Friday, November 8, 2013

How to fix a cup in a glued up panel – or how I wasted a week…

So where I last left off; I had returned from WIA to find that my Top for the EMC I had glued up before I left now how a 3/16” cup in it.  My first thought was I need to rip it apart and re-glue it.  Fortunately I made a design change and actually needed to reduce the tops thickness by 1/8” or so.  So then I thought why not take it a cabinet shop with a wider drum sander than I have to thickness it and sand the cup out.  But I was then worried that the feed rollers would just press the cup out as it sanded and I would just be left with a thinner top that still had the cup.  So off to my books and the internet for some “old fashion remedies”… 

The first solution I found was to wet the convex side and let it dry under weights.

No Luck

The second solution was to wet the concave side and let dry stickered. (sorry no pics)  Some Luck – after three rounds of this I was able to reduce the cup by a 1/16”.  In fact, while the top was wet, it actually cupped in the opposite direction but then it dried with pretty much the original cup still in it.

The Third solution was to use a heat gun on the convex side to shrink the fibers and reduce the cup. 

No Luck

The fourth solution was to cut kerfs in the underside and epoxy a long strip in the kerf. I then let it cure while clamped to a flat service.

No Luck – It did dry flat, but then cupped as soon as the clamps where removed.

The correct solution -  rip it, thickness it and re-glue it.  

Results – prefect.

So, while wasting a week dealing with this I did learn (one more time) that there are no easy solutions and you’re first thought is sometimes the best one.

Thanks for stopping by,


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