I've got a little project I am working on. Steel shaft in steel hole. At
first I was just going to bore close, and skim cut the bore until the shaft
just barely fit then secure it with a set screw. Some strength against
twisting is important. Then I was wondering if I might get a better
concentricity by heating the part, and letting it cool around the shaft.
Still with a flat on the shaft and a set screw just to be safe.

The part with the hole has an outside diameter where the hole is of about
1.00". The hole is 0.500" apx. Final cut dimension of the hole will be
determined by trying to figure out how much to heat the part and how much
expansion I can get. The shaft is hardened tool steel with a diameter of
0.4995" apx. The part is 1018. My thought was to bore to .49 then ream to
..499 with an under reamer. Heat the part, insert the shaft, snug up set
screw momentarily to align the flat, and allow part to cool. Then tighten
set screw. This is to be a modestly accurate permanent installation.

How much heat do I need on the part? I think I'll need a little more growth
than necessary to fit due to rapid cooling while assembling, and the slow
clumsiness of working with heat heat resistant gloves on and/or using tongs.
Ambient in my shop is around 70F in the afternoon lately.

Please lets not go off on tangents. Thanks for any help or suggestions.






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On 1/15/2014 9:21 AM, Bob La Londe wrote:
I've got a little project I am working on. Steel shaft in steel hole.
At first I was just going to bore close, and skim cut the bore until the
shaft just barely fit then secure it with a set screw. Some strength
against twisting is important. Then I was wondering if I might get a
better concentricity by heating the part, and letting it cool around the
shaft. Still with a flat on the shaft and a set screw just to be safe.

The part with the hole has an outside diameter where the hole is of
about 1.00". The hole is 0.500" apx. Final cut dimension of the hole
will be determined by trying to figure out how much to heat the part and
how much expansion I can get. The shaft is hardened tool steel with a
diameter of 0.4995" apx. The part is 1018. My thought was to bore to
.49 then ream to .499 with an under reamer. Heat the part, insert the
shaft, snug up set screw momentarily to align the flat, and allow part
to cool. Then tighten set screw. This is to be a modestly accurate
permanent installation.

How much heat do I need on the part? I think I'll need a little more
growth than necessary to fit due to rapid cooling while assembling, and
the slow clumsiness of working with heat heat resistant gloves on and/or
using tongs. Ambient in my shop is around 70F in the afternoon lately.

Please lets not go off on tangents. Thanks for any help or suggestions.






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If your intent is perfect concentricity, isn't a flat the last thing you
want to do?

"mike" wrote in message
...
On 1/15/2014 9:21 AM, Bob La Londe wrote:
I've got a little project I am working on. Steel shaft in steel hole.
At first I was just going to bore close, and skim cut the bore until the
shaft just barely fit then secure it with a set screw. Some strength
against twisting is important. Then I was wondering if I might get a
better concentricity by heating the part, and letting it cool around the
shaft. Still with a flat on the shaft and a set screw just to be safe.

The part with the hole has an outside diameter where the hole is of
about 1.00". The hole is 0.500" apx. Final cut dimension of the hole
will be determined by trying to figure out how much to heat the part and
how much expansion I can get. The shaft is hardened tool steel with a
diameter of 0.4995" apx. The part is 1018. My thought was to bore to
.49 then ream to .499 with an under reamer. Heat the part, insert the
shaft, snug up set screw momentarily to align the flat, and allow part
to cool. Then tighten set screw. This is to be a modestly accurate
permanent installation.

How much heat do I need on the part? I think I'll need a little more
growth than necessary to fit due to rapid cooling while assembling, and
the slow clumsiness of working with heat heat resistant gloves on and/or
using tongs. Ambient in my shop is around 70F in the afternoon lately.

Please lets not go off on tangents. Thanks for any help or suggestions.






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TANGENT ALERT:

If your intent is perfect concentricity, isn't a flat the last thing you
want to do?

Response to tangent:
A small flat, not the full wall length of the engagement. The flat is to
provide purchase for a set screw to prevent any "reasonable" chance of
twisting like the tiny set screw size flat on the side of an end mill.
There would be full circular engagement above and below the tiny little
flat.



