Press fit problems 2

[PrecisionT]

First off I am new here so HI all..... Now the problem. I am trying to press fit a .125/.1253 X .312 416 stainless pin at a 40HRC into a .124/.1245 hole in 154CM at 58HRC and it must pass threw the part and stick out .086 off each side. Both the pin and hole are chamfered but when I press the pin in it just peels off the material from the pin and it is then loose in the hole more like a slip fit. I have tried shrink fitting this with dry ice/acetone with the same problems. Any help would be greatly appreciated.

Thanks, Travis

 

[hydtools]

mfgenggear, the edge problem is with the hole not the pins. The pins are being peeled.
Yes, I think it would help. Going to a harder pin will help, too.

Ted

 

[mfgenggear]

hydtools

I having one of those days. LOL

Mfgenggear

 

[PrecisionT]

I will give it a try, the 30 deg, and yes I think the harder material will help the most. I will be ordering some 440 tomorrow regardless of the lube outcome. And thanks again for all your help it's extremely nice to have a place like this for idea's.

Travis,

 

[Tmoose]

Even with a shallow taper I blend and polish the transition to a radius. it does not take much of a corner to cause pain and discomfort. Moly past should help with galling. Some folks in motorsports attribute mythical qualities to Castor based oil when used as a press lube. I can testify Sunnen's press lube was pretty impressive as recently as the late 80s, taking all the slip-stick out of a steel/steel interfence fit, and lowering the static friction about 50% or maybe more, which is not always a good thing (pressed together crankshafts).

http://www.goodson.com/Sunnen_Press_Fit_Lubricant

 

[MikeHalloran]

I'd take the chamfer down to 7 deg included on both parts.

Mike Halloran
Pembroke Pines, FL, USA

 

[PrecisionT]

Well I tried the MolyKote. It did dramatically reduce the shaving/peeling effect and made the pin go in much easier but the pin also came out almost as easy. So I will have the 440 tomorrow and we will see what that does hopefully it is the hardness difference that is making this so difficult.

MikeHalloran, I have taken it down to 30 so far on the hole but no real noticeable difference. I can take the hole down to 7 but I can not take the pin it must stay at 45.

Travis,

 

[mfgenggear]

precision

thanks for letting us know.


Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.

 

[israelkk]

PrecisionT

What is missing in the tests you make is the actual interference on each test you tested. If you do not test the extreme interference of 0.0013" beware of any conclusions you draw from your tests.

 

[byrdj]

Just some thoughts...
Could a "spring" roll pin be used?
how about a groove down the pin?

 

[btrueblood]

After inserting the pin with Molykote, try baking the assembly at your upper limit temperature (375F?) for several hours to cook off the lube.

 

[PrecisionT]

Well I just want to say thanks to everyone for the help it is most appreciated. We did fix the problem with the material change so all is good. Again thanks.


Travis,

 

[mfgenggear]

Thanks Travis

Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.

 

[Tmoose]

"It did dramatically reduce the shaving/peeling effect "

Any shaving is too much when pressing parts together.