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Higher Heat Application Shoulder Screw

Higher Heat Application Shoulder Screw

Higher Heat Application Shoulder Screw

(OP)
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

RE: Higher Heat Application Shoulder Screw

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

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RE: Higher Heat Application Shoulder Screw

(OP)
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

RE: Higher Heat Application Shoulder Screw

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: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.

RE: Higher Heat Application Shoulder Screw

(OP)
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

RE: Higher Heat Application Shoulder Screw

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

RE: Higher Heat Application Shoulder Screw

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

RE: Higher Heat Application Shoulder Screw

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

RE: Higher Heat Application Shoulder Screw

(OP)
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

RE: Higher Heat Application Shoulder Screw

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

RE: Higher Heat Application Shoulder Screw

(OP)
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

RE: Higher Heat Application Shoulder Screw

(OP)
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

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