Re: [Harp-L] slide tolerances

[Joseph Leone <3n037@xxxxxxxxxxx>]

On Dec 14, 2013, at 12:11 AM, Vern wrote:

> I have done many measurements using a depth micrometer.  I agree with Joe's numbers. More than .003" is leaky and less than .002" is insufficient clearance. I have measured clearances on 270s up to .007".  
> 
> Hohner does a poor job of controlling slide clearance. They bend up the flanges of the U-channel and then use whatever clearances result.  In my opinion, they need another operation to accurately machine the height of the flanges.  I made some little jigs to perform this operation that I sent to some of the better-known technicians.  Inquire if your technician can scrape your U-channel.

..... I have one of Vern's slide U-chanels on my main performance chromatic. It is around .002 and works perfectly. The chromo is tight and bright. Good job Vern. 

Another thing that can be done is to scrape the upper edges of a slide on a 45 degree angle. The edges as supplied have sharp edges. That's ok on the bottom, BUT because the U-channels are 'pressed' into shape, their inside turns in the brass are (naturally) rounded. So sharp edges on the TOPS of the slides can rub or at worst bind in these rounded corners if the U-channel is shaved down. 
> 
> Clearance is more critical in short-stroke slides in straight-tuned instruments such as the 270.  This is because the paths through the slide from hole to hole are much shorter than they are in the long-stroke slides of cross-tuned instruments such as a CX12 or 64.
> 
> To check the hole-to-hole leakage, remove the covers, stand in front of a mirror and blow one hole while blocking the two adjacent holes.  Lifting of the adjacent valves will indicate the amount of leakage through the slide. 
> 
> Of all the things that you can do to improve the performance of a chromatic, reducing excess clearance is the most effective by a wide margin.
> 
> Vern
> 
> On Dec 13, 2013, at 3:28 PM, Joseph Leone <3n037@xxxxxxxxxxx> wrote:
> 
>> Generally they are mostly .003" (3 one thousandths)...but it's done in 'metric measurements'.. This covers most players. Pros, OR people who will keep their slides clean, can get away with .002. I'm sure that people have measured. Going below .002 is just asking for grief. 
>> smokey-joe
>> 
>> On Dec 13, 2013, at 2:28 PM, Music Cal wrote:
>> 
>>> Does anybody know what the gap size is between slide and slide channel for
>>> various chromatics? Have you done any measurements?
>>> 
>>> MusiCal
>> 
>> 
> 
>