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Extinguish the Flame

Flameless Heat: Hot Tip for Loosening Frozen Fasteners

Alicia Hawkins - Wednesday, June 20, 2018

This guest blog was written by Dan Marinucci, Senior Writer at MOTOR Magazine

Motor Magazine & the Mini-Ductor

The mightiest method for loosening fasteners may be flameless heat. Here's what you need to know about this technique.

Stubborn or frozen fasteners are a frustrating fact of life for automotive technicians everywhere. Although these problems are more prevalent in the snow-and-salt belt, they occur in the milder climate zones too. MOTOR readers probably have their own memorable war stories about loosening frozen fasteners – especially when using an oxyacetylene torch of some kind.

The flameless method, which is powered by electricity, features a process called induction heating. This technology offers substantial advantages over a common torch. First and foremost, induction heating doesn't create an open flame. An open flame is always a potential safety hazard in any auto repair shop. In fact, a hurried tech and a hot torch can be a very risky combination, agreed?

Second, induction heating beats a torch because it only heats electrically conductive metals. (In fact, the greater the iron or steel content in a fastener, the better the process works.) Anyone who has wielded a torch appreciates how difficult it can be to heat a frozen fastener without harming anything near it. This includes, of course, damaging suspension bushings or various grommets – not to mention melting adjacent plastic parts or igniting the vehicle's undercoating. Induction heating, on the other hand, won't heat nearby materials made of rubber, plastic, cloth, etc.

Third, the nature of the process enables it to loosen frozen nuts more effectively than a torch does. Induction Innovations, the manufacturer of Mini-Ductor® brand products, is the major supplier of induction heating tools to the auto repair industry. One of its engineers explained that creating a major temperature differential between a frozen nut and the bolt is the real key to success. Suppose that corrosion or thread-locking sealer is bonding a nut onto a bolt. Out in the bays, we call this a frozen or seized nut.

Anyway, the trick here is to concentrate heat on the nut itself and only the nut. When properly heated, the nut expands. When it expands enough, it breaks the bond of corrosion or sealer between itself and the bolt. Then you can neatly unthread the nut from the bolt. Some techs habitually heat a frozen nut until it's cherry red before trying to loosen it. But usually, the engineer explained, you only have to heat a frozen nut until it's 200 to 300 degrees F hotter than the bolt to expand it sufficiently. In reality, heating a nut to cherry red may be overkill – regardless of the heating technique you're using.

Okay, so inductive heating focuses heat on the nut alone. A common torch, on the other hand, tends to heat both a frozen nut and the bolt simultaneously. Heating both doesn’t create the preferred temperature differential between the frozen nut and the bolt, the engineer said.

Cool Tool Makes Heat

There are three common Mini-Ductor heating tools. Two operate on 120 volts AC; the other runs on a 12-volt DC source such as an automotive battery. A few years ago, MOTOR source Paul Grech urged me to try out a Mini-Ductor heating tool. Grech has operated Allied Engine and Auto Repair in San Francisco since the mid-1970s. What’s more, he has always taken pride in fixing whatever rolls in – foreign or domestic, older or newer vehicle. Based on his shop experience, he gave induction heating method high marks. (When Grech bought the tool, he took it to a trade association meeting to show his buddies. "I loaned it out five times before I got my first chance to use it,"; he told me.

I stowed Grech’s comments in the old "future-story" hopper. Just recently, a Honda specialist reminded me of the topic. Using a Mini-Ductor tool, he made quick work of some rusted suspension hardware under a 2006 Acura TSX. This tech's routine is heating hardware until it’s cherry red. I watched him heat several 17-mm nuts to cherry red in no time flat!

Meanwhile, the popular Mini-Ductor kit I used had a selection of heating elements called work coils. (The work coil is the component that actually heats the fastener you're trying to loosen.) Thankfully, changing work coils entails nothing more than loosening and retightening two thumbscrews.

First of all, the kit contained eight "pre-formed" work coils. Pre-formed means the end of each work coil is already looped or coiled for you – just slip it onto the frozen fastener. These coiled ends were looped into a variety of diameters to accommodate different size fasteners.

Second, the kit provides two cool ways to create your own work coil for specific heating situations you encounter. One is the U-Form coil, a 23-inch long element coil that's very malleable – easy to bend into the shape you need for a heating task. The other item is the"Bearing Buddy" a larger and more-robust version of the U-Form coil. As the name suggests, it's designed to be curled around larger-diameter parts – especially reluctant bearings.

Dan Makes the Heat

I tried the Mini-Ductor on a variety of fasteners that commonly give trouble here in the snow-and-salt region. These included a downstream oxygen sensor, various suspension bolts, fuel tank strap nuts, wheelnuts, and a harmonic balancer bolt. This may stun some readers: I actually read and followed the operator's guide. Per its directions, I only heated fasteners for several seconds and then tried loosening them. Much of the time, the relatively brief heating time worked fine – the fasteners loosened up without me heating them cherry red first.

What's more, I tired the tool on old parts in some shops' outdoor scrap piles – stuff left out in the elements. I was pleasantly surprised at the hardware I could loosen with just a long-handle ratchet after heating it with the Mini-Ductor. Simply put, this induction heating technique is a winner. From now on, I won't work without it.

Wow, it's that time again. I’ll look for you here next month. Meanwhile, the shop manager claimed he heard an ice cream truck's ting-a-ling nearby. That's groovy because I'm hankering for a Nutty Buddy.

Contact us to learn more about the Mini-Ductor portable induction heater


Induction Innovations, Inc.

U.S. patents: 6670590 and 6563096 apply to all products; D707,804 and D728,086 apply to handheld, inline induction heaters; patent pending for the Mini-Ductor 12V (MD-500)
European Patent Office (EPO): patent 002076372-0001 applies to all handheld, inline induction heaters; patent pending for the Mini-Ductor 220V (MD-800) and Mini-Ductor 12V (MD-500)
Australia patent: 343968 applies to all handheld, inline induction heaters