heating a ring 2

[Junid]

Hi,
I want to install a ring on a shaft.
The shaft is a tungsten carbide.
The ring is a AISI 303.
The ring must be installed with a press tolerance, to insure no movement of the ring.
The dimension of the shaft is: 0.1250" h7 (0.1250" +0.000-0.0005 )
The dimension of the ring is: 0.1250" R8 (0.1250" -0.0006 -0.0013 )
I tried to install the ring after heating by pressing. But the result is no sufficient.
The ring got no cylindrical, the width of the ring changed,the ring was crushed inside.
My questions are:
1. How the heating process must be? What is the temperature, time …
2. Do I have to change the material of the ring to another material?
3. Is the tolerance of the ring for fit with press?
Thanks

 

[unclesyd]

A little more details would help.

Overall dimensions of the 303 SS ring/cylinder.

How far is the ring located from the end of the shaft?

For recommendations for a new material.

What is the purpose of the ring?

Do you require SS?

 

[Junid]

The ring dimensions are: 0.195X0.079X0.125
Out diameter: 0.195"
Hole: 0.125"
Height: 0.079"
The ring located about a 0.234" from one side of the shaft, and in the other side is 0.3563" (shaft lenght is 0.669")
The purpose of the ring is a stopper in the machine.
One of the considerations is that the ring will not become rusty. So stainless steel is an option, and we have a stock of it.

 

[MikeHalloran]

One problem you face is that the time constant of the ring is very short.
... so there's not enough time to remove it from a furnace, transfer it to a press, and push it on before it cools.

So I'd suggest direct resistive heating or induction heating, and insertion of the shaft while the ring is still in the heating rig, then shut off the heater power and let the ring shrink in place.

The alternative is moving and placing the ring while also holding a torch on it to keep its temperature up. That's not so difficult for, say, a locomotive tire, but for your little tiny ring, it's real tricky.




Mike Halloran
Pembroke Pines, FL, USA

 

[hydtools]

Since the thermal coefficients are about 10x10^-6 for stainless and 4x10^6 for the carbide, you could probably heat both to the same temperature and assemble in the hot environment. Then let the assembly cool.

Ted

 

[Junid]

I changed the tolerance of the ring to P7
so the tolerance now is 3.175 -0.0003" -0.0008"
I wish pressing without heating will be sufficient to install the ring

 

[tomwalz]

What grade of carbide are you using?

You know, at least, what the cobalt content is?

Is your ring completely round? Is it completely round when it's hot? Is it completely round when it cools? If your ring distorts it all it could be enough to cause serious problems.

We have seen issues with rings cut out of rolled material that distort when heated and then cooled. The distortion reflects the rolling process.

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.

 

[unclesyd]

In your application is it possible to have your stop be integral with your rod, in other words have rod ground with stop?

 

[BrianE22]

Are you scraping materal (gouging shaft or ring) during the press fitting? That may account for some of the non-roundness. Can you cool the shaft? Dry ice will cool it quite a bit. (I don't know how well carbide handles cold though.)

Getting the ring square to the shaft for starting is important. Do you have any special fixturing that does this?

 

[tomwalz]

Dry ice won't bother carbide.

You could braze the ring in place.

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.

 

[btrueblood]

Star for Mike's 1st post, and Tom's last. Having tried to heat and fit rings on 15" precision-turned cylinders and rings...it's no easy feat. On a ring as small as the OP's I'd say it's a non-starter, in my oh-so-humble opinion.

 

[Junid]

After I changed the tolerance I press the ring without heating, and I checked the result and it is ok.
When I installed the ring with heating the dimensions of it were changed and it become non-cylindrical.
For your information the grade I use is IC4, and I think that cooling the shaft (tungsten carbide)with dry ice will not work, but possible to try this.
thanks a lot