Topic: "Screech Hole" on bocal for high notes

I have been wanting to modify one of my seldom used bocals with the so called "screech hole" installed near the tip.  Here are the dimensions as I have found them: .002" hole placed approx. 18mm for the tip of the bocal.  Pressumably one is to use a .002" or so drill bit to accomplish this, but I have had no luck at the local hardware stores finding anything close to this size.  Further searching on-line reveals such a plethora of drill bits I dont even know which type of drill bit should be used.  MY questions are as follows:
Is just a simple hole sufficiant, or does it need to be elevated similar to the whisper key hole?
Are these demensions still current, or have the generally accepted measurments changed?
If using a drill bit is okay, any recomondations for brand, and type?

While on this subject, anyone wich to describe advantages disadvantages to playing with this hole installed?

Thank you for the helpfull replies in advance.


Re: "Screech Hole" on bocal for high notes

Hi Justin

I use that sort of bocal every day. Yes your measurements on the hole is OK.
The hole should be 25 mm from the reed end of the bocal and pointing upwards.
I use a plastic cap that I can slide over the hole when you dont need it.

If your seldom used bocal is thin walled the result will be even better.

Good luck

Last edited by RobertR (2005-02-06 23:59:50)

Robert Roennes


Re: "Screech Hole" on bocal for high notes

Hello Justin,

You're never going to find a 0.002" drill.  Besides, that's the wrong size.  I think you're off by a decimal point.  You should be able to find a set of #61-#80 drills.  Standard number drill sets stop at #60.  The smaller set ranges from 0.039" to 0.0135".  You may need a special chuck to hold these very small sizes. 

There have been several players that have experimented with this trick.  Arthur Grossman is probably the foremost among them in working on the details.  He posted information about his experiences on the doublereed-L list on 11/13/96.  At that time, he was placing the hole at 11/16" from the end of the bocal, which he noted was closer to the end than the 3/4" mentioned by Bob Barris.  Other experimenters have worked with a placement of 1" (25mm) from the tip.  As for the hole size, he tried hole sizes of 0.020", 0.025" and 0.030" and concluded that he preferred the .030" best. 

None of this is very critical.  The simplest specifications for the hole is "as small as you can get and about one inch from the end of the bocal."  In fact, a bocal with a slightly leaking split seam can often accomplish the same trick. 

Arthur also created an interesting mechanism that would operate this vent hole.  The keywork was entirely mounted on the bocal and was operated by opening the high D key.  That's more than most of us will ever be interested in doing.  Usually, a bit of tape to close the vent is sufficient.  That small of a hole is not going to make a lot of difference in the instrument's performance. 

Chip Owen


Re: "Screech Hole" on bocal for high notes

Thank You Robert and Chip for your replies.  This is precisely why I posted this- I found these measurements in an IDRS article about the device Mr. Grossman had made, and perhaps it was just printed with an incorrect decimal point.  After holding the smallest drill bit I could find (~.06"),  which was quite small, I did have a large doubt whether a .002" could be the correct size.  Incidentally, I did find a drill bit manufacturer who does produce a bit down to .002" and even smaller, however they were quite expensive, and only came in large packs (presumably they break easily?). Now to "swiss-cheese" my bocal......

Thank you again,


Re: "Screech Hole" on bocal for high notes

Prof. Grossman's article "measurements for hole in bassoon bocal " from the IDRS-L Archive$/www.idrs/registration/emailarchive1.taf

Subject: Re: measurements for hole in bassoon bocal (high register)

From: Arthur Grossman <artg@U.WASHINGTON.EDU>

Date: 09/06/2001

Time: 13:11:33

You should start with .020" and if you need to, gradually increase the size up to a max. of .030" I usually find that about .025 to.027 works best on most bocals and reed combinations, but you really do have try it out at each stage. Ideally you want the hole as close to the tip of the bocal as possible, but clearly, there is a limit. First by the reed itself and how far your reeds go onto the bocal. Then IF you add the key, it needs to be even farther. Max. distance should be 18mm. Sorry for mixing inches and mm. but my drills are inch drills, otherwise I find metric easier.  Arthur Grossman Bassoon, Heckelphone and Contrabassoon School of Music Box 353450 University of Washington Seattle, WA 98195-3450  On Thu, 6 Sep 2001, Susan Hess wrote:  > Does anyone know the exact measurements to drill a hole in a bocal to > improve extreme high register response? > > _______________ > Susan Hess, D.M.A. > Assistant Director /Assistant Professor of Bassoon > Lionel Hampton School of Music > University of Idaho > Moscow, ID 83844-4015 > 208-885-6232 208-885-7254 (fax) > > >

Yoshi Ishikawa
Professor of Bassoon, University of Colorado at Boulder, College of Music
Editor, IDRS OnLine Publications

Re: "Screech Hole" on bocal for high notes

This is the article I found that had the decimal place discrepancy, it also has a picture of the device Mr. Grossman installed to open and close the hole: