Upper limit of heating hardened steel ?

[jcfx]

I'm trying to get a spanner nut off to service a Emco 4 speed mill quill bearings
there are two face pin style spanner nuts the larger one came off relatively easy, the inner one
is being difficult, I want to try heating the area to get some expansion and contraction
going in hopes of loosening the nut.

What would be the upper limit before I start to change the temper of the steel ?

[scmods]

Just a couple of things from my experiences.

First, taking things apart with heat is not the same thing as assembling a shrink fit. It is difficult to heat the outside part without heating the inside too.

I assume that this is not a corrosion issue that requires near red heat to break the corrosion, probably ruining your parts, so let's examine alternatives. Depending on the style of bearing employed in the spindle, I would suspect that the assembly employs shims to control preload/clearance (none) and is probably tightened against that.

Given this probability, if this were mine, I'd modify a deep socket (small hand grinder) to fit the pin holes in the spanner nut and then use a hand impacter or, if unavailable, an air impacter to jar the nut loose. You'll probably not use the socket again, but it beats ruining the spindle.

Be sure to post what eventually works.

Good Luck

Bill Walck

[jcfx]

Hi Bill,

I've jigged up a heat gun and candy thermometer to make sure that I'm not heating past a certain point ( 200º F )
like I do for installing bearings like you said it's impossible to heat the part you want to remove without
heating the surrounding area...back to square one !

It's not a corrosion issue, but it might be right hand thread vs a left hand thread issue, tho I did try it both ways using a
home made face pin spanner, I do have some real adjustable face spanners on order so I'll probably give those a try
when they arrive.

I didn't think that deep sockets would work since part of the spindle protrudes up about 3.625" from the spanner nut,
but looking around there does seem to be sockets deep enough to go over the protrusion, if the square drive end is 1".
I'll give that try if the spanner wrenches fail.

[rudd]

I am not advocating for or against the use of heat in this case, personally, I wouldn't from what I understand of the problem. I'd not be as worried about changing the temper of the spindle as I would be about cooking the bearings.
I'd like to say though, trying to heat something up with a heat gun, of course the two parts are going to stay about even in temp. Wide, low temp heat. What you would want is very hot, very narrow source to raise the temp. of the the desired part very quickly. Not knowing the relative masses of the two parts, you could use say a oxy-acytelene cutting tip - with out hitting the cutting valve lever - to change the temp of the nut in relation to the spindle - but you'd have to work fast before the heat flowed into the spindle. If the spindle was massive enough, the spindle might not actually get that hot. You might put in as many total BTU's as the heat gun, but you'd heat a much smaller mass of metal to a higher temp.
I've had to learn the finer points of thermal persuasion over the years - old steam locomotives, hundred year old machinery in seacost locations etc.
Consider getting a frozen nut off a stud - with the cutting head, you can get the nut orange and the stud will still be black so it doesn't wring off. With a rosebud - same high temp, but broader flame - you'd get both parts equally as hot, probably would not loosen the nut, and would probably twist off the heated stud.
On something like a frozen washout plug - bronze plug in a steel sheet, you heat the plug, not the sheet, let it cool. It tried to expand, the steel would not let it, when it cools it is a tiny bit smaller and may come out with your hand.
In our next installment, we'll practice washing nuts off of studs without damaging the threads..

[jcfx]

The bearings in the spindle were gritty feeling to begin with, worse now that I've given it a few soakings with
PB Blaster, but the whole exercise was to replace them anyway.
Not sure that oxy-acetylene torch would work in this case unless I got a jewelers micro size torch,
the spanner nut is just 1.18" in dia. One idea I've been toying with is to keep the the spindle cool by
filling the spindle area where the nut is with ice pack gel, freezing it, then heating the nut with
a small butane torch.

[CaptonZap]

To answer your question, most heat treated steels are tempered after being hardened. (Files may be an exception) The tempering temperatures vary, depending on how much the hardness is to be reduced. Tempering temperatures range from 200 deg F to 1000 deg F.
My usual method is to cover the piece with an oil coating, and heat until the oil smokes, which is around 450 deg F, +/-.
That equates to a pale yellow. If it gets to a blue color, it is 625 deg,+/-.

CZ

[liveaboard]

Having removed many a frozen nut, my opinion is that heat does very little unless you use a lot of it; like the part starts to glow at least a little bit.
In this case, that would very likely do a lot of damage, so heat is not going to be your friend on this.
A butane torch won't get it hot enough.
Make a tool that will let you get an impact tool onto it; a thingy with a 1/2" square drive for a socket, that you strike with a hammer to apply simultaneous shock and torque. scmods idea of grinding a socket would give you something with the right characteristics. You might need to weld a short pipe section to that to clear the spindle.
If that won't work, then desperate measures may be required; like welding a lever to the nut for instance. That will also heat the nut rapidly and fairly locally.

[jcfx]

All the while I was thinking it must have tightened itself to a cold weld after 40 odd years
since it's a left hand thread and the arbor that the spanner nut was on rotated clockwise when under
power. All my attempts at getting it off failed, and either the home made wrench or store bought
would cam out at one point, because I couldn't keep the wrench parallel enough as I was yanking on it.
A $ 6 clamp on shaft collar and a $ 15 adjustable face spanner wrench did it, although I'm
certain the home made one would have worked, the clamp on shaft collar kept the spanner wrench
parallel, came off with barely a grunt.

[Happycamper]

Use Kroiloil. Soak it liberally several times then let it sit. If it doesn't come loose, I'd be surprised. Kroiloil is a penetrating oil and I do mean penetrating.

[SteveM]

Use Kroiloil. Soak it liberally several times then let it sit. If it doesn't come loose, I'd be surprised. Kroiloil is a penetrating oil and I do mean penetrating.

My can of Kroil says that it creeps, and it really does.

Another good thing to use is a 50/50 mix of ATF and acetone. The ATF does the work and the acetone thins it so that it can creep in.

One magazine tested penetrants and Kroil came in second to ATF/acetone.

I keep a bottle of it on hand already mixed.

Steve

[wlw-19958]

Hi There,

Use Kroiloil. Soak it liberally several times then let it sit. If it doesn't come loose, I'd be surprised. Kroiloil is a penetrating oil and I do mean penetrating.

My can of Kroil says that it creeps, and it really does.

Another good thing to use is a 50/50 mix of ATF and acetone. The ATF does the work and the acetone thins it so that it can creep in.

One magazine tested penetrants and Kroil came in second to ATF/acetone.

I keep a bottle of it on hand already mixed.

Steve

This may be true but Acetone will eat painted surfaces and many plastics.
I've never had Kroil damage paint or plastics so, be aware of the surrounding
area when using ATF/Acetone.

Good Luck!
-Blue Chips-
Webb

[JackF]

I think his last post says he got it off.


Jack.