I broke a bolt in my hub motor. How do I get it out?

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ClintBX   1 kW

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I broke a bolt in my hub motor. How do I get it out?

Post by ClintBX » Jan 22 2019 2:48am

Hi ESFMs,

A while back, I was swapping out a motor into a newly laced wheel. While I was tightening the bolts on the covering plates, I made the mistake of applying too much tension on one of the bolts and broke off the head.

How do I go about taking this bolt out so I can replace it with a new one? I tried the Dremel hack so I can unscrew with a Flathead but it's cutting a groove into the surrounding and I don't want to compromise the seal.

I'll provide a pic soon.

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pwd   1 kW

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Re: I broke a bolt in my hub motor. How do I get it out?

Post by pwd » Jan 22 2019 10:50am

Hi Clint,

the hacksaw/flathead screwdriver is a good trick; but it sounds like you may need to try a screw extractor bit with some left hand drill bits. Sometimes, the left-hand drill bit is enough to spin the screw out. The challenge will be finding the correct size left hand drill bit and/or extractor.

Drill bits like this:
https://www.harborfreight.com/left-hand ... 61686.html

Extractors:
https://www.amazon.com/dp/B001D1FXDE/ref=dp_cerb_3

Failing that, if you have access to a welder; try welding another screw, nail, bolt etc to remains of your bolt. You can then use some vice grips and unscrew it slowly with even turns.
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999zip999   100 GW

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Re: I broke a bolt in my hub motor. How do I get it out?

Post by 999zip999 » Jan 22 2019 11:05am

You can get away with one less srew if 7 or more on cover.
If you are going extract file the top of the shank flat. With a center punch find the very center of the screw you need to use a center punch before you try to drill a small hole. Now one size bigger if needed . The extractor must be straight up and down not crooked not crooked.

ClintBX   1 kW

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Re: I broke a bolt in my hub motor. How do I get it out?

Post by ClintBX » Jan 22 2019 3:06pm

Alright! I've ordered a cordless drill with several drill bits. Hopefully there will be one small enough for this.

Here's the pic of what I'm working with here.
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Jon NCal   1 kW

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Re: I broke a bolt in my hub motor. How do I get it out?

Post by Jon NCal » Jan 22 2019 3:23pm

Since you did make a slot, you can now take a screwdriver and hammer and try to unscrew it by tapping on the edge of the slot at an angle to unscrew. I have done this before and it usually works.

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Re: I broke a bolt in my hub motor. How do I get it out?

Post by aroundqube » Jan 22 2019 4:56pm

Once you have the hole drilled, and the screw extractor tapped into the hole with a hammer, I find that it helps a lot to add low viscosity fluid ( ether / starting fluid , acetone ) to the screw threads before turning the extractor.

ClintBX   1 kW

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Re: I broke a bolt in my hub motor. How do I get it out?

Post by ClintBX » Jan 23 2019 3:07am

Jon NCal wrote:
Jan 22 2019 3:23pm
Since you did make a slot, you can now take a screwdriver and hammer and try to unscrew it by tapping on the edge of the slot at an angle to unscrew. I have done this before and it usually works.
The slot is not deep enough and my screwdriver keeps slipping off when I try to turn.

I think I should have sanded it flat before creating the slot. I'm not sure if you can tell by the photo but the upper half of the slot is actually raised higher than the lower and that's why I can't get traction with my screwdriver.

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Re: I broke a bolt in my hub motor. How do I get it out?

Post by bigmoose » Jan 23 2019 8:02am

Here is what I do for broken screws/bolts on really expensive things. It takes a mill (Bridgeport) however, but you may be able to adapt.
  • Lock the part down on the table with fixturing.
  • Take an end cutting end mill and make the top of the broken screw perfectly flat
  • Use a center drill and your skill to find the exact center of the broken screw/stud/bolt
  • Using LEFT HAND drill bits begin to drill the screw/stud/bolt out
Often times when the drill is about 75% of the screw/stud/bolt diameter the remaining broken off bit with screw itself out with the drill. Its hard to describe, but once you get the left hand drill started and in the center, you "bump" the bit into the screw/stud/bolt to make it grip/snag a little harder. Not so hard to break the drill though. Its a touch thing.
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dogman dan   100 GW

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Re: I broke a bolt in my hub motor. How do I get it out?

Post by dogman dan » Jan 23 2019 8:05am

I'd just ignore it unless you get two of them next to each other. But drill and use and easy out will work.

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Re: I broke a bolt in my hub motor. How do I get it out?

Post by Jon NCal » Jan 23 2019 12:48pm

ClintBX wrote:
Jan 23 2019 3:07am
Jon NCal wrote:
Jan 22 2019 3:23pm
Since you did make a slot, you can now take a screwdriver and hammer and try to unscrew it by tapping on the edge of the slot at an angle to unscrew. I have done this before and it usually works.
The slot is not deep enough and my screwdriver keeps slipping off when I try to turn.

I think I should have sanded it flat before creating the slot. I'm not sure if you can tell by the photo but the upper half of the slot is actually raised higher than the lower and that's why I can't get traction with my screwdriver.
I don't mean use a screwdriver as a screwdriver. What you can do is knock the upper edge on the right side with the screwdriver and hammer to turn it counter-clockwise a little at a time by giving it a few taps. It is much easier and quicker than the drilling method.

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Re: I broke a bolt in my hub motor. How do I get it out?

Post by mcfizzlestag » Jan 23 2019 2:34pm

My rack snapped off its screw mount the other day, what worked for me was using a spring loaded center punch, drilling a hole and using a bolt extractor. Thankfully i was lucky enough to harass the millwrights at work to lend me the extractors :D

ClintBX   1 kW

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Re: I broke a bolt in my hub motor. How do I get it out?

Post by ClintBX » Jan 31 2019 2:19am

Alright, thanks for the advice guys. I have extractors and a center punch. I'm still waiting for my cordless drill. I'm gonna just try the conventional method first of drilling down the center and then using the extractor piece.

I'll let you know how that goes. I also have 2 broken bolts in my stand I want to try this on.

kcuf   100 W

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Re: I broke a bolt in my hub motor. How do I get it out?

Post by kcuf » Jan 31 2019 9:40am

try reversing the drill bit after it begins cutting into the bolt

50% experience broken bolt backs out without using extractor
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Re: I broke a bolt in my hub motor. How do I get it out?

Post by fechter » Jan 31 2019 1:57pm

I'd try making the slot a little deeper with the dremel and try unscrewing it with a small flat blade. You can always use a little silicone to seal it when you are finished. If the slot just doesn't work, then go for the drill but keeping the hole perfectly centered is challenging.
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Re: I broke a bolt in my hub motor. How do I get it out?

Post by APL » Feb 06 2019 3:22pm

A few more tricks for such things, is to use a soldering iron and a few drops of PB Blaster applied directly to the
screw head, several times, to expand and lubricate the screw, prior to extraction. Also the use of a cyro, or freeze
spray canister, to contract the screw may help. (just on the screw) Be careful, because the magnets are close by.

Otherwise, if you don't care about looks, and can't get it out, you can always just drill another hole next to it, tap it,
and install another screw.
But since the cover has a lip on the inside, the screw isn't centering it, and you can get by without it.

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