1978 Besson New Standard -- Valve Guide Wear / Noise

[Markmc611]

Re-doing the valve guide tabs (aka "Tacquets") on an older Besson is absolutely NOT a doit yourself type of repair for most of us. The correct part is BBH9172 at http://www.dawkes.co.uk/accessories/...+-bbh9172.html and is very cheap. But it requires filing and fitting to install these as they come oversize in order to be able to adjust for wear and manufacturing differences between horns (or even individual valves on the same horn). Further, there are now Delrin plastic tacquets available through repair supply folks. These can quiet down the valve action dramatically. I had these installed on my old Conn Connstellation and valve noise is a thing of the past.

Doug

Doug, that link appears to be dead. So, I googled the part number and found it at http://www.dawkes.co.uk/b%26h%5Ebess...?catno=bbh9172 .

I'm looking to find a set of delrin guides for my '75 Besson. Question, are the threads on these guides SAE 3-48?

If not, is it possible to machine the valve piston to accept a SAE 3-48 thread?

[ghmerrill]

I don't know what the thread size is on those pistons. I bet if you shoot an email to Dan Schultz (http://www.thevillagetinker.com/) he could tell you. Otherwise it's tricky since you have to be VERY careful trying different size screws in it because the brass is soft.

It is straightforward to re-tap the pistons for a different thread -- assuming that thread is of larger (even slightly larger) diameter. All this takes is getting (a) the correct tap (usually about $5 or so), and (b) the correct drill to drill out the hole for that tap (usually a couple of bucks or so). Any repair tech should already have these, and it takes only a few minutes per piston.

I did this myself on my old Buescher tuba, following Dan's suggestion so that I could use 3mm nylon "cheesehead" screws to make the guides. I did use a drill press to drill out the holes in order to be absolutely sure they remained square with the piston, but this may have been excessive. And then I was very careful and slow about re-tapping in order to avoid any shavings from falling into the hole (so backing the tap out frequently). But it really only takes a few moments. It worked great. There is an advantage to this approach in that you will have a supply of replacement screws, and this is quite handy since the plastic guides wear faster than metal ones. And you don't want to be looking around for esoteric and hard to find parts again in another few years.

If you do decide to go this way (via repair tech or by yourself), I've still got about 95 of those 3mm cheesehead screws left over , and would be happy to mail you a bunch of them. It took much longer to cut them down to fit the guide slots than to drill/tap the holes. By the time I'd finished the third one I'd developed the right touch. Sanding is not particularly efficient, and an Xacto knife or (better for me) razor blade is the way to go. Then it's just trial and error.

One thing you have to watch out for is that if those valve guides have been in there for a long time, you may discover that the top of the guide slot has gotten peened closed a bit and the old guide has become worn to fit that profile. So you may need to open up just the very top of the guide channel with a Swiss file so that the new guide will fit into the slot and run freely. It took me a few minutes, and one wasted screw, to figure out this was case on my horn.

[Markmc611]

I did this myself on my old Buescher tuba, following Dan's suggestion so that I could use 3mm nylon "cheesehead" screws to make the guides.......

If you do decide to go this way (via repair tech or by yourself), I've still got about 95 of those 3mm cheesehead screws left over , and would be happy to mail you a bunch of them. It took much longer to cut them down to fit the guide slots than to drill/tap the holes. By the time I'd finished the third one I'd developed the right touch. Sanding is not particularly efficient, and an Xacto knife or (better for me) razor blade is the way to go. Then it's just trial and error.

One thing you have to watch out for is that if those valve guides have been in there for a long time, you may discover that the top of the guide slot has gotten peened closed a bit and the old guide has become worn to fit that profile. So you may need to open up just the very top of the guide channel with a Swiss file so that the new guide will fit into the slot and run freely. It took me a few minutes, and one wasted screw, to figure out this was case on my horn.

Ideally, this is a project I'd like to work on this weekend. Are those cheesehead screws available at "what passes for a hardware store", these days? My other thought would be to get a set of Willson old style guides, and slap them in there. Thanks in advance, for any other thoughts, or suggestions.