If you have been handed MRI work without a background in it, the first surprise is not the physics. It is that the tools you already own cannot go in the room. This covers what actually belongs in an MRI-safe kit and the fastener sizes that come up most on scanner work, so you turn up with the right thing rather than find out at the magnet.
It is written for the technician who services CT or general imaging and now covers MRI occasionally, and for anyone building a first kit. Sizes vary by platform, generation and how a system was installed. Treat all of this as the sizes you will reach for most, not a parts list.
Why your existing tools stay outside the door
The magnet is always on. It does not power down between patients and it does not stop pulling on steel because you are being careful. A chrome-vanadium socket set is a projectile hazard inside Zone 4, and the field does not have to be 3T for that to matter.
Grade 5 titanium (6Al-4V) is non-ferrous and non-magnetic, so it does not respond to the field at all. It is also around 40% lighter than steel and corrosion resistant, which matters in a room that gets wiped down constantly.
One correction, because it gets repeated: titanium is not non-sparking. It will spark on impact. Non-magnetic and non-sparking are different properties, and titanium tools are the former. More on what MRI-safe actually means.
17 mm, if you only buy one thing
Across both major platforms, 17 mm turns up more than any other size. It is on Siemens ramp cable work, on GE rear pedestals, and on a large share of cover and panel bolts on both. If you own one titanium wrench, own this one.
It is also the size worth owning in more than one form, because the same fastener shows up in three different situations:
- A 17 mm combination wrench for open access.
- A 17 mm ratcheting combination wrench for cover bolts and pedestal work, where there is almost no swing and a plain wrench turns a few degrees at a time.
- A 17 mm deep socket for places a standard socket cannot reach at all — on a GE bridge it is often the only thing that will seat.
Common sizes on Siemens MRI
19 mm — gradient cable connections
Gradient cable terminations run 19 mm. Covered by the 19 mm combination wrench or the 17 × 19 mm double open-end, which gives you both of the sizes you use most in one tool.
17 mm — ramp cables and general work
Ramping work, cover removal, panel hardware. This is the workhorse described above.
22 mm — RF connections
RF connection hardware runs into sizes past where most general-purpose sets stop. 22 mm is a common gap. Covered by the 22 mm combination wrench or the 21 × 22 mm double open-end.
27 mm and 32 mm — larger RF connections
The bigger RF connections call for both, often used together. Almost never present in a standard kit. The 24 × 27 mm and 30 × 32 mm double open-end wrenches cover them.
24 mm — rear support on whole-body systems
Rear support hardware on whole-body configurations. Covered by the 24 × 27 mm double open-end.
5 mm hex — table covers
Patient table covers commonly take a 5 mm hex. Small, easy to overlook, and the table is the part of the system you touch on nearly every call. Covered by the 5 mm hex key.
Torx — covers and enclosure panels
Siemens uses Torx extensively on covers and enclosure panels, and it is missing from most general-purpose kits. Covered by the titanium Torx key range.
Bracket, clamp and panel hardware
Smaller M4, M6 and M8 hardware appears throughout brackets, clamps and panels. These commonly take 7 mm, 10 mm and 13 mm respectively, though head standards vary. All three are in the metric combination wrench range.
Common sizes on GE MRI
17 mm deep — the bridge
The bridge is where a standard socket runs out of depth and bottoms out before it seats. A deep well clears it. This is the single most common reason someone buys one deep socket rather than a whole set. Covered by the 17 mm deep socket, 3/8" drive.
10 mm — coldheads
Coldhead hardware runs 10 mm. This is scheduled, predictable work rather than a breakdown, which makes it worth having covered properly rather than borrowed. Covered by the 10 mm socket or the 10 mm ratcheting combination wrench.
17 mm ratcheting — rear pedestal and covers
Rear pedestal hardware and a large share of cover bolts are 17 mm, in positions with very little swing. A ratcheting head is the difference between a five-minute job and a twenty-minute one. Covered by the 17 mm ratcheting combination wrench.
A thin-shaft Phillips — tight electronics positions
Some fasteners inside gradient and amplifier cabinets sit where a standard driver simply will not fit. The constraint is shaft thickness, not size. Covered by the Phillips screwdriver range.
The sizes a standard set misses
If you buy a general-purpose non-magnetic set, these are the gaps that send you back to the van:
- Anything above 19 mm. RF connection work runs to 22, 24, 27 and 32 mm, and most sets stop at 19. We carry all of them as fixed wrenches, but if you only meet these sizes once or twice a year, a titanium adjustable wrench covers the whole range in one tool and is the cheaper way to stop being caught out. Buy the fixed sizes when the work becomes regular.
- A deep socket. One 17 mm deep well solves the GE bridge. A standard socket will not reach it.
- A ratcheting wrench. Cover bolts and pedestals are tight on swing, not on torque.
- Torx. Used heavily on Siemens covers and absent from most general kits.
- A thin-shaft screwdriver. Clearance, not size.
What belongs in a first kit
If you cover MRI occasionally rather than full time, you do not need a full service set. You need the common fastener sizes in titanium and not much else.
The 17-piece kit covers hex keys, combination wrenches, open-end wrenches, screwdrivers, pliers and cutters — the fasteners you meet on covers, panels and the table. It is the right starting point when MRI is not your main work.
If MRI is a regular part of your week, the 31-piece Siemens kit carries the wrench range up through the larger RF sizes, and the 40-piece GE kit adds 3/8" drive sockets, a ratchet and extensions for bridge and pedestal work.