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"Bob La Londe" wrote in message
...
"mike" wrote in message
...
On 1/15/2014 9:21 AM, Bob La Londe wrote:
I've got a little project I am working on. Steel shaft in steel hole.
At first I was just going to bore close, and skim cut the bore until the
shaft just barely fit then secure it with a set screw. Some strength
against twisting is important. Then I was wondering if I might get a
better concentricity by heating the part, and letting it cool around the
shaft. Still with a flat on the shaft and a set screw just to be safe.

The part with the hole has an outside diameter where the hole is of
about 1.00". The hole is 0.500" apx. Final cut dimension of the hole
will be determined by trying to figure out how much to heat the part and
how much expansion I can get. The shaft is hardened tool steel with a
diameter of 0.4995" apx. The part is 1018. My thought was to bore to
.49 then ream to .499 with an under reamer. Heat the part, insert the
shaft, snug up set screw momentarily to align the flat, and allow part
to cool. Then tighten set screw. This is to be a modestly accurate
permanent installation.

How much heat do I need on the part? I think I'll need a little more
growth than necessary to fit due to rapid cooling while assembling, and
the slow clumsiness of working with heat heat resistant gloves on and/or
using tongs. Ambient in my shop is around 70F in the afternoon lately.

Please lets not go off on tangents. Thanks for any help or suggestions.






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TANGENT ALERT:

If your intent is perfect concentricity, isn't a flat the last thing you
want to do?

Response to tangent:
A small flat, not the full wall length of the engagement. The flat is to
provide purchase for a set screw to prevent any "reasonable" chance of
twisting like the tiny set screw size flat on the side of an end mill.
There would be full circular engagement above and below the tiny little
flat.


A quick search shows that generically the coefficient of expansion "steel"
is about 0.0000072 inches per inch per degree F. So figuring worst case at
..500 and figuring I need .002-.003 clearance to be able to finish the
project before it cools and seizes up I should figure on needing .004
expansion per .5 inches.

..0000072*.5=.0000036.

..004/.0000036= 1111.11 degrees. This doesn't sound practical for the tools
I have on hand for my application.

..003/.0000036=833.33 degrees. Maybe doable, but uncomfortabley close. Time
may be an issue.

..002/.0000036=555.55 degrees. Certainly within the ability to reach
temperature, but tolerance will be close during fit up, and time may be to
short to complete fit up. Because of the close tolerance the shaft may
rapidly cool the part.

TANGENT THOUGHT. The amount of energy required to get the growth to make
the fit up suggests that the set screw may be totally superfluous.

Back on topic... a sample part and shaft to test with may be a wise
investment of time. Something cut with hexes so it can be clamped up and
torque of the joint / joint slip tested afterwards.








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On Wednesday, January 15, 2014 12:21:42 PM UTC-5, Bob La Londe wrote:
I've got a little project I am working on. Steel shaft in steel hole. At

first I was just going to bore close, and skim cut the bore until the shaft

just barely fit then secure it with a set screw. Some strength against

twisting is important. Then I was wondering if I might get a better

concentricity by heating the part, and letting it cool around the shaft.

Still with a flat on the shaft and a set screw just to be safe.



The part with the hole has an outside diameter where the hole is of about

1.00". The hole is 0.500" apx. Final cut dimension of the hole will be

determined by trying to figure out how much to heat the part and how much

expansion I can get. The shaft is hardened tool steel with a diameter of

0.4995" apx. The part is 1018. My thought was to bore to .49 then ream to

.499 with an under reamer. Heat the part, insert the shaft, snug up set

screw momentarily to align the flat, and allow part to cool. Then tighten

set screw. This is to be a modestly accurate permanent installation.



How much heat do I need on the part? I think I'll need a little more growth

than necessary to fit due to rapid cooling while assembling, and the slow

clumsiness of working with heat heat resistant gloves on and/or using tongs.

Ambient in my shop is around 70F in the afternoon lately.



Please lets not go off on tangents. Thanks for any help or suggestions.













