Andrew's blog

Harmonica Repair Basics

Rockin Ron told me that he gets quite a few technical support questions about replacement reed plates. The harmonica looks like a simple instrument but once you have taken it apart for the first time, you realize how important all the little details can be!

Here's a video about the basics of installing new reed plates into your favorite harp:

The F tool™

The F Tool™ is now available in the Tools section

A well-playing harp has a solid connection to the vocal tract. A big part of what makes it is easy to play, sound nice and fat is that it's airtight.

If it leaks air, the connection between your vocal tract and the instrument is weakened and the harp feels stiff. The tone is also weaker.

The good news is air leaks are fixable! In fact, that's the fundamental step in improving a harmonica. If you skip this step, you will usually end up working against yourself further down the line.

The detailed instuctions on How to use the F Tool are here.

Wonderful Cacaphony

Can you tune a bunch of diatonic harmonicas with precision in the same room at the same time?

Of course you can!

This is a moment captured during a harmonica repair workshop in Kingston, Ontario on 2015/05/16. The was the first time each of the participants used the French Tuner and I was impressed at how well they could tune a harp! Great job, guys!


I just bought a second CNC mill. It's bigger and faster than my first one. A second machine will improve my productivity and save time. It will also allow for redundancy. Routine maintenance won't affect my production time.

I bought it in the USA and crossed the border to pick it up the other day. I had to describe what I was bringing back to Canada to three different Border Services people and it's not an easy tool to describe.

Not being able to quite explain it in ten words or less, I said: "It's kind of like a 3-D printer".

Each one had the exact same reaction: "Really? Ahh! That's so cool!" they said and nodded...

I use my CNC mills to make combs, tools and a few other interesting tidbits I would never have conceived just a few years ago. Computer aided design (CAD) and computer aided manufacturing (CAM) is so accessible these days. Oscar Goldman was right! "We have the technology."

Event: Harmonica Retreat Workshop at Shared Harvest Community Farm

Wonderful organic food and world-class harmonica instruction are happening in Dunneville Ontario on the weekend of June 26th, 2015. Don't miss it!

Carlos Del Junco

Ronnie Shellist

Roly Platt

Workshops will include 3 chord song structure, comping vibrato and tone, using transcribe software to break down songs, demystify licks and learn your favourite runs, playing effectively and simply, 1st 2nd and 3rd position playing, tunings, rhythm playing, playing melodically, overblows, sitting in with a band, techniques, do's and dont's, harmonica maintenance (with Andrew Zajac) and group sessions with all the instructors.

Don't miss out on this opportunity to learn and play with three world class harmonica players/teachers, enjoy amazing food and have a true blues experience under the willows by the Grand River.


To register for the Harmonica Workshop please send an email to Also include your name, address, phone number and email address.

Dynamic Range

Here's a description of a harmonica's dynamic range and some of the things that improve or worsen it.

Warning, this is a pretty boring video.

Producing CNC milled combs revealed!

I design my combs myself and produce them using my CNC mill. Here's a breakdown of the process.

The combs are cut. Water is sprayed on the surface as the mill works to cool the bit as it cuts. Keeping the temperature down helps keep the bit sharp and prevents the finished comb from giving off a strong smell. Fresh off the mill, the combs look a little rough....

After a quick rinse....

Each comb is held in place with support bridges. Here, I have cut them free.

Then wash away the debris.

The rough combs need to be sanded polished and flattened. I first start working on the outer edges and tips of the tines.

Here the outer edges and tines are smooth.

Next, I flatten the top and bottom sides. I check for flatness using a reference. This comb is not flat and needs to be fixed.

After a little work, it's flat.

At this point, the combs are starting to look nice.

Next, I round off every edge. The front (tines, viewed from the side) is rounded.

...and the corners...

Next, I painstakingly work on the inside of every tine. I make sure each one is shaped for comfort.

These tines are comfortable on your tongue.

I start the process of lacquering the tips of the tines. I apply many thin coats instead of only a few thick coats. I do this to ensure the lacquer doesn't chip or crack. My aim is that they last a lifetime.

This is after one coat.

After several coats...

If it's dry and it looks wet, it's done!

