press fit instead of shrink fit

[ftp19601960]

I tried to put gear from my auto transmission on a shaft with pre-heating using small 20T press. It goes only 50%. May I simply use cold huge press 150T to put it back?

 

[racookpe1978]

Well, now you have a problem.

Is the part still halfway on?
Did you rip it off, or leave them as-jammed?
What are the actual diameters of the two parts (mic them to at 0.001 to report the overlap and the jam factor.)

What is the length of the area that will be interference fit?
Did you use frozen CO2 to chill either part? Now, or when you tried to fit them together?
What do the parts look like in cross section and in plan view?

 

[ftp19601960]

I cannot pull it back and measure exact inner diameter

.jpg]

http://files.engineering.com/getfil...-6e45-4c53-8569-e480d5ad0d05&file=1124142142a

[1].jpg
Roughly shaft is a tube with 48mm at the interference point and 20mm inner hole.

 

[ftp19601960]

[URL unfurl="true"]http://files.engineering.com/getfile.aspx?folder=a33222f5-6e45-4c53-8569-e480d5ad0d05&file=1124142142a[/URL][1].jpg

 

[tbuelna]

It looks like the gear is made from bronze, or is the color just a result of it being heated?

Frankly, I can't imagine a transmission component requiring such a significant level of interference fit that the force from a 20T press would not be sufficient. Normally, it would not be a good idea to use a press fit for this type of assembly, since the press fit will usually result in smearing/galling of the mating surfaces. A thermal fit works much better. The only issue when using a thermal fit is that you cannot allow the part being installed to stop moving once it engages the mating part. If it does there will be a transfer of heat between the parts and they will immediately seize up.

Since your parts are seized together, there is likely already some galling damage on the mating part surfaces. And it may likely require quite a bit of rework to repair the damage. If you can't separate the parts using force, your best option will be to machine off the part that is cheaper or easier to replace.

Good luck.

 

[byrdj]

How hot was the gear when you tried? If only a ~250F, You might be able to use the delta in thermal expansion betweeen the grear and shaft to sperate. (along with the press).

assuming the gear is brass/bronze with an imperial coef of ~10 and the shaft is commom steel with coef of ~7. if the shaft is a 300SS (non magnitic) your s&*#ed since thier coeef is also ~10.

Heating the gear with a tourch to ~ 500/600F with the shaft also warming so a change of ~400/500F with an Gear ID of 0.8" the interferance fit will open 400/500 X (0.010-0.007) X 0.8 = 0.001/0.0012", which would be the equivialnt of just heating the gear to ~250F. Any means to keep the shaft cooler during the pocess would help even more

 

[ftp19601960]

That's not bronze. It was my desperate attempt to heat it up. It's steel oxidation. Oven temperature was 450F for 1.5 hours with 180C measured by touch on the gear. The shaft was about 32F during pressing. Apparently pressing action was not instant and gear did not slip right away (and I had to use press). I cannot measure ID now apparently but before that gear was removed by 45-50T effort when all was cold. I guess separation is totally different process than pressing in. And by press fitting (vs combined heat/press) I could only destroy it.

 

[geesamand]

Sounds like you're in a tough spot. Those parts could be damaged and any effort to get enough heat/cold into one member could not be enough to free them.

What method of assembly does the OEM service manual say?

David