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IIRC, shrink fits are generally .003" for the first inch of diameter, .001" per inch larger.

So, you might bore your 1-inch part's hole .4965" for your .4995" shafting.

Slowly and evenly heat the part with the hole to a dullish red. Don't let it develop any scale.

Insert the cool shaft in one swift motion, you won't have time to mess with your set screw alignment.
The shaft instantly starts to expand with the heat, further motion will not likely be an option.

Then cool it all off with water.

Your set screw will probably be redundant.

Good luck.

--
PaulS

"PCS" wrote in message
...
On Wednesday, January 15, 2014 12:21:42 PM UTC-5, Bob La Londe wrote:
I've got a little project I am working on. Steel shaft in steel hole.
At

first I was just going to bore close, and skim cut the bore until the
shaft

just barely fit then secure it with a set screw. Some strength against

twisting is important. Then I was wondering if I might get a better

concentricity by heating the part, and letting it cool around the shaft.

Still with a flat on the shaft and a set screw just to be safe.



The part with the hole has an outside diameter where the hole is of about

1.00". The hole is 0.500" apx. Final cut dimension of the hole will be

determined by trying to figure out how much to heat the part and how much

expansion I can get. The shaft is hardened tool steel with a diameter of

0.4995" apx. The part is 1018. My thought was to bore to .49 then ream
to

.499 with an under reamer. Heat the part, insert the shaft, snug up set

screw momentarily to align the flat, and allow part to cool. Then
tighten

set screw. This is to be a modestly accurate permanent installation.



How much heat do I need on the part? I think I'll need a little more
growth

than necessary to fit due to rapid cooling while assembling, and the slow

clumsiness of working with heat heat resistant gloves on and/or using
tongs.

Ambient in my shop is around 70F in the afternoon lately.



Please lets not go off on tangents. Thanks for any help or suggestions.













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IIRC, shrink fits are generally .003" for the first inch of diameter,
.001" per inch larger.

So, you might bore your 1-inch part's hole .4965" for your .4995"
shafting.

Slowly and evenly heat the part with the hole to a dullish red. Don't let
it develop any scale.

Insert the cool shaft in one swift motion, you won't have time to mess
with your set screw alignment.
The shaft instantly starts to expand with the heat, further motion will
not likely be an option.

Then cool it all off with water.

Your set screw will probably be redundant.

Good luck.


Paul, Thanks. I did a little research and a little math in one of the other
posts. I did not know the guideline for size difference, but I did
calculate that it takes quite a lot of energy to expand the metal
sufficiently to get a fit up, and guessed that the screw might not be
needed.






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"Bob La Londe" wrote in message
...
"PCS" wrote in message
...
On Wednesday, January 15, 2014 12:21:42 PM UTC-5, Bob La Londe wrote:
I've got a little project I am working on. Steel shaft in steel hole.
At

first I was just going to bore close, and skim cut the bore until the
shaft

just barely fit then secure it with a set screw. Some strength against

twisting is important. Then I was wondering if I might get a better

concentricity by heating the part, and letting it cool around the shaft.

Still with a flat on the shaft and a set screw just to be safe.



The part with the hole has an outside diameter where the hole is of
about

1.00". The hole is 0.500" apx. Final cut dimension of the hole will be

determined by trying to figure out how much to heat the part and how
much

expansion I can get. The shaft is hardened tool steel with a diameter
of

0.4995" apx. The part is 1018. My thought was to bore to .49 then ream
to

.499 with an under reamer. Heat the part, insert the shaft, snug up set

screw momentarily to align the flat, and allow part to cool. Then
tighten

set screw. This is to be a modestly accurate permanent installation.



How much heat do I need on the part? I think I'll need a little more
growth

than necessary to fit due to rapid cooling while assembling, and the
slow

clumsiness of working with heat heat resistant gloves on and/or using
tongs.

Ambient in my shop is around 70F in the afternoon lately.



Please lets not go off on tangents. Thanks for any help or suggestions.













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IIRC, shrink fits are generally .003" for the first inch of diameter,
.001" per inch larger.

So, you might bore your 1-inch part's hole .4965" for your .4995"
shafting.

