Does anyone have any suggestions for how to go about doing this on a metal
mouthpiece?

I've a metal piece I'd like to open, where opening the tip is not feasible.
I read Mojo's recent post about doing this on a HR Meyer 4M, but doing it on
a metal piece will be more difficult.

While I can see I need to apply pressure to the heel of the mouthpiece, I'm
uneasy about getting the table flat again accurately, and not taking off
metal at the break point, and looking for a way to do this as accurately as
possible.

I've considered gluing a thin steel metal shim to the piece's facing at the
break-point as a way of doing this. The shim and the heel of the facing
would be worn away, and I would be able to see the new flat extend gradually
towards the break-point.

Barry

Before you start, measure the thickness of the mouthpiece body across the
table heel with calipers or a micrometer.  You can do a detailed
calculation on how much this measurement needs to get smaller to get the
tip opening change you want.  It is typically 3-3.5 times the tip change. 
So this method can not be used for large tip opening changes.

You can start by leaning hard on the heel and creating a flat spot there. 
You can watch it grow in length as you proceed.  It will help to use
coarser paper than you would normally use for rail work.  I usually start
with 220.  

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Thanks, Keith; your advice is much appreciated

Barry

> Before you start, measure the thickness of the mouthpiece body across the
> table heel with calipers or a micrometer.  You can do a detailed
> calculation on how much this measurement needs to get smaller to get the
> tip opening change you want.  It is typically 3-3.5 times the tip change.
> So this method can not be used for large tip opening changes.
>
> You can start by leaning hard on the heel and creating a flat spot there.
> You can watch it grow in length as you proceed.  It will help to use
> coarser paper than you would normally use for rail work.  I usually start
> with 220.  

> Before you start, measure the thickness of the mouthpiece body across the
> table heel with calipers or a micrometer.  You can do a detailed
> calculation on how much this measurement needs to get smaller to get the
> tip opening change you want.  It is typically 3-3.5 times the tip change.
> So this method can not be used for large tip opening changes.
>
> You can start by leaning hard on the heel and creating a flat spot there.
> You can watch it grow in length as you proceed.  It will help to use
> coarser paper than you would normally use for rail work.  I usually start
> with 220.
>

Thanks again Keith for the tips.

I did a test run on the afore-mentioned inexpensive Chinese metal
mouthpiece, before going on to adjust the metal mouthpiece that really
mattered.

I used 220 paper as you suggested for the major cutting.

I found that I could control the relative amount taken off the table at the
heel vs. closer to the break by exactly where I gripped the mouthpiece - and
that I could do some fine incremental adjustments by gripping it slightly
further in front of the heel.

In addition to sliding it lengthwise on the paper, I also tried sliding the
mouthpiece sideways on the paper, and turning it to face the other way with
each stroke, in order to cancel out possible pressure inequalities in my
grip that might cause the table to get slanted. This seemed to work.

Bottom line - success!  I was able to achieve *very* satisfactory results
rehabilitating my old #5 Link. (Which already had some work done to the tip,
and not much more could be done there).

Barry