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

ClintBX · Jan 21, 2019

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.

pwd · Jan 22, 2019

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-drill-bit-set-13-pc-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.

999zip999 · Jan 22, 2019

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 · Jan 22, 2019

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.

Jon NCal · Jan 22, 2019

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.

aroundqube · Jan 22, 2019

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 · Jan 23, 2019

Jon NCal said:
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.

bigmoose · Jan 23, 2019

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.

dogman dan · Jan 23, 2019

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

Jon NCal · Jan 23, 2019

ClintBX said:
Jon NCal said:

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.

Click to expand...

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.

mcfizzlestag · Jan 23, 2019

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

ClintBX · Jan 30, 2019

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 · Jan 31, 2019

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

50% experience broken bolt backs out without using extractor

fechter · Jan 31, 2019

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.

APL · Feb 6, 2019

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.

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

ClintBX

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pwd

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999zip999

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ClintBX

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Jon NCal

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aroundqube

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ClintBX

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bigmoose

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dogman dan

1 PW

Jon NCal

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mcfizzlestag

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ClintBX

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kcuf

100 W

fechter

Administrator

APL

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