European shank and Morse shank explained

Hello,
I am writing this in the hope that someone can help me understand the difference between a mouthpiece with a European shank and one with a Morse shank.

I have two horns. A 50 year old Alexander 103 and an Atkinson I purchased about five years ago. By way of comparison, a mouthpiece that fits the Alexander (Josef Klier or an Alexander) placed in the Atkinson only goes in a little way and wobbles. A mouthpiece that fits the Atkinson placed in the Alexander falls in nearly to the point where the mouthpiece begins to widen to the cup. Based on this observation, I assumed (I know, never assume) that the European shank was slightly larger in circumference.

About a year ago, I purchased two mouthpieces from the same manufacturer. They were different models of the same line of mouthpieces – one with a European shank and one with a Morse shank. After they arrived, I tried them out on the respective horns. I realized that I put them with the wrong horn. They looked like they fit the same. I drew a pencil line on each mouthpiece where it fit into the leadpipe. When I put them side by side, the pencil limes matched. I got a set of calipers and measured each mouthpiece. On both mouthpieces, I measured 7.50 mm at the open end of the shank, 8.25 mm at the line I drew for the Atkinson, and 8.62 mm at the line I drew for the Alexander. It would seem to me that there is no differences between the mouthpieces.

I wrote to the manufacturer and asked if it was possible that I had been sent two mouthpieces with a Morse shank. The following was their reply: “The difference in shank size between the Euro and the Morse is not great, the main difference is in the rate of taper. It leads to a small difference in the way the mouthpiece fits in the receiver. A Josef Klier or an Alexander mouthpiece not only has a European taper, but the shank size itself is larger. The receiver on Alexander horns varies widely and wildly depending on the year of manufacture. I would advise you to go with what give you the best results.”
I was still confused, but they aren’t answering any more questions.

Hi Michael,

All American and most European mouthpieces have what's called a Zero Morse taper. Morse tapers are used in American machinery. The different Morse tapers vary slightly but all grow about 5/8 inch per foot. This works out to an angle a little less than 1.5 degrees. Most mouthpiece makers are still sticking quite closely to Vincent Bach's shank dimensions, which call for a tip diameter of .294" and an insertion depth of .625" into a standard receiver that measures .325" at the end. (This is actually incorrect as the insertion depth is actually .595". The difference is insignificant.) We use a .295" measurement at the tip. Most modern horns measure about .330 at the receiver so the mouthpiece goes in a little farther.

Alexanders and some other European instruments (fewer every year) use an Alexander taper shank. It measures .302" at the tip but the angle is less-1 degree. Because the tip is larger and the angle less Alexander shank mouthpieces often stick out farther and wobble in American horns.

It's important to remember that there is no fixed relationship between the end of a horn mouthpipe and the venturi. The only thing that changes when the mouthpiece fits further in or out is the volume of the mouthpiece-mouthpipe system, and thus the response and feel of the horn. Intonation is not affected. Most horns have malleable mouthpiece receivers so you can (and should) seat either shank with a light twist. Some modern makers are now using a machined receiver, like a trumpet receiver, and supply bits with both Morse and Alex tapers.

So, to sum up: Yes there are differences in the receivers but there is no "right" answer of easy was to predict what's going to work. I agree with the maker who told you to "go with what give you the best results".