Slowly and evenly heat the part with the hole to a dullish red. Don't
let it develop any scale.

Insert the cool shaft in one swift motion, you won't have time to mess
with your set screw alignment.
The shaft instantly starts to expand with the heat, further motion will
not likely be an option.

Then cool it all off with water.

Your set screw will probably be redundant.

Good luck.


Paul, Thanks. I did a little research and a little math in one of the
other posts. I did not know the guideline for size difference, but I did
calculate that it takes quite a lot of energy to expand the metal
sufficiently to get a fit up, and guessed that the screw might not be
needed.


My only real issue then is getting a good bore of .4965 with the tools I
have. Reaming to .499 would be easy, but I have to bore to any off size.




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On 1/15/2014 12:21, Bob La Londe wrote:
I've got a little project I am working on. Steel shaft in steel hole.
At first I was just going to bore close, and skim cut the bore until the
shaft just barely fit then secure it with a set screw. Some strength
against twisting is important. Then I was wondering if I might get a
better concentricity by heating the part, and letting it cool around the
shaft. Still with a flat on the shaft and a set screw just to be safe.

The part with the hole has an outside diameter where the hole is of
about 1.00". The hole is 0.500" apx. Final cut dimension of the hole
will be determined by trying to figure out how much to heat the part and
how much expansion I can get. The shaft is hardened tool steel with a
diameter of 0.4995" apx. The part is 1018. My thought was to bore to
.49 then ream to .499 with an under reamer. Heat the part, insert the
shaft, snug up set screw momentarily to align the flat, and allow part
to cool. Then tighten set screw. This is to be a modestly accurate
permanent installation.

How much heat do I need on the part? I think I'll need a little more
growth than necessary to fit due to rapid cooling while assembling, and
the slow clumsiness of working with heat heat resistant gloves on and/or
using tongs. Ambient in my shop is around 70F in the afternoon lately.

Please lets not go off on tangents. Thanks for any help or suggestions.






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Let's see. Steel coefficient of expansion is .0000072" per inch per
degree Fahrenheit above ambient. Later post says .003 needed.
..003/.0000072=416 degrees. Bore is .5 inch, so double that, 832 degrees.
Plus 70 degrees ambient, about 900 degrees. Clean part so no oil scales
up in bore. Heat slowly, probably on a fire brick, so it doesn't lose
heat so fast when removing flame. Squeeze bottle with water will cool it
down fast, without shocking it.

--
Steve Walker
(remove brain when replying)

Bob La Londe wrote:
I've got a little project I am working on. Steel shaft in steel hole. At
first I was just going to bore close, and skim cut the bore until the shaft
just barely fit then secure it with a set screw. Some strength against
twisting is important. Then I was wondering if I might get a better
concentricity by heating the part, and letting it cool around the shaft.
Still with a flat on the shaft and a set screw just to be safe.

The part with the hole has an outside diameter where the hole is of about
1.00". The hole is 0.500" apx. Final cut dimension of the hole will be
determined by trying to figure out how much to heat the part and how much
expansion I can get. The shaft is hardened tool steel with a diameter of
0.4995" apx. The part is 1018. My thought was to bore to .49 then ream to
.499 with an under reamer. Heat the part, insert the shaft, snug up set
screw momentarily to align the flat, and allow part to cool. Then tighten
set screw. This is to be a modestly accurate permanent installation.

How much heat do I need on the part? I think I'll need a little more growth
than necessary to fit due to rapid cooling while assembling, and the slow
clumsiness of working with heat heat resistant gloves on and/or using tongs.
Ambient in my shop is around 70F in the afternoon lately.

Please lets not go off on tangents. Thanks for any help or suggestions.


550-600 degrees will get you around .0025" of expansion. Then if
possible toss the shaft onto dry ice for 20 minutes. That will give you
..0005" more.

You are working with almost the same dimensions and materials as a
connecting rod with a pressed pin.