Next, I polish the sides and back of the comb. The last step is to flatten the comb one last time to ensure it's going to deliver peak performance.

Combs get wrapped up immediately and are ready to be shipped.

Mysterious embossing instructions - Can you see the light?

I offered some Mysterious Embossing Instructions which included a clue you can download and print out.

This video explains the clue I gave, my reason for offering it in this way and a demonstration of how I use indirect light and a three-dimensional view to make quick and effective work of embossing harmonica slots.

With this method, you get benefits similar to using a microscope and a light-table but avoid the respective disadvantages and limitations of those devices.

Mysterious embossing instructions

Embossing decrease the space between the reed and the edges of the slot. With higher tolerances can come better performance - the harmonica responds better and plays louder.

The thing about embossing is that so much can go wrong. Fixing the damage can take more time than it takes to do the actual work of embossing the slots.

So how to you "walk the line" to get maximum benefit without creating problems for yourself?

Some folks advocate special tools. Some use a light table. Others use a microscope - sometimes.

All those things can work well. But every method has its disadvantages.

For example, a fast-acting tool can overshoot the mark causing you to work against yourself. A light table only shows you two dimensions and as the reed passes through the slot in three dimensions, you can be left confused as to what you are seeing. A microscope can be overkill - you may not even need one if you have good eyesight. You certainly don't need to use magnification to do most of the work - if anything, you would want to shorten your view of the slot instead of zooming into one segment. But if you are over 40 years of age, using some form of magnification is probably good idea.

Let me share a secret with you: You can get top-level results using simple methods that don't rely on fancy technology.


I'm not telling you. I don't make a habit of keeping secrets, but this is something I have never shared before in public.

I am happy to show folks the basics of how to tweak harmonicas and I have a strong preference for some methods, but there are may ways to get a task done. You don't need to know this secret to do a great job. This method's advantage is that it makes things easier and saves lots of time if you do it correctly.

Again, I'm not going to tell you what it is. I will, however, give you a clue.

Here it is. Print it out. (It's a way of looking at embossing.)

Contact me if you think you have it figured out. I'll let you know whether you are hot or cold. I'll add the most interesting responses to this page as they come in.

Good luck and don't hesitate to contact me!

2014/11/24 - Stephen C. described the way he holds the reed plate to "get a pretty good sense of what's going on in the space between the reed and the plate" and he's very close to what I describe!

2014/12/25 - Jaime G. wrote about "aligning tip edge with edge under rivet (to emboss) with a secure and efficient method."

EDIT: The mystery is over! My explanation can be found here!

"Where can I get that engraver?"

I get asked about the blue engraver you see in my YouTube videos. I use it for tuning.

It's from a local store and they no longer sell that model. I bought a few of them when they were clearing them out. They seem to last forever.

From the product description:

Hold the engraver as a pen and apply a minimum amount of pressure. Do not apply excessive force when engraving, as a higher speed will result in better engraving. Free speed: 11,000 to 12,000 RPM.

Here is the new model:

The newer models come with a smaller tip. I like the bigger tip - it's gentler and I can get really close to the side of the reed and not have to worry I am going to cut through the reed. What I do looks a lot more like chamfering once I am done.

Here are the two types of tips you can easily find on Ebay:

With the big gentle tip, I feel I can take off a lot of brass or stainless steel without distorting the reed.

One thing about some engravers is that they can have a little or a lot of run-out.

What is run-out? It's an inaccuracy of rotating mechanical systems, specifically that the tool or shaft does not rotate exactly in line with the main axis.

A lot of run-out will make the tip wobbly and difficult to use. You will distort the reed using such an engraver.

Hold the tip up to the light and watch it spin. If it stays straight, you've got a good one.

If the tip wobbles, I suggest you find a better engraver. Many cheap engravers made in China can have a lot of run-out while some will have almost none. I bought five of them for $2 each and threw four away.

It took me a while to get used to files. Early on, I wrecked reeds, bent them out of shape and overshot the mark using files. A good quality file helps. I found it a lot easier to use the diamond-tip engraver. (Nowadays, I prefer using a Grobet file). I suppose there are many ways to get the job done!

Use any method that brings you success!


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