Rolexes and a high field MRI

[sirjohnbrian]

I did an unofficial test of a my Rolexes in a 1.5T high field medical MRI. I had three subjects: a 36 mm SS datejust purchased in 1990, a SS/gold full size datejust, and the Deep Sea, both purchased last year.

Before entering the MRI suite, all three watches were tested on a pacemaker magnet. There was absolutely no attraction despite the fact they were made of steel. It is known that very high grade steel is non-magnetic. When this magnet was placed about 1cm away from the SS/gold datejust, the watch stopped but restarted after the magnet was removed. If any of these watches were attracted to the magnet, I would not have brought them into the MRI suite.

All three watches, upon entering the 5 gauss line (about 2 meters from the MRI) suffered no adverse effect.

All three watches continued to work until about 1 meter from the magnet.

The midsize datejust continued to work until about 2 feet (.6 m) away from the bore. Both the DSSD and the TT datejust stopped about a meter away.

All watches resumed working after they were removed from the field at these distances.

ALL WATCHES STOPPED WORKING AND DID NOT SPONTANEOUSLY RESTART IF THEY WERE PLACED ANY CLOSER TO THE FIELD.

A simple tap of the crystal was enough to restart all three watches and they did not suffer any long term effects, as far as I can tell.

CONCLUSION: Don’t do this at home. The field strength of an MRI is not spherical and these numbers are purely relative. Even though the case and spring are not magnetic, there must be gears which are and they apparently warp in a strong field. I suspect that had I placed the watches even closer into the bore, I would have permanently damaged them.

I didn’t do this experiment with a quartz watch but knowing how credit cards are affected, I suspect that even at the 5 gauss line, any electronic watch will stop working.

[Tools]

Usually, both the pallet and escapement wheel, and the mainspring are steel....... close enough to a magnet and they will stop moving because they cannot overcome the pull of the strong magnet...

Sounds like any Rolex though, is pretty tough in such an environment..

[escudoturbo]

Would be intresting to see this done on a milgauss

[sirjohnbrian]

Originally Posted by escudoturbo

Would be intresting to see this done on a milgauss

Thought about it but I didn't have one. I suspect that the same finding would have occurred as the "guts" of DSSD are the same.

[sirjohnbrian]

Originally Posted by Tools

Usually, both the pallet and escapement wheel, and the mainspring are steel....... close enough to a magnet and they will stop moving because they cannot overcome the pull of the strong magnet...

Sounds like any Rolex though, is pretty tough in such an environment..

Which obviously leads to the question as to why they don't make it out of the same steel as the case.

[vjb.knife]

Originally Posted by sirjohnbrian

It is known that very high grade steel is non-magnetic.

A simple tap of the crystal was enough to restart all three watches and they did not suffer any long term effects, as far as I can tell.

CONCLUSION: Don’t do this at home. The field strength of an MRI is not spherical and these numbers are purely relative. Even though the case and spring are not magnetic, there must be gears which are and they apparently warp in a strong field. I suspect that had I placed the watches even closer into the bore, I would have permanently damaged them.

You have a lot of guts doing this to 3 rolex watches. I hope they are OK after it.

I have to differ with this part of your statement though. This is a blanket statement that is in whole not true.

"It is known that very high grade steel is non-magnetic."

Certain stainless steels and non-ferrous metals are "non-magnetic" or more correctly have a low magnetic signature. Specifically the addition of nickel can change the structure of stainless steels from magnetic to non-magnetic or martensitic to austenitic. Whether you consider austenitic stainless steels to be "high grade" or not is a matter of semantics or what properties are important in your application. if you are in need of malleability and corrosion resistance like in a watchcase, then yes they could be considered high grade, but if you are making something like a knife or a tool that needs to be hard, durable and could take a sharp edge then austenitic steels like 904L are very low grade, because they will not do the job.