Frequently Asked Questions

General Questions

The N52 magnets exert the following force:

2 inch x 2 inch magnet – 450 lbs

1.5 inch x 2 inch magnet – 320 lbs

When used with the Magnetic Amplification Handle, the magnets exert more pressure but the exact amount is not known.

The RAT tool also exerts more pressure but the exact amount is not known.

The MDRS was actually awarded 2 separate patents: 1 for the concept of the tooling assemble and 1 for the concept of marketing the tools as a shop setup/kit. During the process of our patent application we found the 2 other BIR tools that have received patents: The Ferree’s mouthpiece puller, and the Ferrees Concept wood and metal dent balls.

The learning curve for MDRS use is very shallow. If you have any experience working with brass instrument repair, you will pick it up very quickly. We do highly recommend working out the curve on a few junkers or stock instruments first. Or, if you live in California, Florida, Hawaii, etc., Wayne or Eric will come to your shop during the winter months in exchange for travel expenses, rental car (convertible), room and board, and $500 a day to personally train you and your staff.

Do you have 10 each of the following horns come into you shop each year: baritone horns, euphoniums, baritone saxophones, tubas, sousaphones, marching baritones? If you have those 60 instruments come in, most (if not all) will have inaccessible dents in the boot and/or the first branch. In the past, since you are not going to disassemble every instrument to remove dents, you probably sent the great majority of those instruments back to your customers with the dents still in them. If you charged each customer only $25 per instrument to remove such dents, you would have enough extra income to pay for the MDRS Ultimate Shop Set Up. Of course, you will charge more than $25 per instrument (unless you are completely nuts), therefore without the MDRS you are missing out on a lucrative profit center.

If you are a person who has never experienced MDR and you just want to see how it works, the Introductory Kit could be a good option for you. However, if you are in a working repair shop, you are not going to be happy with the limitations of having only the basic MDR tool that is included in the Introductory Kit. We suggest that if you are repairing brass instruments in a working shop, you should consider starting out with the MDRS Essential Shop Set Up.

To answer this question, please follow this link:  You will find a wealth of interesting facts about magnets, properties, and uses.

The MDRS and the Dent Eraser are not the same, some of the differences are:

1.The MDRS™ differs, as it is a series of 3 to 4 separate tools rather than just one single tool as in the Dent Eraser™.  Having 3 to 4 different tools, the MDRS™ allows the technician to have various strength tools. This allows the technician to adjust for deviation of metal thickness and hardness and the ability to get into tight areas.

2. According to the inventor of the Dent Eraser™, the magnet/s used in this tool are wholly indigenous to their product having been developed specifically for it’s use by means of a special process and therefore are a completely proprietary and different species of magnet from any and all of the Rare Earth magnets used in the research and development of the MDRS™.

The magnets used in the MDRS™ are very different. They are made from intermetallic compounds that include one or more rare earth elements. The elements are melted together and then milled into a powder that is sintered (pressed and heated), aged and then ground to dimension all within the presence of a magnetic field.  The majority of these magnets are actually made in China, as they are the source for many of the rare earth elements needed for the production of this magnet. Magnets used in conjunction with MDRS™ are also less expensive.

3. The MDRS™ uses a variety of different sizes and strengths of magnets compared to the one magnet used on the Dent Eraser™.  Most of the magnets used on the MDRS™ are either 1″ or 2″ in thickness so they resist fracturing and are much more durable than the 1/2″ thick magnet used on the Dent Eraser™.  The MDRS™ also uses a PVC containment cup and a plastic cap to surround and to protect the magnet.

4. The MDRS™ uses a smaller diameter handle covered with an anti-fatigue foam, which most believe to be more comfortable with prolonged use and easier to maneuver than the larger 2″ plastic covered handle used on the Dent Eraser™

5. The MDRS™ uses not only the solid steel ball from 1″ to 3″ in 1/8″ increments, but also hollow steel balls which range in size from 1.5″, 2.0″, 2.5″, 3.0″ 4.0″ and 5″ in diameter. This allows the technician the ability to do better dent work because of the flexibility to adapt various size balls to fit many different tubes, bows, andbranches .  The hollow steel balls have the additional benefit of being lighter and requires less effort when compared to the solid steel version. With the Dent Eraser™ you have 4 solid steel balls to do all your dent work that are approximately from. 1.5″ to 2.5″ in diameter.

6. The MDRS™ uses a variety of materials and methods to protect and keep the tool from scratching the surface of the instrument.  The UMI Dent Eraser™ recommends the use of Velcro discs,  or a silver polish cloth wrapped around the magnet to protect the instruments’ surface.

