Valve lapping?

Tubajug · Post by **Tubajug** » Tue Jul 05, 2011 9:45 am

I've heard of this, and seen descriptions of tubas with "hand-lapped" valves, but what is lapping? What does it do, how is it done etc? Does it only apply to piston valves? I don't recall seeing any rotary tubas with that description. Thanks from a curious mind!

Kevin Hendrick · Post by **Kevin Hendrick** » Tue Jul 05, 2011 10:22 am

Tubajug wrote:I've heard of this, and seen descriptions of tubas with "hand-lapped" valves, but what is lapping? What does it do, how is it done etc? Does it only apply to piston valves? I don't recall seeing any rotary tubas with that description. Thanks from a curious mind!

Here's a general overview of lapping as a machining operation (note the section on two-piece lapping):

http://en.wikipedia.org/wiki/Lapping

Dan Schultz · Post by **Dan Schultz** » Tue Jul 05, 2011 11:03 am

Tubajug wrote:I've heard of this, and seen descriptions of tubas with "hand-lapped" valves, but what is lapping? What does it do, how is it done etc? Does it only apply to piston valves? I don't recall seeing any rotary tubas with that description. Thanks from a curious mind!

Hand-lapping is the final fit of a piston to the casing... where a small amount of clearance is created and the micro-finishing is done.

Lapping involves the introduction of a very fine abrasive compound.

Whether valves are lapped by hand or by machine is not a selling point as far as I'm concerned but it's something that manufacturers can add to their 'bullet list' as a feature.

Rotary valves are designed with more clearance between the rotor and the casing and that fit can be obtained through precision machining without the aid of lapping.

TubaRay · Post by **TubaRay** » Tue Jul 05, 2011 11:17 am

And, I thought "lapping" was what tuba players did if they did not use a stand(or rest), such as the Baltimore Brass stand that I own.

b.williams · Post by **b.williams** » Tue Jul 05, 2011 11:34 am

TubaRay wrote:And, I thought "lapping" was what tuba players did if they did not use a stand(or rest), such as the Baltimore Brass stand that I own.

Bah-Dump-Bump!!! :

Dan Schultz · Post by **Dan Schultz** » Tue Jul 05, 2011 12:32 pm

TubaRay wrote:And, I thought "lapping" was what tuba players did if they did not use a stand(or rest), such as the Baltimore Brass stand that I own.

More like 'lapping' is what is done to get spilled beer up off the bar or floor!

SousaSaver · Post by **SousaSaver** » Fri Jul 08, 2011 8:10 am

TubaTinker wrote:
TubaRay wrote:And, I thought "lapping" was what tuba players did if they did not use a stand(or rest), such as the Baltimore Brass stand that I own.
More like 'lapping' is what is done to get spilled beer up off the bar or floor!

Dan, of course you realize that this is the technical definition that can be found in the Erick Brand manual.

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