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Post by gawpertron on Apr 27, 2021 19:50:53 GMT
First time builder here. I have a question about how you would go about repairing accidental knife cut or mark damage?
I've just finished hand cutting the binding groves on body top of an acoustic guitar, but in doing so my hand slipped a few times and has left a couple of knife marks. The marks seem a bit thin for filling with a saw dust paste so I'm not sure what to do reduce visible marks?
In hindsight I think just using the chisel would have been better rather than trying to compensate afterwards with a marking knife for the shallow cuts made by a DIY gramil... but hey, it is what it is and I've had to learn the hard way.
Cheers for any advice.
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colins
Luthier / Guitar Maker
Posts: 2,395 
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Post by colins on Apr 27, 2021 21:11:54 GMT
Photos would be helpful. They can't be posted direct, upload them to a hosting sight and then provide the links here.
Oh and welcome to the forum.
Colin
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ocarolan
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Post by ocarolan on Apr 27, 2021 21:26:43 GMT
Hi gawpertron and welcome to the Forum. Lots of experienced instrument makers here, (though not me!)- I'm sure others will be able to chip in esp if , as Colin suggests, you show some photos. In the meantime, have a good look around and feel free to join in wherever you like. Keith |
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Post by gawpertron on Apr 28, 2021 13:26:09 GMT
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garynava
Luthier / Guitar Maker
Posts: 460
My main instrument is: Stanley No.5
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Post by garynava on Apr 28, 2021 15:09:38 GMT
Difficult to repair or disguise cuts going across the grain. I think that's one to chalk up to experience.
Good luck with the rest of the build.
Cheers Gary
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davewhite
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Post by davewhite on Apr 28, 2021 17:32:42 GMT
How deep are the cuts? If not too deep and as it looks as though you haven't put the binding on yet I would be tempted to carefully sand down the the top perimeter around the area from end of bass lower bout to end of treble lower bout to see if the mark comes out with enough top left there. Don't concentrate your sanding on the scratch area so you keep and even top shape rather than a dip where the cut is. It's a sort of feathering process of the top perimeter. Assuming you have learned the knack now of cutting the binding channels you can recut the channel where you have thinned the top to keep the binding channel a constant depth. Many makers thin the top around the lower bout perimeter as part of their normal process. Good luck with the rest of the build - there will be many more "fixes" ahead  |
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colins
Luthier / Guitar Maker
Posts: 2,395
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Post by colins on Apr 28, 2021 18:32:05 GMT
Yes I agree with Dave, (we usually do). The cut mark doesn't appear to spread too far into the top from the edge and most of it will be over the lining, so structurally you good. I do always slightly thin the perimeter of the lower bout, use 320 grit on a cork sanding block and gently sand in the direction of the grain for a 5cm or so all round the lower bout area below the bridge level. Don't try and get it all out before putting the binding on as it's easy to round over the edge and you'll be sanding the whole top again anyway.
Part of the learning process of building guitars is how to correct, or disguise, your cock-ups.
Kudos to you anyway for cutting the channel with a gramil and chisel, if you need to deepen the channel then carry on with a chisel or use a file, marking knives are not easy to control unless against a steel edge.
I do have a spare Schneider Gramil that I don't use now sitting on a shelf if you intend to do this again.
Colin
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Post by lindsayguitar on May 3, 2021 17:08:01 GMT
Hi there
These things happen, and I well know that sinking feeling when perfection moves a little further away, but you got this far and another footprint in the sands of time is not the end of the world.
My instinct is not to extend the effect of this mistake but to locally thin the top after you have attached the binding and avoid a polished finish!
Lindsay
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Post by gawpertron on May 4, 2021 7:40:39 GMT
Thanks for your suggestions. Sanding out the areas seems to improve the blemish some what and yes this is another mistake of many I have already made and I'm sure there are more to come, it was just one I couldn't think of a way to hid it. I might try sanding it out further near to the time I apply a finish.
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Jo whoever he is.
