I am curious, is it best to heat the bolt head itself or around the
bolt? Will Heating the bolt heat make it more prone to snapping off?

It seems heating a bolt would make it expand, making it tighter?

By the way on all the other bolts I removed there was no rust.

I tend to heat the bolt.

As far as I understand, bolts secure by clamping force and
that causes stretching along the length.

So if you heat the bolt, it becomes longer and the clamping force is
reduced.

So it's easier to remove.


DOC


"Don" wrote in message
m...
I am curious, is it best to heat the bolt head itself or around the
bolt? Will Heating the bolt heat make it more prone to snapping off?

It seems heating a bolt would make it expand, making it tighter?

By the way on all the other bolts I removed there was no rust.

Don wrote:
I am curious, is it best to heat the bolt head itself or around the
bolt? Will Heating the bolt heat make it more prone to snapping off?

It seems heating a bolt would make it expand, making it tighter?

By the way on all the other bolts I removed there was no rust.

I was tought that it's the differential expansion across the bolt/block
interface which cracks the rust. ("Block" being the thing the bolt's
screwed into.")

Jeff

--
Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"My luck is so bad that if I bought a cemetery, people would stop dying."

"Jeff Wisnia" wrote: I was tought that it's the differential expansion
across the bolt/block interface which cracks the rust.
^^^^^^^^^^^^^
It is true that differential expansion could either make the bolt tighter or
looser, depending on the distribution of heat, but I don't think that is
what's working here. Hot rust is simply not as tough as cold rust. I would
heat the whole area, but concentrate the flame mainly on the bolt head.
That is the easiest place to apply the heat, which will then be conducted
down the bolt to the threads. If you tried to heat the "block" without
heating the bolt, I think you would have a hard time keeping the flame off
the bolt anyway. And, after you have applied enough heat to do some good,
conduction will probably result in a fairly even temperature distribution
across the thread interface.

The main object is to get it hot enough to weaken the bond, without getting
the steel so hot that you weaken it.

(Don) wrote in message om...
I am curious, is it best to heat the bolt head itself or around the
bolt? Will Heating the bolt heat make it more prone to snapping off?

It seems heating a bolt would make it expand, making it tighter?

By the way on all the other bolts I removed there was no rust.

No big loss if you change the temper of the bolt or distort it.
Same can't be said for whatever assembly it is froze into.

"Leo Lichtman" wrote in message
...

"Jeff Wisnia" wrote: I was tought that it's the differential expansion
across the bolt/block interface which cracks the rust.
^^^^^^^^^^^^^
It is true that differential expansion could either make the bolt tighter
or
looser, depending on the distribution of heat, but I don't think that is
what's working here. Hot rust is simply not as tough as cold rust. I
would
heat the whole area, but concentrate the flame mainly on the bolt head.
That is the easiest place to apply the heat, which will then be conducted
down the bolt to the threads. If you tried to heat the "block" without
heating the bolt, I think you would have a hard time keeping the flame off
the bolt anyway. And, after you have applied enough heat to do some good,
conduction will probably result in a fairly even temperature distribution
across the thread interface.

The main object is to get it hot enough to weaken the bond, without
getting
the steel so hot that you weaken it.



Get it nice and hot, then spray the crap out of it with WD40 ( Shut off you
torch first )

The rapid cooling and vaporization will draw the gaseous form of the
lubricant into the interface on contraction and break the oxide into
smaller, dislodged particles.

I keep wondering if he is dealing with a left hand thread, thus complicating
the issue for him.

--

SVL

PrecisionMachinisT wrote:
snip
I keep wondering if he is dealing with a left hand thread, thus complicating
the issue for him.

He said he got the other bolts off.
Having one bolt of a set LH would add comedy value though.

(Don)

I am curious, is it best to heat the bolt head itself or around the
bolt? Will Heating the bolt heat make it more prone to snapping off?

It seems heating a bolt would make it expand, making it tighter?

By the way on all the other bolts I removed there was no rust.

I don't know the answer, but I think heating the "whole thing (mostly bolt) is
a good expedient to try--hoping that "after" cooling there is some loosening.

In a simpler situation, if you have a steel pin (no threads) stuck in a bore,
if you heat the piece in which the dowel is stuck it will cause the surrounding
metal to expand, so the bore gets bigger. So in this situation, heat the
piece, not the pin. And, pull the pin while you're still hot.

