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Please Advise On Best Way To Finish Crack Repair


djhollowman
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Hi all,

I'm currently repairing a Crafter electro-acoustic which had a broken headstock.

I've cleaned and glued the head back on, and it's worked amazingly well. I have a very strong join now!

The front will be re-veneered, so there's no finishing issues there, as it will all be re-done.

However, what's the best way to complete the repair on the back and sides of the head?

I've achieved quite a good join:

PB180004.jpg

PB180001.jpg

I don't mind having to refinish the entire neck. It's what to use to fill the cracks I'm struggling with.

The neck is mahogany, should I fill the cracks with mahogany dust and glue?

I have looked around the forums, but I find the search function almost useless TBH. I just can't seem to get it to work how I want!

Any help appreciated,

DJ

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I'm a little concerned - if you have cracks which require filling, you can't have a tight enough joint for the glue to do much good. What kind of glue did you use?

With a crack like that, and a good tight repair, you should have very little visible glue or crack left, just surface checks in the finish.

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Yeah, surface checks are what I'm talking about. Nothing serious, but obviously I don't have the broken splinters to reset, which would have helped. It's particularly the little areas like that which I will need to fill. Perhaps the flash from the camera makes the joints look worse than they actually are! I want the joined areas to feel smooth under your hand.

I used white Evo Stick wood glue, and I realise now that I should've cleaned it off better before it dried, oops!

I'm pretty sure the joint is tight - I can lift the entire guitar by the broken end from lying flat, keeping it still flat. Also, the frontal re-veneer will add strength.

DJ

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Anyone notice that it has looks as if it either has been repaired before or it is a laminated neck in layers? could be the grain plying tricks on my old eyes:) I would redo the joint just before the breakover of the headstock and replace it if it were me.

MK

Edited by MiKro
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Anyone notice that it has looks as if it either has been repaired before or it is a laminated neck in layers? could be the grain plying tricks on my old eyes:) I would redo the joint just before the breakover of the headstock and replace it if it were me.

MK

You're right, it's a laminated heastock. There's a scarf joint right up through most of the headstock. If you look at the 2nd photo you can see where the original scarf joint was on the left side of the picture. The break has happened near to that join on the left side.

I did wonder about cutting the broken neck end flat, and re-scarfing an entirely new head on. This might still be an option, if what I've done doesn't work sufficiently, but I thought I'll try re-attaching the old one first!

DJ

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Give the whole area a very gentle levelling, nothing coarser than 400 grit. You might also try using a hard pencil erasor to clean the glue away around the joint. It may be due to the photo, but it looks like you have either a good deal of squeezout to remove, or quite a thick, very white, glueline.

Show some photo once it's been lightly levelled and cleaned of any squeezeout, and I'll be able to offer more advice.

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  • 3 weeks later...

Right. Do you have any dyes available?

You need to get the areas where finish is missing to match the colour of the lacquered areas. The quickest way is to wipe it over with a cotton bud dipped in stain/dye then wipe of any excess with a cloth, so it only remains in the bare areas. Once you've got a decent colour match, spot fill the cracks with CA or lacquer, depending on the finish used - as a rule of thumb, cheapo imports will be a job for CA.

Once your drop fills have cured fully (24 hrs for CA 2-3 weeks for nitro) level with a razor blade scraper then 600 grit, then check for shiny areas. If there are none, you've got no low spots, so wet sand to 1500 or so, and buff out. If you've got shiny spots, repeat your filling/levelling until they're gone, then level and buff.

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Aha! OK, thanks! Makes sense.

I have no dyes or stains. What kind would I need? Does it matter if it's oil or water based?

(BTW, don't know if this is significant here or not, but - when I was sanding the existing finish, the dust was coming off in a distinctly yellow colour. To my mind this would suggest a coloured finish was originally used, as opposed to a clear finish over coloured wood.)

I'm comfortable with the CA/laquer drop fills part. Done that before.

Finally, what buffing compound(s) would you recommend? There's a bewildering array of them available!!

Thanks again,

DJ

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Oh yeah, PSW: I reckon inlaying the back would be a serious amount of extra work! :D

I have veneered the front, and it's come up really well. I deliberately went for quite a thick veneer, thinking it will add strength to the repair. It's thicker than I would have liked, to be honest, but I suppose I can always sand it thinner!! I've already had to shape it at the area where the nut sits.

This was how it looked when I got it:

PB160015.jpg

PB150003.jpg

The original veneer on the front was really thin, <1mm. My new one is about 2.5mm. I had to take some of the front off before glueing the new one on. I think I will sand the new one a bit thinner though!

DJ

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  • 2 weeks later...

Here's a quick update:

PICT1643.jpg

It's getting much better now. I still don't have the colour match as accurate as I would like yet. I'm applying wood dye, but it needs to be more yellow.

There's still a visible line where the break was, but as I didn't have the broken chips to glue back in, I had to fill the slight crack with CA and sand flat. It's lovely and smooth, just wish I could make the line less visible!! (The straight line across the back of the headstock was always there - that's where the original headstock-to-neck joint is)

DJ

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Chances are the original finish was amber coloured - the pale lines where you lost lacquer strongly suggest this, as does the pee-coloured slurry when wet sanding :D

However, you can't easily colour CA prior to drop filling, so that's why you need to stain/dye the light lines first. What you've got now looks pretty good, and you're unlikely to get an invisible repair on a poly finished instrument anyway. I'd call it done.

To buff out I use Meguiars scratch-X. You will need to sand to at least 1500 before buffing as the scratch X isn't abrasive enough to remove anything coarser than that without taking forever...

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Chances are the original finish was amber coloured - the pale lines where you lost lacquer strongly suggest this, as does the pee-coloured slurry when wet sanding :D

However, you can't easily colour CA prior to drop filling, so that's why you need to stain/dye the light lines first. What you've got now looks pretty good, and you're unlikely to get an invisible repair on a poly finished instrument anyway. I'd call it done.

To buff out I use Meguiars scratch-X. You will need to sand to at least 1500 before buffing as the scratch X isn't abrasive enough to remove anything coarser than that without taking forever...

Thanks for your help! I'm pretty pleased to read that you think it looks pretty good - this is my first repair like this. I've learned a lot already with this one.

I made absolutely certain that it is structurally sound, because that's obviously the key thing - doesn't matter how pretty it is if the repair isn't strong enough.

I'll check out that Meguiars as well.

It's nearly done actually. Still have to thin down the front veneer a bit, then it's onto finishing the front. I have replacements made for the (cheesy) original stickers already.

Thanks again,

DJ

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  • 1 month later...

Bump!!

Well, basically finished this bad boy now:

P2130121.jpg

P2130125.jpg

Flash photography makes it look worse than it is!

Having got the repaired area stained to a nice colour match, you can imagine my disappointment when the act of applying the finish actually removed the stain and made the colour-match look terrible!! :D

So, I sanded off all the coloured stain from the neck and refinished with Tru-Oil; nice and smooth but not sticky. And the colour is exactly the same all over the neck! (...and it's a nicer colour now!)

I'm really quite pleased with this repair now, especially since it's my first attempt at a headstock re-join. I've had it strung up and been playing it as well. I left it overnight, strung up to tension, and it was still perfectly in tune the next day, so I'm happy that the join is structurally sound. (Actually I could lift up the entire guitar by the repaired headstock end - I did try it!!)

So, now either the former owner can pay for the repair, or if she doesn't want it back I'll have an inexpensive keeper.....I can't lose with this one! :D

DJ

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  • 1 month later...

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