7. The MDRS™ has been developed by many experienced band instrument repair technicians and musical instrument manufacturers from the US and abroad.

8.  The MDRS™ handle is tapped and drilled so an eye – bolt can be attached to the end.  Then using the Ferree’s L13 tuning slide remover (slide hammer) hooked to the eye – bolt dents, can be removed in a similar fashion like an auto body dent puller.

9. The new metal “Mag Shields” allow you to change the material on the end of each tool, protect the magnet face while retaining all the original pull strength to remove dents.

10. Also our exclusive “magnetic amplification bar extension” (MABEXT) which allows you to increase the strength of each tool and makes heavy dent removal work easier when used with the N50 magnets.

No you will not, as the magnet is only strong enough to lift up dents when using a 1.0″ or larger metal sphere inside the instrument. The magnets strength is dependent upon the surface area of the metal ball it’s drawn to while removing dents. Another factor is as the tubing gets smaller in diameter there is an increase in surface radius making the tubing much stronger. So a metal ball 1/2″ in diameter does not provide enough surface area to be effective on a tube that is physically stronger. However we are working with spherical magnets to test their effectiveness on instruments like flugelhorns and trombone main tuning slides.

No. Using the MDRS™ will allow you to remove many dents not accessible without disassembling the instrument.  Not all dents can be lifted up using this system but using various tricks will allow you to do many things with less time. The system does have a high learning curve but with experience you can do very good work.  It’s as easy to do bad work as it is to do great work using this or any method.

You should always be careful and keep all metal tools a safe distance away from your working area when using the MDRS™.   10 feet for any computer related equipment, 5 to 6 feet for all other metal objects as a general rule.  Credit cards would almost have to be placed directly upon the MDRS™ to have an effect.

Ownership & Use Questions

Currently, the N52 magnets used in MDRS tools are the state of the art. The patent for Rare Earth N52 magnets is actually held by General Motors. During MDRS research and development, we experimented with many sizes and configurations of magnets. We found that stacking two 2″ magnets on top of each other provided no greater dent removal capacity than simply altering the handle set up. We also ordered a 3″ x 3″ N52 magnet and made a tool with it. This tool delivered no greater dent removal ability that a 2″ N52, but was very cumbersome, heavy and ergonomically unfeasible.

We seriously worked on this concept during the MDRS research and development but discarded the idea for on very important reason: your finger are more valuable than any amount of money. We manufacture and assemble all of the MDSR tools, and we are here to tell you that the final assemble process is not for the weak of heart. Once an Armor Plate disc is applied to a 2″ N52 magnet, it requires a very concerted effort to remove it even by someone who works with making the tools regularly. Someone trying to pry the discs on and off the magnet is going to harm themselves, damage the magnet, or both. Purchase both the the tools, they will quickly pay for themselves and you can enjoy using them with all of your fingers!

Awesome! Let us know what other great items you find.

We did not think of using MDRS on horns when we were first developing it, and none of our R & D was ever performed on horns. However, NAPBIRT member Jim Thomas has developed methods of using the MDRS in horn repair, and we suggest contacting him to discuss the subject.

For most applications of normal dent removal, you are going to want to own the Essential Shop Set Up. However, if you want to be able to perform all of the horrible dent removal examples in the tutorials section of our website, you are going to also need the 2″ RAT. Working with saxophones, you are probably only ever going to need the B ball set.

In our research and development, as well as in our day-to-day repair activities, we have come to believe that these tools are the most commonly used tools in the set. Any working repair shop interested in MDRS should first and foremost own these 2 tools.

By their very nature, the hollow balls have less attractions to the magnets than the solid balls. They are perfect for many dent removal applications and burnishing work, especially on instruments that have thinner, soft brass such as German tubas. The small holes are threaded by the manufacturer, then painted or plated, and depending on their size, become the top of a 10′ or 100′ flag pole.

In our opinion, if you possess a set of MDRS tools, there are only 2 places those magnets should ever be: 1. On your work surface. 2. In the caddy where they are protected and out of harm’s way. With the caddy, you do not have to wonder where you set your tool and what trouble it is getting into.

Here is a simple test to perform after you receive your tooling: Place a medium sized ball on a flat surface. Take any one of your MDRS tools and lay it also on the flat surface with the face of the magnet pointing toward the ball. Starting with the magnet about 2 feet away from the ball, slowly move it toward the ball. You do not want the ball to fly toward the magnet, you want to find the point in space when the ball will just start to quiver from the magnetic field. That space between the ball and magnet at the movement points is the effective distance of the magnetic field of the magnet you tested. Keep it that far from computers, credit cards, hearing aids, pace makers, open cans of cork cement, razor blades, and all other magnetic materials to avoid having problems with any MDRS tool.