Watch your heating method, you want the heat even and slow to prevent
thermal distortion. Make sure the hole is perfectly clean and the shaft
is perfectly clean. Anything that causes a snag will screw you up. As a
twist inhibitor you could put striations on the area of the shaft where
the part will stop. Just make sure they are below the surface so they
don't inhibit the assembly. This is done on some pins that have oiling
provisions to prevent rotation.

In the case of the pins (which are hollow) you have around 5-6 seconds
before the parts are locked. With the solid shaft you might get a bit
more but I wouldn't count on it.

Do NOT use any forced cooling, let them air cool slowly. Any type of
quench will cause thermal distortion and probably thermal shock enough
to damage the part.


--
Steve W.

"Steve W."
Do NOT use any forced cooling, let them air cool
slowly. Any type of quench will cause thermal
distortion and probably thermal shock enough to
damage the part.


--
Steve W.

I agree with Steve. Don't shock it with a quench!
It's not needed...
pdk

"Bob La Londe" wrote in message
...

Back on topic... a sample part and shaft to test with may be a wise
investment of time. Something cut with hexes so it can be clamped
up and torque of the joint / joint slip tested afterwards.


If you are willing to experiment you could compare the hot fit to
pressing the parts together cold.
jsw

On Wed, 15 Jan 2014 10:21:42 -0700, "Bob La Londe"
wrote:

I've got a little project I am working on. Steel shaft in steel hole. At
first I was just going to bore close, and skim cut the bore until the shaft
just barely fit then secure it with a set screw. Some strength against
twisting is important. Then I was wondering if I might get a better
concentricity by heating the part, and letting it cool around the shaft.
Still with a flat on the shaft and a set screw just to be safe.

The part with the hole has an outside diameter where the hole is of about
1.00". The hole is 0.500" apx. Final cut dimension of the hole will be
determined by trying to figure out how much to heat the part and how much
expansion I can get. The shaft is hardened tool steel with a diameter of
0.4995" apx. The part is 1018. My thought was to bore to .49 then ream to
.499 with an under reamer. Heat the part, insert the shaft, snug up set
screw momentarily to align the flat, and allow part to cool. Then tighten
set screw. This is to be a modestly accurate permanent installation.

How much heat do I need on the part? I think I'll need a little more growth
than necessary to fit due to rapid cooling while assembling, and the slow
clumsiness of working with heat heat resistant gloves on and/or using tongs.
Ambient in my shop is around 70F in the afternoon lately.

Please lets not go off on tangents. Thanks for any help or suggestions.






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If I was doing your assembly I would heat the one part and freeze the
other just to get a little more clearance. Then I would carefully run
a drill inside the tapped hole to dimple the shaft. Finally, I would
install the setscrew. I think the screw would be redundant but it
won't hurt to put one in. And a cup point setscrew, or the type with
the cup point that's knurled, will locate well in the little dimple.
And the dimple will be perfectly aligned with the screw hole.
Eric

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On Wed, 15 Jan 2014 10:21:42 -0700, "Bob La Londe"
wrote:

I've got a little project I am working on. Steel shaft in steel hole. At
first I was just going to bore close, and skim cut the bore until the shaft
just barely fit then secure it with a set screw. Some strength against
twisting is important. Then I was wondering if I might get a better
concentricity by heating the part, and letting it cool around the shaft.
Still with a flat on the shaft and a set screw just to be safe.

The part with the hole has an outside diameter where the hole is of about
1.00". The hole is 0.500" apx. Final cut dimension of the hole will be
determined by trying to figure out how much to heat the part and how much
expansion I can get. The shaft is hardened tool steel with a diameter of
0.4995" apx. The part is 1018. My thought was to bore to .49 then ream to
.499 with an under reamer. Heat the part, insert the shaft, snug up set
screw momentarily to align the flat, and allow part to cool. Then tighten
set screw. This is to be a modestly accurate permanent installation.

How much heat do I need on the part? I think I'll need a little more growth
than necessary to fit due to rapid cooling while assembling, and the slow
clumsiness of working with heat heat resistant gloves on and/or using tongs.
Ambient in my shop is around 70F in the afternoon lately.

Please lets not go off on tangents. Thanks for any help or suggestions.






