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 Post subject: cracked my back
PostPosted: Tue Jul 13, 2010 8:31 am 
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Mahogany
Mahogany

Joined: Thu Jul 23, 2009 4:54 pm
Posts: 96
First name: Devin
Last Name: Cox
City: Edmond
State: Oklahoma
Country: usa
Focus: Build
Status: Amateur
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


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 Post subject: Re: cracked my back
PostPosted: Tue Jul 13, 2010 12:47 pm 
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Koa
Koa
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Joined: Tue Aug 19, 2008 12:17 pm
Posts: 534
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


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 Post subject: Re: cracked my back
PostPosted: Tue Jul 13, 2010 3:37 pm 
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Mahogany
Mahogany

Joined: Thu Jul 23, 2009 4:54 pm
Posts: 96
First name: Devin
Last Name: Cox
City: Edmond
State: Oklahoma
Country: usa
Focus: Build
Status: Amateur
Thanks Joe. Excellent news. I will pick up some thin CA tonight and give it a try.

Devin


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 Post subject: Re: cracked my back
PostPosted: Tue Jul 13, 2010 10:22 pm 
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Contributing Member
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Joined: Tue Mar 04, 2008 11:55 am
Posts: 539
First name: Bob
Last Name: Shanklin
City: Windsor
State: ON
Country: Canada
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


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 Post subject: Re: cracked my back
PostPosted: Wed Jul 14, 2010 9:05 am 
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Mahogany
Mahogany

Joined: Thu Jul 23, 2009 4:54 pm
Posts: 96
First name: Devin
Last Name: Cox
City: Edmond
State: Oklahoma
Country: usa
Focus: Build
Status: Amateur
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


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 Post subject: Re: cracked my back
PostPosted: Wed Jul 14, 2010 9:09 am 
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Mahogany
Mahogany

Joined: Thu Jul 23, 2009 4:54 pm
Posts: 96
First name: Devin
Last Name: Cox
City: Edmond
State: Oklahoma
Country: usa
Focus: Build
Status: Amateur
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


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 Post subject: Re: cracked my back
PostPosted: Wed Jul 14, 2010 11:00 am 
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Cocobolo
Cocobolo

Joined: Thu Jun 23, 2005 9:36 am
Posts: 381
Location: United States
First name: Wayne
Last Name: Clark
City: Driftwood
State: TX
Focus: Build
Status: Amateur
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.

_________________
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http://driftwoodguitars.blogspot.com/


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 Post subject: Re: cracked my back
PostPosted: Wed Jul 14, 2010 2:42 pm 
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Contributing Member
Contributing Member

Joined: Tue Mar 04, 2008 11:55 am
Posts: 539
First name: Bob
Last Name: Shanklin
City: Windsor
State: ON
Country: Canada
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


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 Post subject: Re: cracked my back
PostPosted: Sun Aug 01, 2010 1:33 am 
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Walnut
Walnut

Joined: Sat Aug 29, 2009 1:38 pm
Posts: 16
First name: ricky
Last Name: collins
City: mount carmel
State: illinois
Zip/Postal Code: 62863
Country: us
Focus: Build
Status: Amateur
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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