I don't think this applies directly to the stuck-bolt situation, though.
Frank Morrison

"PrecisionMachinisT" wrote: (clip) I keep wondering if he is dealing with a
left hand thread, thus complicating the issue for him.
^^^^^^^^^^
He got all the other bolts out, so that is doubtful.

"Leo Lichtman" wrote in message
...

"PrecisionMachinisT" wrote: (clip) I keep wondering if he is dealing with
a
left hand thread, thus complicating the issue for him.
^^^^^^^^^^
He got all the other bolts out, so that is doubtful.



Okay, you got me---I dont read this group regularly.........

Generally, Im at alt.machines.cnc--I come here sometimes out of desperation,
else inadvertantly due to a certain prolific crossposter.

See ya....

Dont forget the wd40 trick, while it might not be quite the ticket in this
case, it really does work good in a lotta cases.

--

SVL

On 10 Mar 2004 02:56:28 GMT, (Fdmorrison) wrote:

(Don)

I am curious, is it best to heat the bolt head itself or around the
bolt? Will Heating the bolt heat make it more prone to snapping off?

It seems heating a bolt would make it expand, making it tighter?

By the way on all the other bolts I removed there was no rust.

I don't know the answer, but I think heating the "whole thing (mostly bolt) is
a good expedient to try--hoping that "after" cooling there is some loosening.

In a simpler situation, if you have a steel pin (no threads) stuck in a bore,
if you heat the piece in which the dowel is stuck it will cause the surrounding
metal to expand, so the bore gets bigger. So in this situation, heat the
piece, not the pin. And, pull the pin while you're still hot.

I don't think this applies directly to the stuck-bolt situation, though.
Frank Morrison
The theory is you want to break the rust structure. To do this, one
part needs to expand faster or more than the other. It is easier to
heat up the bolt than to heat the whole hole. Also, by heating and
expanding the bolt, when it cools it shrinks. Heat also helps any
penetrant penetrate.
WD 40 is a POOR lubricant and is not particularly effective on siezed
bolts. A 50 50 mix of Automatic trans fluid and laquer thinners does
a great job. Kroil, an old rust remedy, is basically just that.

PrecisionMachinisT wrote:

Get it nice and hot, then spray the crap out of it with WD40

WD-40 will only create a cloud of smoke and waste time and heat. Heat
the bolthead to near glowing and then apply beeswax to the joint.

Keep adding beeswax until it has had time to soak down the length of the
bolt, while still hot, turn in the direction to tighten bolt before
attempting to loosen it. Remove bolt.
Rick

Coupla reasons.

Rust between bolt and block offers thermal resistance so heat transfer
from bolt to block is limited. That's good: the bolt is disposable,
don't care what we do to the bolt with heat.

Rust is a surprisingly good insulator. If you doubt that, watch the
guys at Midas cut a longitudinal slit in an exhaust pipe or muffler
with a torch, without harming the inside pipe at all.

You can get the bolt very hot without heating the block much at all,
if you use a concentrated heat source as O/A or an arc.

Expansion of the bolt in the hole will both crush and shear some of
the weaker rust. When it cools there'll be more clearance -- Kroil
may go where it wouldn't go before.




On 9 Mar 2004 05:35:02 -0800, (Don) wrote:

I am curious, is it best to heat the bolt head itself or around the
bolt? Will Heating the bolt heat make it more prone to snapping off?

It seems heating a bolt would make it expand, making it tighter?

By the way on all the other bolts I removed there was no rust.

Kroil really does work if anything will, so that is a very useful
bit of info. Thanks!

On Wed, 10 Mar 2004 04:15:31 GMT, clare @ snyder.on .ca wrote:

. A 50 50 mix of Automatic trans fluid and laquer thinners does
a great job. Kroil, an old rust remedy, is basically just that.

I am a big fan of 50/50 atf/lt! The last instance was a
bearing on a de-barker head seized on the shaft.
Shaft is 2.188 dia and the inner race is 3" long. In
24 hours the 50/50 had penetrated 100% through!
Phil Kangas
--
Try to remove the yooper in me to reply.


Don Foreman wrote in message ...
Kroil really does work if anything will, so that is a
very useful
bit of info. Thanks!

