use the capture indents for the nylon lock nuts and I suppose a lock washer up top will be sufficient.

 
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