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How to tighten a round Stainless Steel Cap without marring or contaminating it

Keeping it simple, here is my problem/question. I have 316 Stainless Steel cap nuts (1/2"-13 internal thread) that have been electropolished and passivated. These nuts hold a 316 SS memorial plaque to a headstone. The caps are 1" diameter by 1" high and are perfectly round and smooth with no way to get a wrench on them to torque them up to say something in the 50 ft-lb range. Any suggestions on how to achieve this without contaminating the stainless would be greatly appreciated. I don't want rust developing on something that will be outside for a very very long time. The only thing I could think of would be to wrap the SS with .01" Brass shim stock and use chain type visegrips but I don't know if the Brass would contaminate the SS in some way.

Thanks in advance.

Herb Galbraith
Hobbyist - Toronto, Ontario, Canada
June 16, 2011

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Hi, Herb. A "strap wrench" ⇨
is probably what you are looking for. They are made to get a good tight grip on round objects. The strap can be made of metal or non-metal, but most commonly they are a heavy canvas for strength plus friction. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
June 2011

I take about 2 inch strip of plain white paper about 3" long and fold it twice to give a strip about 1/2 x 3. Wrap this around the nut and use a good pair of channel lock pliers. Grip hard and you can get the torque that you need without harming the nut.

James Watts
- Navarre, Florida
First of two simultaneous responses -- June 17, 2011

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Thanks Ted:
I've tried several types of strap wrenches but they all seem to slip and I can't develop much torque on the cap with them. The brass/chain visegrips seems to work reasonably well but I am concerned that the Brass may contaminate the stainless in some way. Does anyone know if I will have corrosion problems with the stainless if there is some Brass contamination?

Herb Galbraith
- Toronto, Ontario, Canada
Second of two simultaneous responses -- June 20, 2011

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Herb,
No worries about contamination from brass, there is no iron in it. At worst you may damage the passive chrome oxide layer a little, but 316 is a very good grade of stainless so I wouldn't worry too much. Heaven forbid you do ever see rust on the nuts later on, you can repassivate them in place with a citric acid based product.

Ray Kremer
Stellar Solutions, Inc.

McHenry, Illinois

July 6, 2011