The Mylar discs we send with every order are actually only single of double ply clear drum heads from which we cut the rims off. If your shop or music store deals at all with percussion, never again throw away old bottom snare drum heads!

It is a multi-purpose tool. Unscrew the eye bolt from the end of a tool and screw on the extension handle. It balances out the tool a bit, but you will also notice an increased magnetic ability. During research and development, we worked with an Emeritus Professor of Magnets from Michigan State University who was a pioneer developer of the Atomic Particle Accelerator at MSU. He taught us about increasing and altering magnetic fields: A cylindrical magnet 2 inches in both length and diameter has on its left side a north pole of 1 inch, and on its right side a south pole of 1 inch. Attached to the south pole is the 5″ x 1″ metal bar handle. The south pole of the magnet is drawn into the bar, increasing the size of the north pole and making it stronger. Attaching the extension handle will make the entire magnet the north pole and the handle assemble the south pole. Want to increase the power of the magnet even more? Unscrew the head of one of your other magnets, unscrew the eye bolt from the end of the handle, and screw the head onto the end. You have now created a tool that resembles a miniature barbell with a magnet on each end that act as the poles and are now much stronger. For convenience, you can also set up a tool that is flat on one end and round on the other, eliminating the need to switch tools while working on a job.

We have never had to have a return policy since we have never had a return request. The MDRS is dent removal technology for 21st century repair technicians. If you receive your MDRS and for some reason are not 100% satisfied wit it, please make sure you’ve taken the end caps off.

The Armor Plate end caps were the biggest innovation made after the invention of the tooling. If you have the original MDRS tooling that used pad slicks and Velcro, and have not yet returned them for upgrade, you are really missing out. The end plates are made of high carbon tool steel and are first heat treated to a specific Rockwell hardness and then sent to a company called Tech Metal, where they apply a finish called Armor Plating. These processes make the end plates impervious to cracking, splitting, chipping, and denting. They should hold up to a lifetime of hard use.

Think for a moment: every time you put your instrument to your lips, do you play fortissimo? Probably not. You play fortissimo, pianissimo, and everywhere in between. Dent removal is very similar. Let’s imagine you have an instrument with a dent in it that is made of thin soft brass and you were to flap onto it a 2″RAT. You would be creating more damage than you started out with. To eliminate the possibility of this happening, we do not sell the 2″ RAT to any technician no on file with us as having preciously purchased the essential tooling. You have to use finesse in MDR just as you would with a ball on a rod.

The magnetic strength on the surface of the flat faced MDR tools is the same over the full face of the tool. With the RATs, the full strength of the magnet is focused to the apex of the dome, providing increased power for more difficult dent removal operations, and increased power to remove dents form smaller tubing. The increased focused power of the RATs enables removal of wrinkle, ping and crease dents that resist removal with the flat faced tools.

Whatever means of lubrication you use, and whatever buffer you choose to use (Mylar, chamois), you need to make absolutely certain that the surface and buffer are clean and free of any sort of metal filings, dist, debris, dirt, etc., as these will all cause unnecessary scratching and hinder the best flow/glide of the magnet across the work surface. We recommend a good quality commercial spray wax because it is usually no fuss, no muss. If you look at the contents, many spray cleaners no longer contain any sort of wax.

A dent hammer that works very well and not attracted to the MDRS™ are the ones made by Votaw tools.  These hammers are stainless steel and aluminum with a Delrin handle.  They work great for all types of dent work and are perfect in this instance.

No, using a dent ball with a threaded hole or the barrel ball with flat ends does not work well.  The hole or flat side/end always positions itself towards the magnet, which will create ridges, and ripples that compound the problems you are trying to alleviate.

No you will not, as the magnet is only strong enough to lift up dents when using a 1.0″ or larger metal sphere inside the instrument. The magnets strength is dependent upon the surface area of the metal ball it’s drawn to while removing dents. Another factor is as the tubing gets smaller in diameter there is an increase in surface radius making the tubing much stronger. So a metal ball 1/2″ in diameter does not provide enough surface area to be effective on a tube that is physically stronger. However we are working with spherical magnets to test their effectiveness on instruments like flugelhorns and trombone main tuning slides.

No. Using the MDRS™ will allow you to remove many dents not accessible without disassembling the instrument.  Not all dents can be lifted up using this system but using various tricks will allow you to do many things with less time. The system does have a high learning curve but with experience you can do very good work.  It’s as easy to do bad work as it is to do great work using this or any method.

