heat shrink fit

[whateg0]

4" and up....
Less than that, you aren't going to get a .005" shrink.
2" bore....I have got up to .002".

So my 0.9" never stood a chance?

[warmstrong1955]

4" and up....
Less than that, you aren't going to get a .005" shrink.
2" bore....I have got up to .002".

So my 0.9" never stood a chance?

Ummmmm.....no.

[John Hasler]

I understand that. I'm interested in the case where the hole shrinks when the entire part is heated uniformly as Bill reported.

I've cheated oversize bores for years, just by heating them, uniformly, and then letting them cool on their own.
Most I have done, were with larger bores, and done correctly, you can shrink them up to .005", and pretty much still round.

Bill

Sure, but I'm interested in the case where a bore was smaller with the entire piece hot than it was when cold before you started.

[John Hasler]

4" and up....
Less than that, you aren't going to get a .005" shrink.
2" bore....I have got up to .002".

So my 0.9" never stood a chance?

500 F should get you .005" on a .90" hole in aluminum.

[rudd]

One thing I considered after looking at Liveaboard's post at the top - that red hot block is going to transfer quite a bit of heat into the shaft. The block is then going to shrink, with the shaft being the last to cool. I think it's quite possible the shaft will be "shrunk" by this, leading to less interference than planned.
300 degrees will get you .002 in a 1" dimension. And that isn't hot enough to deform the internal part.
https://www.utausa.com/metalconverter.html

[liveaboard]

For that application, deformation was allowable and expected. But it's beyond by abilities to discern.
I had a slight taper cut into the end of the shaft and whacked it in quickly with a large hammer.

The bolt heated up very fast; but didn't appear to achieve red heat.
On cooling it seems suitably stuck.

I used an online calculator for heating this ring to fit over the hub. The 4" hoop only needed a couple of hundred C supposedly.

It should have just slipped on, but even though I used more heat than specified there was some interference.
Fortunately, I was ready with a hammer and had something below to hit against.
Next time I do something like this, I'll use a lot more extra heat. Hammering thin hot parts as they shrink and bind isn't really nice.
Anyway, the part did its job.

[John Hasler]

I use the press in preference to a hammer whenever possible. I ruined too many parts with a hammer.

[whateg0]

I use the press in preference to a hammer whenever possible. I ruined too many parts with a hammer.

When all you have is a hammer, everything looks like a nail! Seriously, though, when time is of the essence a quick blow from a hammer might seem preferable to the relatively slow action of a press. If I had to choose between a fast arbor press and a hydraulic press for this, if still think the about press a better choice. In my case, it didn't have enough oomph though.

Dave

[toglhot]

The way I do is turn to a shrink fit size, heat the female and freeze the male. You can never get it all the way through without the pin heating up and expanding. Work quickly and have a bloody big hammer handy. A vice will often help if a hammer is not desirable.

[John Hasler]

A hammer is never desireable but it is sometimes necessary. I often used a vise before I got my Dake. I find that if I have properly designed and set up my fixture, gotten my temperatures, soak times, and clearances correct, and work quickly the part always goes in smoothly.

Of course, pretty often I just cook the pin with the torch while holding it with tongs until it looks right. I usually get away with it.

[warmstrong1955]

You have to have a plan, and be ready.
I’ve dropped frozen bearing races into heated up bores, and had them slide right on in only to bounce up, and stick where they bounced up to. Doesn’t take long to lose the clearance you once had.

[liveaboard]

had them slide right on in only to bounce up, and stick where they bounced up to.

Now that's got to be aggravating!