On Wed, 10 Mar 2004 04:15:31 GMT, clare @ snyder.on .ca
wrote:

. A 50 50 mix of Automatic trans fluid and laquer
thinners does
a great job. Kroil, an old rust remedy, is basically just
that.

I had occasion to meet the President of CRC, I mentioned Kroil and the guy took
a mini snap. He that everbody says Kroil was better, when he calmed down a
little he said that CRC had tried to buy Kroil and Kroil would not sell.

My experience as a mechanic in the shipyards was that Kroil was better, and
that when you were using a smoke wrench to heat fasteners for easier removal
you had better success with nuts by heating only one flat of the nut. Heating
and cooling cycles seemed to work best.
Steam turbine casing flanges used a bolt with a hole in it for a heater. You
heated the fastener then torqued it to a certain value, when the fastener
cooled it got really tight. The exact temps escape me.

John H.

"Mustmaker" wrote: (snip) Steam turbine casing flanges used a bolt with a
hole in it for a heater. You heated the fastener then torqued it to a
certain value, when the fastener cooled it got really tight. (snip)
^^^^^^^^^^^
Now, THAT'S an interesting and little-known fact. I suppose, by wearing
leather gloves, and preheating bolts, could get them really tight.

"Rick" wrote in message
ink.net...
PrecisionMachinisT wrote:

Get it nice and hot, then spray the crap out of it with WD40

WD-40 will only create a cloud of smoke and waste time and heat. Heat
the bolthead to near glowing and then apply beeswax to the joint.


Dont tell me something I been doing for over 20 years dont work, Ive used
the method WAY too many times.

If WD40 wont penetrate the joint in a gaseous state, what makes you think
hot beeswax is gonna ?

--

SVL

PrecisionMachinisT wrote:

Dont tell me something I been doing for over 20 years dont work, Ive used
the method WAY too many times.

If WD40 wont penetrate the joint in a gaseous state, what makes you think
hot beeswax is gonna ?

More than 20 years working on marine steam and diesel plants where the
joints are exposed to temps near 900F when hot and moisture when cool.

There are many versions of mechanic-in-a-can and nothing, absolutely
nothing, works better than beeswax. It does not flash off and penetrates
far better than the extremely light oils used in household miracle
products.

Rick

On 9 Mar 2004 05:35:02 -0800, (Don) vaguely
proposed a theory
.......and in reply I say!:
remove ns from my header address to reply via email

(1) So you don't **** up what the bolt's sitting in.

(2) When you heat the bolt, you send the heat down the bolt. This
causes it to expand, and then it shrinks as it cools, loosening the
binding. Also, expansion and contraction can be very local. Heat the
bolt and it supplies heat to a very thin layer around it (or sheer
physical force causes expansion of its surroundings and cracks the
binding). This is enough.

(3) It's what everyone says to do G

I am curious, is it best to heat the bolt head itself or around the
bolt?
Will Heating the bolt heat make it more prone to snapping off?

yes. But the gains are usually greater than the losses.


It seems heating a bolt would make it expand, making it tighter?

By the way on all the other bolts I removed there was no rust.

************************************************** ** sorry

..........no I'm not!
remove ns from my header address to reply via email

Does Bill Gates dream of electronic sheep?

(2) When you heat the bolt, you send the heat down the bolt. This
causes it to expand, and then it shrinks as it cools, loosening the
binding. Also, expansion and contraction can be very local.

That's what I do on outboard motors with alum blocks etc. Very difficult to
drill a stainless bolt stub out of an alum block (. I then let the bolt cool
and before attempting to remove it, heat the area around it to expand it. Then
I try the bolt. Usually works on the first or second try.
Greg Sefton

On 12 Mar 2004 13:49:58 GMT, (Bray Haven) vaguely
proposed a theory
.......and in reply I say!:
remove ns from my header address to reply via email


That's what I do on outboard motors with alum blocks etc. Very difficult to
drill a stainless bolt stub out of an alum block (.

Not something I have tried, or look forward to with any pleasure.

I then let the bolt cool
and before attempting to remove it, heat the area around it to expand it. Then
I try the bolt. Usually works on the first or second try.

I guess with Auminium, "warm" would be more appropriate than "heat"
G. But yes, heating the surroundings a bit does help.


Greg Sefton

************************************************** ** sorry

..........no I'm not!
remove ns from my header address to reply via email

Does Bill Gates dream of electronic sheep?