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cracked my back
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10122&t=28194
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Author:  devincox [ Tue Jul 13, 2010 8:31 am ]
Post subject:  cracked my back

Last night while I was using my scroll saw to rough out the back, the (new) scroll saw blade grabbed and cracked the back in two places. My question is, is it worth repairing? The cracks are barely visible until I apply pressure to the back. They run with the grain about 12" long. The wood is primavera.


http://www.devincox.com/images/backcrack.jpg
Thanks,
Devin

Author:  Joe Sustaire [ Tue Jul 13, 2010 12:47 pm ]
Post subject:  Re: cracked my back

Devin you can probably save the top by using water thin CA, (super-glue). Just make sure the crack is tight, (might have to use some tape to pull it tight) and flood with the thin CA, it wicks into the crack. Let dry or hit it with some accelerent and then sand. I know those lucky enough to build with brazilian rosewood have to get pretty good at dealing with hidden cracks.

Joe

Author:  devincox [ Tue Jul 13, 2010 3:37 pm ]
Post subject:  Re: cracked my back

Thanks Joe. Excellent news. I will pick up some thin CA tonight and give it a try.

Devin

Author:  Bob Shanklin [ Tue Jul 13, 2010 10:22 pm ]
Post subject:  Re: cracked my back

Devin

Switch to the spiral cut scroll-saw blades. 46 TPI, and cut on the up and down stroke. Only blade I use in my Dewalt scroll saw for cutting backs or tops.

Bob

Author:  devincox [ Wed Jul 14, 2010 9:05 am ]
Post subject:  Re: cracked my back

Bob,
Ill have to try some of those next time, I have some. The guy at woodcraft recommended a No7 Olson skiptooth 11.5 tpi, it cut like butter.

Devin

Author:  devincox [ Wed Jul 14, 2010 9:09 am ]
Post subject:  Re: cracked my back

Joe,
Thanks for the help. The repair turned out perfect. I was pretty dissappointed to say the least, now Im back on track.
http://www.devincox.com/images/backafterfix.jpg
http://www.devincox.com/images/topandback.jpg

Thanks,
Devin

Author:  Wayne Clark [ Wed Jul 14, 2010 11:00 am ]
Post subject:  Re: cracked my back

Consider getting a coping saw for this part of the process. It might take you 10 minutes to rough cut a top or back, but its really unlikely you would cause damage like that.

Author:  Bob Shanklin [ Wed Jul 14, 2010 2:42 pm ]
Post subject:  Re: cracked my back

I have cracked backs and tops using a coping saw. When I got my 600 dollar Dewalt scroll saw at an estate auction for a hundred, I was quite happy, and had no more cracking problems.

Bob

Author:  sonorgeek [ Sun Aug 01, 2010 1:33 am ]
Post subject:  Re: cracked my back

Looks to me like an obvious few drops of CA or Slow set 2 part epoxy. depends on how much you measure the acoustics of your repair, you can hide it for sure, after the back braces go on i would say the back would NOT be any less stiff? this is just my rookie assumption.

Ricky.

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