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EBay score !

There isn't a day goes by that I don't scour Ebay for deals on all kinds of stuff , I have specific searches that are saved , the results arrive in my email inbox .

I search for ..........

Sunnen
Sioux
Mitutoyo
Kent Moore
Valve seat & guide tooling
Jim's tools ( specialty harley tools )
K O Lee
Van Norman
KwikWay
 
math, because I love math.

Carbon steel temperature coefficient is 0.000006”/“/*F. Stainless steel is 0.000009”/“/*F

So a 6” long round carbon steel bar will grow 0.006” in length if the temperature changes from room temperature to boiling water.

And the circumference will expand 3.14x this, which is why shrink fits work on round shafts and bearing
 
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whydontu said:
math, because I love math.

Carbon steel temperature coefficient is 0.000006”/“/*F. Stainless steel is 0.000009”/“/*F

So a 6” long round carbon steel bar will grow 0.006” in length if the temperature changes from room temperature to boiling water.

And the O.D. will expand 3.14x this, which is why shrink fits work on round shafts and bearing
Click to expand...

Beat me to it! I love math too! Always good to keep the numbers in perspective.
 
Mcgyver said:
Ah ha, you changed in to circumference.....barely slept last night wondering what I was missing! :D
Click to expand...

While we are confessing our brain farts......

Funny how our brains work. I choked too, but not for the same reason. I wondered what happened to the 2.0.

My mind always thinks in terms of radius not diameter. It makes the cos & sin effects easier to instantly visualize. So I instinctively wanted to do 2*pie*r instead of pie*D.

That stupid compound scale is a constant problem for me. Despite the fact that a micrometer or a caliper measures diameter and that ought to make it easier, my brain always hits a wall. I have to give it a kick every single time. It's a nanosecond problem, but I'm pretty sure the impact injuries are accumulating! ;)

Edit - which reminds me. I'm in the middle of scoping out a DRO for my lathe. Should I do the crossslide scale in diameter or radius?
 
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Dabbler said:
Since it is a setting that is easily changed, you might try diameter (what a lot of people use, and what I think might be best) and then try radius, asn see what you like?
Click to expand...

Good point. Another brain fart on my part. Why worry for even 5 seconds about something that is so easily changed.
 
How does that saying go? If one person has a question, odds are there may be others...? LOL
If I did my math right, the circumference comment is correct. 18.8496 / 6= 3.14
But maybe diameter is more relatable & practically measurable?

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I agree Peter!

To REALLY understand a shrink fit, one must also take stress and strain into account. Yes, the metal stretches with temperature. But as it subsequently cools it is also resisted by the bar it is shrinking around and this causes stress and strain in both parts (collar and bar) that offsets the shrinking until everything is balanced.
 
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