Higher Heat Application Shoulder Screw

[vc66]

Hi All-

I'm using a 304 Stainless Steel shoulder screw that's threaded into a 304 stainless steel plate. The application can reach about 180° Celsius steady state, and will change from there to STP about 6 times a day.

The shoulder screw needs to be removed once a week for cleaning, and the problem is that the shoulder screw is extremely difficult to un-thread after cooling. I am wondering if there is another material I can use for this shoulder screw that may give me better results.

Any input or suggestion is appreciated, and if any more information is necessary, please let me know!

Thanks,

V

Mechanical Engineer
"When I am working on a problem, I do not think of beauty, but when I've finished, if the solution is not beautiful, I know it is wrong."

- R. Buckminster Fuller

 

[CoryPad]

Is any lubricant used between the threads? Stainless on stainless is notorious for galling, which is probably part of the problem you have now.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[vc66]

It's used in Ultra-High Vacuum, so lubricant is a no-go. It's an older design that I'm trying to improve upon. Thanks for the response, and any other comments/suggestions are welcome.

V

Mechanical Engineer
"When I am working on a problem, I do not think of beauty, but when I've finished, if the solution is not beautiful, I know it is wrong."

- R. Buckminster Fuller

 

[CoryPad]

Are you sure graphite or molybdenum disulfide are not allowed? How about simple petrolatum? Silver plating is used for aerospace fasteners that must be lubricant free and galling free. I am not aware of a silver plating process for low volume parts.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[vc66]

It's for use in a process chamber, where there is a cloud of ions of different elements. The less chemicals the better. I will ask if this is possible, but just in case, if there are any other suggestions-they are appreciated. Thanks for your response so far, CoryPad.

V

Mechanical Engineer
"When I am working on a problem, I do not think of beauty, but when I've finished, if the solution is not beautiful, I know it is wrong."

- R. Buckminster Fuller

 

[TVP]

There are other grades of stainless steel that will improve the galling situation. Nitronic 60 for the screw is one option. Two others are Gall-Tough and Custom 455 from Carpenter. You can obtain more information from the Carpenter website:

http://www.cartech.com

 

[btrueblood]

You might also look at using a "plain old steel" bolt, in a higher tensile grade.

 

[MikeHalloran]

I'd try real hard to replace the shoulder screw with a shoulder stud and a clip, so the maintenance involved only removing and replacing the clip.



Mike Halloran
Pembroke Pines, FL, USA

 

[vc66]

Thanks, Mike. That was my initial inclination, but I'm extremely limited with space.

V

Mechanical Engineer
"When I am working on a problem, I do not think of beauty, but when I've finished, if the solution is not beautiful, I know it is wrong."

- R. Buckminster Fuller

 

[MikeHalloran]

For weekly maintenance, it should need no tool more sophisticated than a hammer and maybe a prybar.

...

...

Okay, now I'm thinking of something more sophisticated. A fixed cylindrical sleeve, with an internally engaged plug-in head/flange retained by a mechanism like a ball-lock pin or a Cleco sheet metal tool.



Mike Halloran
Pembroke Pines, FL, USA

 

[vc66]

I was looking towards a split shaft, with a long lead-in and short lead-out chamfer, that would engage ("snap into") the inner diameter.

This opens up a new question... If anyone has any ideas of ways to create this joint, other than a thread, please feel free to comment. I will post up a rough picture tomorrow morning.

Thanks again all.

V

Mechanical Engineer
"When I am working on a problem, I do not think of beauty, but when I've finished, if the solution is not beautiful, I know it is wrong."

- R. Buckminster Fuller

 

[vc66]

Hi All-

Right now, Item 1 is about .2" thick, and can't get any thicker. There will be 4 Item 3's connected to an actuator that force item 1 upwards. There isn't a lot of force seen on these connections, so a completely rigid setup is not necessary. If anyone has any ideas/thoughts, I certainly welcome them.

Thanks again.

V

Mechanical Engineer
"When I am working on a problem, I do not think of beauty, but when I've finished, if the solution is not beautiful, I know it is wrong."

- R. Buckminster Fuller