Trouble Shooting

The only way to remove dens from under a saxophone guard is logically to get something under the guard and push up the dent. Regarding dents in or next to guard caps and strips, please take a look at our tutorials that have to do with boot jobs. We have put up step by step photos of several different operations that should be help to you. Also keep in mind that on German tuba guard caps there may be air space between the dent and the actual brass of the boot. Attempting to remove dents from areas of large guard caps can result in distorting the circumference of the bore.

This MDRS accessory does not work on every instrument depending on the thickness and tensile strength of the brass. However, on those instruments that it does work, it becomes yet another invaluable tool in your MDRS arsenal.

The A Ball Set is meant primarily for use with the 2″ RAT. You will see that if you are using a large ball, the 1.550″ tool works better than when you are using small balls – just as small balls work better when used with the strongest magnet. The larger the ball, the more pull you are going to have to it by a smaller magnet. The small the ball, the more it is going to be attracted to a larger magnet. Again, keeping in mind that MDRS results are dependent upon the thickness and tensile strength of the brass with which you are working, we’ve experienced great results using the A Ball Set in conjunction with the 2″ RAT on smaller tubing: Baritone and euphonium branches, marching brass, German tuba tuning slides, etc.

Remember, just because the MDRS does not work miraculously on every instrument, the instruments that it does work on makes it all worth while.

Send it back and we will replace it.


However, let us explain why that happened: It is crucial that all joints be tightly turned together before use. Securely screwed together, the tolling will endure whatever you can put it thought. However, unscrew the joints even by a few threads and the joint is only as strong as the 1/4-20 screw that holds them together and it is going to bend/break under stress.

Send it back for a free replacement! All MDRS tooling is unconditionally guaranteed.

Please be sure you have taken off the protective end caps.

If you have been repairing instruments for any length of time, you know that some instruments have thin hard brass, some have thick soft brass, and some have every other thickness and tensile strength of brass. The effort it takes to remove any given dent with the MDRS is completely dependent upon the thickness and strength of the brass with which you are working. Some dents evaporate like magic using the basic 1.550: N52 flat faced tool , while others resist removal even with the application of the 2″ RAT. Some of you who have been NAPBIRT members for a while will remember Don Hobbs from Eltham,. Australia. Don always invited his technician friends to come down under for a visit and told that that while they were there he would demonstrate his DHLDR (Donald Hobbs Liquid Dent Remover). ” Simply brush on and the dents disappear!” Unfortunately for us, LDR only worked at the confluence of an Australian latitude and longitude. At the present time we are unable to offer for sale either DHLDR or Elbow Grease. If you look at the examples provided here, you will see that some require more Elbow Grease than others.

The nature of removing dents in a burnishing action with a steel ball on the inside of the instrument and a powerful magnet on the outside will almost always results in scratches. The options are to leave the dents in the instrument, or take it apart and see if you can achieve better results by removing them via traditional means. There are means of reducing scratching that technicians have brought to our attention over the years, but we only ever use Mylar sheets with lubrication and do not have a problem with this method. The trick to not scratching silver/lacquer during the MDR operation is to have a large enough piece of Mylar and tape it to the body section/area of the dent. Using this method, the magnet moves over the Mylar and it is not moving over the surface during the operation.

One method that has met with success was originated by Jerry Gilbert: Use a layer or layers of chamois cloth over the end of the magnet(s), secure them in place with a heavy duty rubber band, and soak the chamois with Pledge. Another MDRS user has had some luck with the Blue assembly tape that Allied sells for that small dent that you are going after on a newer horn. Just tape over the dent, lubricate, and proceed with the operation.

You may be able to find interesting discussions on this topic (along with many other repair related topics) on the Delphi Band Instrument Repair Forum. Contact me at if you need help accessing the forum.

The cardinal rule of using the MDRS is to not attempt to remove dents from a tuba or sousaphone while in the instrument is in a vertical position (standing on the bell.) Always lay instruments in a horizontal position during dent removal operations. If the ball should come loose from the tool and fall the wrong way into the tapered tubing, it can become irrevocably lodged. If this happens to you, try the following options:

  1. Tap on the ball through the brass to dislodge it. Don’t give up on this method right away – it works a lot of the time.
  2. If option 1 does not work and you have 2 people in the shop, try using 2 of your MDRS tools by putting one tool on each side of the stuck ball to the best of your ability and with sheer brute force, pull the ball back up the tubing enough to break it loose.