Repairing Cracked Back Plates
Source: Crack & Brace Repair
Back Plate Crack Repair:
Cracks in the back plate are often repaired in the same manner as the top plate cracks. To see those articles refer to:
Hairline Crack Repair in the Top Plate
Open – Aligned Crack Repair in the Top Plate
Open – Miss-Aligned Crack Repair in the Top Plate
You will find that most of the cracks, with the exception of very small or minor cracks in the guitar back will be miss-aligned and will need cross-patches installed. The reason for this is that most guitar backs are arched in some manner. This then introduces additional stresses that the back is subjected to, which means the back will not only split, it will go out of alignment as well.
That is where our Crack Alignment Jig comes into play. This jig will allow you to align the crack and reinforce and glue it at the same time.
For these types of crack repairs, you should follow the same procedure outlined in the articles above.
Outlining the procedure you would:
Apply cross patches at 2″ o.c.. Make sure you place a patch at both the beginning and end of the crack to prevent further cracking.
Use the Cross Patch Jig to align the crack and glue the patches
Clean out the crack with a saw blade
Make the splint
Apply the splint and glue it in
Plane the splint down to the surface of the back
Clean up
Finish is required
Full Length Back Plate Cracks:
Because of the stress discussed above, it does not take long for a back crack to progress until the back splits from end to end (depending on the crack location of course).
Remove the Guitar Back Plate: With these types of cracks you really should remove the back from the guitar to repair the crack. To do this see our article on Guitar Back Plate Removal. Once the plate has been removed, do the following:
Clean The Cracked Area; Clean the crack sides with Lacquer Thinner and Alcohol so you can remove all of the old wax buildup and dirt from within the crack.
Prepare a Back Reinforcement Strip: Prepare a back strip in much the same manner as the back strip down the center joint of the guitar. For instruction on making and installing one of these refer to this article on the Back Reinforcement Strip.
Glue Up The Back Plate: Place the back in a Guitar Plate Gluing Jig and glue it up tightly with 2-part Epoxy glue that has been tinted to match the back wood. ( You can get stain kits of aniline dyes for this purpose). Make sure the crack is aligned before apply the entire jig pressure.
Glue the Back Reinforcement Strip Into Place: Remove the back and clean up the glue joint. Fit the new Joint Reinforcement Strip. Glue the strip onto the back with a Go Board Gluing Tool with 2-Part Epoxy Glue. Cleanup the glue with chisels and a bit of sandpaper on the inside of the back plate.
Final Steps: Before you glue the back on the instrument, check the quality of the glue joint, the strip placement and if you adequately cleaned the glue from the back. For this procedure, please refer to the Article on Gluing a Back Plate.
Note: For Great Plans on the Go Board Gluing Tool and the Guitar Plate Gluing Jig, go to our Plan Shop. This is where you will find alls kinds of useful stuff including Guitar Building Plans, Guitar Side Benders, Gluing Jigs and Assembly Molds and Jigs. We also will be posting the free plans at the Plan Shop, so check back there often for a wealth of information.
Tags: back plate crack repair, closed guitar crack repair, fixing cracks, guitar back crack repair, how to fix a guitar crack
