A ferrule with a .312 bore and .308 tenon would give you a .099 wall on the ferrule with a perfect interference fit for epoxy gap fill.
ferruel keeps breaking
- Thread starter 3cfan
- Start date
Perfect interference ?
You mean gap-filled loose fit . How are the vertical grooves even helping the cause ?
That would be a bottom gap waiting to happen b/c there is no mechanical bond .
Epoxy SHRINKS eventually. Wood moves .
Might as well keep the tenon at .312 and bore the ferrule at .312 and score the walls with a 5/16 tap. At least you have a little of epoxy rings around the ferrule.
Better yet keep the bottom of the tenon ( about 1/8 ) at .314. At least you get a press fit down there.
Actually the bottom of the threads would be closer to .380.
The hole is still around .330'sh.
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The only place the threaded hole will be as thin walled as the through hole is in the bottom of the threads. All the mass in between thread crests = more meat than if the hole were straight 3/8.
That doesn't matter, anyway. What matters is that the ferrule keeps cracking because there's no cap, not because it's threaded. A .125" cap at the end would eliminate the issue.
That doesn't matter, anyway. What matters is that the ferrule keeps cracking because there's no cap, not because it's threaded. A .125" cap at the end would eliminate the issue.
OK......... I agree .... a ferrule installed that short and that thin should have a cap............... I would not thread it...........
KIm
Bob-O-Rama
Registered
Note the trapped air pocket - both parts need to be properly coated and mated together slowly to exclude air bubbles. Sometimes this happens when the glue absorbs into the shaft. The missing volume of glue forms a void. In which case you pre-impregnate, and let it cure, so that this does not occur. Its also seems not properly faced, looks like a bandsaw or 60 grit sandpaper rather than a lathe. If you face the ferrule with a bazillion scratches, each scratch can be the seed of a running crack, no matter the material used. Note the orientation of the marks in the wood, and the location / orientation of the bottom crack. And, of course the material used, coarse reinforcing linen and cleavage plane oriented to ensure failure as the tip mushrooms under impact.
Looks like they're just scores b/c the ferrule threads do not match.
I have to agree with this one after looking a little closer. To me it looks like someone used some threaded stock and filled the threads with the adhesive. Or thought that would act as the keys to hold it on. A little extra stroke to get a few extra rails on a billiard table and disaster.