For socket work specifically, the 16-piece 3/8" drive socket set includes the 17 mm deep well rather than leaving it as a separate purchase.
Everything is Grade 5 titanium and every kit ships free over $200. Why titanium rather than the other non-magnetic options.
The carry-on kit: what fits in your bag
Titanium is roughly 40% lighter than steel for the same tool. If you carry a kit through airports every week, that is a difference you feel by the end of the year, and it is a reason people buy titanium that has nothing to do with a magnet.
There is a second reason that matters more. TSA allows tools 7 inches or shorter in carry-on baggage, measured end to end. Most tool listings only publish shaft length, which tells you nothing about whether a tool clears that limit. We measured ours overall:
- Phillips #2, 3-inch shaft — 6.25 inches overall.
- Phillips #1, 3-inch shaft — 6.5 inches overall.
- Flat 1/4 × 3" — 6.25 inches overall.
- Flat 3/16 × 3" — 6.5 inches overall.
- Flat 5/32 × 3" — 6 inches overall.
- 6-inch adjustable wrench — 6 inches.
- 6-inch slip-joint pliers — 6.25 inches.
- Hex keys, 10 mm and below — all under 6 inches.
The rule that falls out of this: any of our screwdrivers with a 3-inch shaft or shorter comes out between 6 and 6.5 inches overall, which clears the limit with room to spare. A 4-inch shaft lands close to the line. If you are packing to fly, stay at 3 inches and under.
Above 10 mm the hex keys get long, but nobody carries those every day anyway. The everyday-carry sizes are the small ones.
Why an MRI engineer would want one
Anyone who flies to sites has had the trip where the airline loses the bag and the tools are in it. A small non-magnetic kit that stays in your backpack covers the quick job you get pulled into, the site visit that was supposed to be a look-and-see, and the morning your checked luggage is in a different city.
It is a different kit from your service set. It is not meant to do a coldhead. It is meant to mean you are never standing in a magnet room with nothing you are allowed to use.
We build exactly that kit: the 13-piece titanium carry-on kit is the six tools above plus a 7-piece hex set, every piece measured under the limit. It works out cheaper than buying the pieces one at a time.
Everything above is Grade 5 titanium, non-ferrous and non-magnetic, so the same kit that travels well is also the kit that goes through the door with you.
Who else buys titanium tools
The magnet room is how most of our customers find us, but it is not the only reason titanium is the right material.
Corrosion. Titanium does not rust. That matters in marine and offshore work, in wash-down environments, around salt water, and anywhere a steel tool left in a damp bag comes out ruined.
Magnetically sensitive work beyond imaging. Anywhere a ferrous tool would disturb an instrument, a sensor, or a magnetic-influence device, non-magnetic tools are the answer. That covers research and instrumentation work, precision measurement, and EOD. Note the limit again: titanium is non-magnetic but it is not non-sparking, so it is not a substitute for beryllium copper where an explosive atmosphere is the concern.
Weight. Some people buy titanium simply to take several pounds out of a bag they carry all day.
Frequently asked questions
What size wrench do I need for MRI work?
17 mm covers more than any other single size across Siemens and GE. Beyond that, 19 mm on gradient cable work and 22 mm and up on RF connections. Sizes vary by platform and generation, so treat these as the common ones rather than universal.
Why do I need a deep socket for MRI work?
A standard socket bottoms out before it seats on some hardware, most commonly on a GE bridge. A 17 mm deep well clears it. It is the most common single-socket purchase for that reason.
Do I need titanium tools for CT?
Not for safety. CT, X-ray, mammography and cath labs have no magnet, so ordinary steel tools are fine in those rooms. People still buy titanium for CT work for other reasons — weight, corrosion resistance, or carrying one kit that works in every room in the department.
Are titanium tools non-sparking?
No. Titanium will spark on impact. It is non-magnetic and non-ferrous, which is what matters in an MRI suite, but it is not rated for explosive atmospheres.
Can I take titanium tools in carry-on baggage?
TSA allows tools 7 inches or shorter in carry-on, measured end to end. Our screwdrivers with a 3-inch shaft measure 6 to 6.5 inches overall, the 6-inch adjustable wrench is 6 inches, and hex keys 10 mm and below are all under 6 inches. Length is only half the rule: TSA also bars hammers, drills, saws and crowbars from carry-on at any size, though nothing of that kind belongs in an MRI kit anyway. The screener always makes the final call.
What is Grade 5 titanium?
Grade 5, also written 6Al-4V, is titanium alloyed with 6% aluminium and 4% vanadium. It is the standard structural titanium alloy and the one used for MRI-safe hand tools, chosen for strength rather than purity.
Can I take a stainless steel tool into the magnet room?
Some stainless grades are weakly magnetic and some are not, and you cannot tell by looking. The field does not care what the label says. Anything going into Zone 4 needs to be verified non-magnetic, which is why dedicated titanium tools exist.
What is the most useful single size to own?
17 mm, and it is worth owning three ways: a combination wrench for open access, a ratcheting wrench for tight cover and pedestal work, and a deep socket for places a standard socket cannot seat.
Who buys MRI-safe titanium tools?
Field service engineers, in-house imaging and biomedical engineering teams, and independent service organisations covering MRI. Beyond imaging, titanium hand tools are used in marine and offshore work, research and instrumentation, and anywhere weight or corrosion resistance matters.
