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blokewashers

bloke wrote:Measuring a piston valved instrument for the correct thickness washers/felts isn't rocket science, but even trying to describe it (without picture/video) becomes hopelessly wordy/technical.

I use two tools: a gauge and calipers

Rarely, I might additionally use a second gauge.

The gauge indicates the height from the top of a key port in the casing to the top of the casing. The calipers measure three or four things that must be considered.

More than this (again) the description of the (albeit relatively simple) procedure becomes goobledegoop.

The key here is that the basic requirement is to have the horn in question 'on the bench'.

There are a few special matters with the Conn short action pistons as found in the 2XJ and 20K/22K instruments. The special valve guides have been mentioned. For some odd reason this system also was found in the Dutch Schenkelaars instruments quite common her 40 or 50 years ago.

And then there are the oval ports, which are geometrical the deviation allowing for the short stroke. Any misalignment of these ports will block a larger percentage of the port area, than would the same misalignment with a normal piston. Hence exact alignment is critical with these valves.

Klaus