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Freeze the shaft and heat the part.
The coefficient of thermal expansion for steel is 0.00000645in/in/deg
F.
You have 1/2 inch to work with, so .000003225" per F degree temp
difference..
If you measure at 70F, and freeze the shaft to 0f and heat the part to
350F you have 420 degrees and .00135 inches of differential expansion.

On Wed, 15 Jan 2014 16:50:51 -0500, Steve Walker
wrote:

On 1/15/2014 12:21, Bob La Londe wrote:
I've got a little project I am working on. Steel shaft in steel hole.
At first I was just going to bore close, and skim cut the bore until the
shaft just barely fit then secure it with a set screw. Some strength
against twisting is important. Then I was wondering if I might get a
better concentricity by heating the part, and letting it cool around the
shaft. Still with a flat on the shaft and a set screw just to be safe.

The part with the hole has an outside diameter where the hole is of
about 1.00". The hole is 0.500" apx. Final cut dimension of the hole
will be determined by trying to figure out how much to heat the part and
how much expansion I can get. The shaft is hardened tool steel with a
diameter of 0.4995" apx. The part is 1018. My thought was to bore to
.49 then ream to .499 with an under reamer. Heat the part, insert the
shaft, snug up set screw momentarily to align the flat, and allow part
to cool. Then tighten set screw. This is to be a modestly accurate
permanent installation.

How much heat do I need on the part? I think I'll need a little more
growth than necessary to fit due to rapid cooling while assembling, and
the slow clumsiness of working with heat heat resistant gloves on and/or
using tongs. Ambient in my shop is around 70F in the afternoon lately.

Please lets not go off on tangents. Thanks for any help or suggestions.






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Let's see. Steel coefficient of expansion is .0000072" per inch per
degree Fahrenheit above ambient. Later post says .003 needed.
.003/.0000072=416 degrees. Bore is .5 inch, so double that, 832 degrees.
Plus 70 degrees ambient, about 900 degrees. Clean part so no oil scales
up in bore. Heat slowly, probably on a fire brick, so it doesn't lose
heat so fast when removing flame. Squeeze bottle with water will cool it
down fast, without shocking it.
For a small part like this I'd consider heating the collar on a
steel or copper block with a hole drilled in it for the shaft. Mabee a
recess to hold the collar, - hole oversized and drilled to required
depth to precision locate the shaft on insertion. How much load will
this part be under? I very much doubt you will require a 3 thou
interference fit for this installation. The block will hold heat to
keep the temperature of the collar up. The collar has less mass than
the shaft. Heat the collar and block - freeze the shaft, insert the
shaft and rap it into the hole with one good smack of a mallet and
"Bob's your mother's brother"

On Wed, 15 Jan 2014 10:21:42 -0700, "Bob La Londe"
wrote:

I've got a little project I am working on. Steel shaft in steel hole. At
first I was just going to bore close, and skim cut the bore until the shaft
just barely fit then secure it with a set screw. Some strength against
twisting is important. Then I was wondering if I might get a better
concentricity by heating the part, and letting it cool around the shaft.
Still with a flat on the shaft and a set screw just to be safe.

The part with the hole has an outside diameter where the hole is of about
1.00". The hole is 0.500" apx. Final cut dimension of the hole will be
determined by trying to figure out how much to heat the part and how much
expansion I can get. The shaft is hardened tool steel with a diameter of
0.4995" apx. The part is 1018. My thought was to bore to .49 then ream to
.499 with an under reamer. Heat the part, insert the shaft, snug up set
screw momentarily to align the flat, and allow part to cool. Then tighten
set screw. This is to be a modestly accurate permanent installation.

How much heat do I need on the part? I think I'll need a little more growth
than necessary to fit due to rapid cooling while assembling, and the slow
clumsiness of working with heat heat resistant gloves on and/or using tongs.
Ambient in my shop is around 70F in the afternoon lately.

