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Gronitz PCK first valve slide problems

PostPosted: Mon Mar 20, 2017 1:22 pm
by RobSol87
Good Afternoon Tubenetters!

I'm located in Jacksonville, FL and I'm having trouble with a first valve slide on my PCK not pulling freely. I've tried a myriad of slide lubricants, valve oils, and trombone slide lubricants to try and help and it would seem that I need to get the slide lathed. Does anyone know of someone within a few hours drive that would be able to help me with this issue? I've heard that there's someone in Orlando that would be able to help, I'm just not comfortable with anyone in Jacksonville or the immediate surrounding areas with this.

Thanks in advance,
Rob Solomon

Re: Gronitz PCK first valve slide problems

PostPosted: Mon Mar 20, 2017 5:18 pm
by DouglasJB
How is the alignment?

Re: Gronitz PCK first valve slide problems

PostPosted: Mon Mar 20, 2017 6:21 pm
by PaulMaybery
Usually this is a combination of allignment and getting the slides lapped so they are a bit reduced in diameter and in the process polished smooth.
Then most slippery things can do their job.
The lapping is relatively simple but the alignment can be anything from reheating some joints and letting them snap back into place (if you're lucky) to having to actually move or readjust some of the braces. Often times, the crook does not match the width of the two slides. Even a couple of MM can cause it to bind. I had this on a brand new horn. The crook was removed, filled with pitch, slightly re-bent to the proper shape and then refitted. It now works perfect. A caveat about lapping. If too much is removed the slide will leak. Yes you might get it to move smoother, but at a serious loss to compression. Best bet is to find an experienced and highly skilled technician. They are like doctors, that is, some are much more skilled than others.

Re: Gronitz PCK first valve slide problems

PostPosted: Mon Mar 20, 2017 6:53 pm
by ValveSlide
In general, Gronitz tubas have a extremely well fitted slides. They don't come sloppy, but rather it's left up to the player to decide which slides they want move on the fly. They typically only require some light lapping and buffing to move well unless something/someone has done something to change this.

With some other brands loose slides with mediocre alignment (faster and cheaper to make) have become the norm.

No torch, lathe or sandpaper should be needed.

Re: Gronitz PCK first valve slide problems

PostPosted: Mon Mar 20, 2017 7:49 pm
by bloke
Run - do not walk - away from a guy with sandpaper or a tubing expander...UNLESS (after a great deal of measuring and inspection) they point to a SPOT that needs to be addressed with one of those, and explains WHY.

If the first thing that some one grabs is calipers, you might be in the right repair shop.

===========================================

assumption: The INDIVIDUAL pairs of tubes work nicely, but BOTH PAIRS TOGETHER do NOT work nicely...

...Is this the case?

You're nowhere near ValveSlide, but - if you were - I'd send you his way.

Re: Gronitz PCK first valve slide problems

PostPosted: Wed Mar 22, 2017 10:35 am
by RobSol87
Thanks for the input everyone! I purchased the horn from Gronitz and not through a private seller so I'm comfortable saying the slide is almost certainly aligned properly. It's just not pulling as easily as I would like. The one person down in Orlando I've spoken with mentioned sand paper so I'm back to square one.

Re: Gronitz PCK first valve slide problems

PostPosted: Wed Mar 22, 2017 11:54 am
by bloke
RobSol87 wrote:Thanks for the input everyone! I purchased the horn from Gronitz and not through a private seller so I'm comfortable saying the slide is almost certainly aligned properly. It's just not pulling as easily as I would like. The one person down in Orlando I've spoken with mentioned sand paper so I'm back to square one.


If the tube pairs move quickly INDIVIDUALLY, you do not need to have the inside slide tubes sanded/buffed.
If the tube pairs are tight INDIVIDUALLY, you possibly could benefit from some very cautious sanding/buffing...

...BUT alignment (if poor) must always be addressed FIRST, or nothing will be accomplished of benefit.

600 grit paper is coarse enough to remove a measurable amount of material, but fine enough to not be quickly ruinous.
250 grit works much more quickly, but should only be used by someone you absolutely trust and/or has impeccable repair credentials.

Even marks put into the exterior of inside slide tubes by 600 grit paper need to be polished out to remove friction.
1500-then-2000 grit paper (particularly when combined with valve oil) will come close to imitating a subsequent buffing job.

Re: Gronitz PCK first valve slide problems

PostPosted: Wed Mar 22, 2017 11:56 am
by bort
Who's top dog in tuba repair up in Atlanta?