There is a stainless steel bolt (about 3/16 diam) that
is threaded into the center of the motor shaft in an old
dishwasher that I am repairing. In order to remove the
impeller and other parts for replacement, it was necessary
to unscrew the bolt. Having no success, I ground the head
off, thinking I could then liberally apply penetrating oil and
eventually get the bolt out by turning it with a vice-grip.
Despite numerous oil applications and twisting to the
breaking point, the bolt has refused to unscrew.
It is very important that the bolt not break off, as it
would be very difficult for me to redrill the hole concentrically.
Would it be worth trying to heat the bolt with a propane
torch? How should this be done, and what would the risks
be? Would there be increased risk of shearing the bolt off
after heating (assuming it still won't yield at the threads)?
Your advice is appreciated. I will tell you that I do have
a backup plan to extend the bolt length with a collar, but
this is not optimal as it will require enlarging the center hole
on the impeller and other problems. (This of course assumes
the current bolt remains unbroken.)
Thanks very much. (Don't hesitate to recommend the
backup plan if you really feel that it's the best route.)
I used to run into this all the time in my former business. Heat the bolt
till it's cherry red and then splash cold water on it.
The bolt will expand with the heat and contract with the cold. It'll come
out like a baby.
On 1/16/05 10:52 PM, in article email@example.com,
You need to heat the motor shaft instead of the bolt. The idea is to
expand the shaft so it will release the bolt. It might help to heat the
shaft then dump water on it to cool it rapidly. Reheat it, then try to
unscrew the bolt.
Propane might not be a hot enough fuel. I'm used to using an acetylene
torch for these type problems. There is something called a mapp gas torch
that is fairly cheap and would produce a hotter flame than propane.
I was also going to suggest Mapp. Much hotter than propane.
Also: Heat the shaft, then spray a tiny bit of water on the bolt. Goal being
to cool the bolt. Then try loosen with vise grips on the bolt, and
channelocks on the shaft.
IMO, the primary advantage of the hotter flame is you can use smaller
tip and get the part you want hot faster before the rest heats up. W/ a
cooler flame it takes so long to heat conduction is carrying it away
where you don't want it as fast as you can warm it up...
Thanks all for your kind advice. As to the reverse thread,
I knew that was a possibility, but I can see threads so know it's
RH. Plus I have a new original parts bolt ready to go.
As for heating the motor shaft, I know that's the way
to go, but the visible part is very short and I feel I would
be heating other stuff that I didn't want to, especially to
get it hot enough to do any good. Guess I'm just a wimp..:)
As for heating the bolt itself (feel comfortable doing that),
why wouldn't that do SOME good? I'd reason that the bolt
would expand initially and compress the crap (rust from the
motor shaft), then after cooling the crap might not cause
it to bind as much. Myth or reality?
I will mull over everything you've all said. But when all
is said and done, looks like I will be putting my old Atlas
metal lathe to work!
Will keep y'all posted. Thanks again!
On Mon, 17 Jan 2005 04:52:08 GMT, frank1492
If you can't get heat to the shaft, try holding an ice cube to the head of
That might give you enough shrinkage.
Another approach is to rap the head the head of the bolt sharply with a
light hammer to free up any internal crap in the hole.
And of course there are various lubricants designed to seep in and loosen
And finally as I type this the thought comes to mind that there may be
something like Loctite to keep the bolt from backing out. If that is the
case heat will loosen it.
Heat with a torch, then spray it liberally with wd 40 while its good and
hot--on contraction / cooling, it will draw the vapor into the thread
interface.........this should not only break the bond, but also will turn
the "crud" into a sort of "grease", thus lubricating the threads.
Thanks all for your really wonderful ideas. I am saving all
of them for future reference.
The stainless bolt was threaded into the end of a very
old dishwasher motor. The washer is at least 20 years old,
and although Sears still has the parts, I wanted to avoid
buying a new motor. I am afraid the idea of having to do
a really good job of drilling (esp. through stainless) to get
a perfect job was a bit too scary for me, in the event
your remedies should fail.
Here's what I did. The bolt was used to hold two
impellers, with fairly heavy plastic hubs. So I threaded the
stub, got a piece of brass, went to my old Atlas metal lathe,
and made a small "cap" bolt with internal threads that I screwed
onto the stub. (What's the correct term for this item? Anybody
know?) I then drilled the impeller holes slightly larger to fit
around the internally threaded "cap". (Could do this perfectly
as the impellers could be chucked in the lathe.) Sawed a
slot in the end of the cap for tightening.
This all took a couple of hours, but it came out very well
and my blood pressure was kept in check.
BTW all bolts have been well-coated with Permatex 2
before insertion this time.
I feel a bit guilty that you guys spent so much time with
your great suggestions, then I end up using none of them.
I just didn't want to take any chances!
I'm sure many others will profit from your great ideas.
Chuckle- you sound like my brother, who also keeps an old lathe out in the
garage. He'll spend hours making a part, just to see if he can, before he
will buy one. Hey, it's cheaper than a shrink, and probably better therapy.
Actually, we did help. By taking the time to post the problem, read the
replies consider the options, you came up with a good solution. What is
important is that it works. You did not rush and screw things up.
Sounds like a case of stainless galling, perhaps. SS is notorious for
that if overtorqued w/o a lube.
Others have suggested I can only support directed heat at the shaft
around the bolt shaft, assuming you can get to it. Alternatively, you
<might> try putting the whole thing in the deep freeze overnight and see
if the differential thermal expansion will help. Applying heat while
cold may help, but you'll need more than propane to do any good, I
suspect. The cat's meow would have been to use an impact driver while
you still had the head, but that's over with now... :(
I fear that heating the bolt of shaft may ruin the motor as the heat
transfers to other parts. I would suggest getting a few left hand drill
bits. Yes they do make them. Try to drill the bolt out with them starting
with a small bit and increasing to a larger one as you go. Try to start in
the center. I have had great luck using a left handed bit. Most times the
bit will grab and unscrew the offending bolt for you. In cases when it does
not (this is where starting in the center sure helps) I drill to the point
where I have a very thin amount of bolt material left and use a punch to
bend the bolt inward and pull it out. Running a tap as a final step to clean
up the threads.
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