Please lets not go off on tangents. Thanks for any help or suggestions.

snip
Don't know if this will be considered a tangent or not g.
Is a heated shrink fit a requirement??
Compleat the job as per the first three sentences above, then apply
some LockTite bearing retainer. That plus your set screw should
provide all the retention needed.
rgentryatozdotnet

On 2014-01-15, PCS wrote:
On Wednesday, January 15, 2014 12:21:42 PM UTC-5, Bob La Londe wrote:

I've got a little project I am working on. Steel shaft in steel hole. At
first I was just going to bore close, and skim cut the bore until the shaft
just barely fit then secure it with a set screw. Some strength against
twisting is important. Then I was wondering if I might get a better
concentricity by heating the part, and letting it cool around the shaft.
Still with a flat on the shaft and a set screw just to be safe.

[ ... ]

How much heat do I need on the part? I think I'll need a little more growth
than necessary to fit due to rapid cooling while assembling, and the slow
clumsiness of working with heat heat resistant gloves on and/or using tongs.
Ambient in my shop is around 70F in the afternoon lately.

[ ... ]

IIRC, shrink fits are generally .003" for the first inch of diameter,
.001" per inch larger.

So, you might bore your 1-inch part's hole .4965" for your .4995"
shafting.

Sounds reasonable.

Slowly and evenly heat the part with the hole to a dullish red. Don't
let it develop any scale.

Easiest to avoid if you can heat it in an inert atmosphere --
Nitrogen or Argon for example.

Insert the cool shaft in one swift motion, you won't have time to mess
with your set screw alignment. The shaft instantly starts to expand
with the heat, further motion will not likely be an option.

If you want a bit more clearance to work with, get some liquid
nitrogen, and *cool* the shaft while you heat the collar (or whatever
kind of part -- I'll use collar for simplicity). You can get the Liquid
Nitrogen from a welding gas supply place usually. Take a big thermos if
you don't have a Dewar made for the task. Ideally, one of the fragile
glass-lined thermos jars. If not that, several large styrofoam cups
nested, and handle with good gloves. Drive with the windows open so you
don't pass out from the nitrogen which boils off displacing the oxygen
in the car.

The Liquid Nitrogen is at 77 K (-231.07 F), so that will add a
bit more difference in size.

Can you place the collar on a support with a hole sized to pass
the shaft? If so, mount another ring above it a loose fit on the shaft
at room temperature, and a few inches above the collar. This will let
you drop the shaft in with a pretty good alignment, and the support will
be at the same temperature as the collar, so it will keep that warm a
few seconds longer. Set a stop below the support so the shaft goes the
right distance into the collar. Then heat the one, cool the other, drop
in and stand back.

Then cool it all off with water.

Your set screw will probably be redundant.

Agreed. That will be a serious interference fit. If it isn't,
the assembly can always be drilled for a taper pin to lock it.

Enjoy,
DoN.

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On 2014-01-15, Bob La Londe wrote:

[ ... ]

My only real issue then is getting a good bore of .4965 with the tools I
have. Reaming to .499 would be easy, but I have to bore to any off size.

Possibilities:

1) Adjustable reamer.

2) Lap to size.

3) Roller burnisher.

4) Roll up some emery paper and twist it in the bore. (How long is
the bore?

However, all three require a way to *precisely* measure the
bore. Nicest is one of the the tri-mikes of the right range. Lacking
that, a shaft with a minimal taper (e.g. 0.001/inch) and slide it in
until it stops. Mark at the edge of the hole with a felt-tip pen, pull
it out, and measure with a tenths-reading micrometer. (Likely more
repeatable than a small-hole gauge, which requires a really good feel.

Or -- perhaps set up a toolpost grinder on the lathe (with
proper protection for all sliding surfaces). Set the compound as close
as you can to 5.71 degrees (nearly parallel to the workpiece axis) and
this will allow you to move in 0.0001" for every 0.001" you turn on the
compound feed dial (assuming that the dial is direct reading -- *beware*
some compounds read half of actual motion so you know how much diameter
you will take off instead of how much radius). It makes more sense for
the cross-feed to be so calibrated, but sometimes it is also done on the
compound where it only makes sense when parallel to the cross-feed. :-)

Good Luck,
DoN.

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On Wednesday, January 15, 2014 12:21:42 PM UTC-5, Bob La Londe wrote:
Then I was wondering if I might get a better

concentricity by heating the part, and letting it cool around the shaft.

