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Cracked Shank

kevgermany

ex Landrover Nut
Subscriber
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21,947
Any ideas on how to repair/seal a cracked mouthpiece shank? Mouthpiece is an old cream plastic brilhart, although the shank has been banded, the crack is leaking enough to make the lower notes unstable (and I thought it was me...).
 

c9off

Senior Member
Messages
604
You carefully dremel a channel, both inside & out, preferably with an undercut. A mix of epoxy (much more than you intend to use to avoid mix ratio issues) is then mixed with an aggregate, in this case matching stone powder (you know the stuff, its at the back of the cupboard).

resin in separate applications, on the inside I would apply tape over the wet resin to maintain an accurate curvature.. outer you could do the same but would prefer to lay proud then sand & polish to a finish.

Or send it to me & I'll do it - foc..

Dont expect cyno to wick in effectively by the way.

good luck either way
 

jonf

Well-Known Member
Messages
3,680
You could probably manage to get away with just using WaterWeld if you don't have any stone powder in a matching colour. It's a fairly creamy sort of colour, sets rock hard to pretty much anything, and is also certified as safe for use on drinking water containers. I know it's the shank end, but you'll probably feel better with something you are certain is food safe. I've used it to good effect to replace missing bite plates on a couple of mouthpieces.

I'm sure a practical chap like you can make a reasonable job of it.

Jon
 

kevgermany

ex Landrover Nut
Subscriber
Messages
21,947
Thanks, C9off. I guess a little round hole at the end to the crack, suitably filled, will help to stop it spreading further. Your method sounds perfect, although stone dust may have to give way to Jon's suggestion.

Jon, thanks, will see if I can find waterweld here. Hopefully it has the same name....
 

kevgermany

ex Landrover Nut
Subscriber
Messages
21,947
Update

Waterweld finally arrived yesterday.

I've completed the repair using waterweld as suggested I carved the crack out and filled it with plenty of waterweld. I did this in two stages, inside, then outside. When I cut back for the outside, I made sure that I went all the way through to the new waterweld applied to the inside. I also made sure teh original carck was completely cut out and a rounded end given to the hole, so that there's no more crack present to work it's way further up the shank in future. Wasted a bit of waterweld, but as warned, better too much than too little. Finishing it to size was straightforward. And the mouthpiece now plays nicely.

Some observations for guys thinking of doing the same thing:

Waterweld is easy to work, but clogs files and abrasives very quickly. Have a metal brush handy for the file, and don't let it get too clogged, otherwsie it's difficult to clean.

I used the dremel with a grinding bit to carefully cut back the excess waterweld. Worked fine, but in a couple of places the waterweld flaked off as it got thin. It seems to have stuck well, so I don't think there's a problem. Just go easy on the finishing.

For final finishing inside the shank I used wet & dry wrapped on a piece of hardwood dowel, slightly smaller diameter than the shank id. Worked well & I was able to get a pretty close match to the original roundness. To avoid sanding where I didn't want to, I just used a strip of wet & dry lengthwise, not wrapped all around the dowel.

The waterweld wasn't a bad colour match but is slightly porous, so picks up dirt/colour easily.

Impossible to cut/sand it back without sanding the shank as well, even using the finest wet & dry I can get (1000 grit) the surface is matt and like the Waterweld, picks up colour/dirt easily. I found this when I polished the band back with metal polish. It might polish up with the stuff that you get for restoring CDs, but it'd take a while.

Net result is that I'll be painting the shank with modelling paint, a couple of coats will cover the colour difference and protect the matt areas from ingrained dirt.

Thanks again to C9off and JonF for the super suggestions!
 
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