Still with a flat on the shaft and a set screw just to be safe.


Please lets not go off on tangents. Thanks for any help or suggestions.



You might consider this as going off on a tangent, but to get the best concentricity I would join the rough machined parts and then machine the part.

Dan

On 1/15/2014 12:50 PM, Bob La Londe wrote:
"mike" wrote in message




TANGENT ALERT:

If your intent is perfect concentricity, isn't a flat the last thing you
want to do?

Response to tangent:
A small flat, not the full wall length of the engagement. The flat is to
provide purchase for a set screw to prevent any "reasonable" chance of
twisting like the tiny set screw size flat on the side of an end mill.
There would be full circular engagement above and below the tiny little
flat.

It's all a matter of degree.
If your primary objective is concentricity, shouldn't any deviations
from circular be radially symmetrical both dimensionally and for
applied force/setscrews?

I suggest that setscrews work by deforming something elastic.

One man's tangent is another man's failure to consider the consequences.
Sometimes, the cure is worse than the disease.
It's all a matter of degree.

"mike" wrote in message
...
On 1/15/2014 12:50 PM, Bob La Londe wrote:
"mike" wrote in message




TANGENT ALERT:

If your intent is perfect concentricity, isn't a flat the last thing you
want to do?

Response to tangent:
A small flat, not the full wall length of the engagement. The flat is to
provide purchase for a set screw to prevent any "reasonable" chance of
twisting like the tiny set screw size flat on the side of an end mill.
There would be full circular engagement above and below the tiny little
flat.

It's all a matter of degree.
If your primary objective is concentricity, shouldn't any deviations
from circular be radially symmetrical both dimensionally and for
applied force/setscrews?

I suggest that setscrews work by deforming something elastic.

One man's tangent is another man's failure to consider the consequences.
Sometimes, the cure is worse than the disease.
It's all a matter of degree.

Regardless, it did not have any relevance to the actual question asked.







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wrote in message
...
On Wednesday, January 15, 2014 12:21:42 PM UTC-5, Bob La Londe wrote:
Then I was wondering if I might get a better

concentricity by heating the part, and letting it cool around the shaft.

Still with a flat on the shaft and a set screw just to be safe.


Please lets not go off on tangents. Thanks for any help or suggestions.



You might consider this as going off on a tangent, but to get the best
concentricity I would join the rough machined parts and then machine the
part.

Dan


I had not considered that. I'll have to think about it for a while. Given
the final rough shape of the part and the tools I have available I am not
sure I have the ability to do that, but it is worth considering. As a side
note, I have already made this part once as a strictly slip fit with a set
screw and it works fair. I was hoping the shrink fit would give me better
results. The assembly is a spinning part and I am trying to remake it with
minimal runout. The part where it attaches to the drive would be very
difficult to machine afterwards both parallel and concentric to the bore. A
press fit is not practical as the only place to press is a pre-machined
precision interface for yet another part.











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"Bob La Londe" wrote in message
...
wrote in message
...
On Wednesday, January 15, 2014 12:21:42 PM UTC-5, Bob La Londe wrote:
Then I was wondering if I might get a better

concentricity by heating the part, and letting it cool around the shaft.

Still with a flat on the shaft and a set screw just to be safe.


Please lets not go off on tangents. Thanks for any help or suggestions.



You might consider this as going off on a tangent, but to get the best
concentricity I would join the rough machined parts and then machine the
part.

Dan


I had not considered that. I'll have to think about it for a while.
Given the final rough shape of the part and the tools I have available I
am not sure I have the ability to do that, but it is worth considering.
As a side note, I have already made this part once as a strictly slip fit
with a set screw and it works fair. I was hoping the shrink fit would
give me better results. The assembly is a spinning part and I am trying
to remake it with minimal runout. The part where it attaches to the drive
would be very difficult to machine afterwards both parallel and concentric
to the bore. A press fit is not practical as the only place to press is a
pre-machined precision interface for yet another part.


P.S. Some machining can (and should) be done after its finished for
balance.




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