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  #1  
Old 09-27-2020, 03:14 AM
Nahil.R Nahil.R is offline
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Default Binding Channels

Quick question ...

I understand that many luthiers use a light coat of shellac to seal the edges prior to routing the binding / purfling channels.

I wanted to know if I could use a light coat of wipe on poly (minwax) to the same affect? or would it create adhesion problems when gluing in the edge trim?

Thanks.

Nahil.
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Old 09-27-2020, 08:25 AM
D. Churchland D. Churchland is offline
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Are you trying to minimize the risk of tear out when routing?
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Old 09-27-2020, 10:37 AM
Shuksan Shuksan is offline
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I've never sealed the surfaces before routing the binding/purfling channels and I've had zero problems.
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Old 09-27-2020, 06:07 PM
RonMay RonMay is offline
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I've watched videos of Jerry Rosa on Ytube many times rout the relief for the binding and he never coats it with anything.
Just don't rush it.

Ron
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Old 09-27-2020, 06:55 PM
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Bruce Sexauer Bruce Sexauer is offline
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If there is any doubt whatsoever about how sharp your router but is, put in a new one. Go slowly, and inch or two a second, and climb cut the whole way. Do not let the router get away on you, and do NOT cut in the other direction, even as a clean out. I have never sealed before cutting.
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Old 09-28-2020, 02:36 AM
Nahil.R Nahil.R is offline
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Thanks guys, I think it was a Robbie O'Brien video I was watching where he applied a light shellac washcoat.

I guess I will just work slowly with sharp bits

The back was attached yesterday!!

I'll hopefully post some photos soon.

Cheers,

Nahil.
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Old 09-28-2020, 07:11 AM
redir redir is offline
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Shellac is often times used because it will also be used as a base coat on the instrument. If you were going to finish the instrument with the Polyurethane then I's say sure go for it. If not then no.

I have used it before routing bindings. I think the idea is that it acts as a sort of glue. I'm not sure it makes much of a difference. I do still do it though not so much for the purpose of holding wood fibers together but once the binding is cut then when I use tape or rope to clamp the bindings on it's good to have shellac around the perimeter so that tape does not pull up wood fibers and any glue squeeze out doesn't stain the wood and is easier to clean up.
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Old 09-28-2020, 08:09 AM
charles Tauber charles Tauber is offline
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Quote:
Originally Posted by redir View Post
... once the binding is cut then when I use tape ...to clamp the bindings on it's good to have shellac around the perimeter so that tape does not pull up wood fibers...
That is the reason that I started applying a light coat of shellac prior to cutting binding rabbets. It wasn't a problem with "normal" masking tape, but when I switched to stronger 3M binding tape, the first time I did it, removing the tape took significant wood fibres with it. Shellac prevents that. During all the time I used regular masking tape, rope and elastics, I didn't apply shellac.

That said, wipe-on poly would serve the same purpose. It doesn't need to be a thick coat to prevent tape from pulling-up wood fibres. Shellac dries almost instantly, though, whereas poly will take at least an hour or more.
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Old 09-28-2020, 08:32 AM
D. Churchland D. Churchland is offline
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Quote:
Originally Posted by charles Tauber View Post
It wasn't a problem with "normal" masking tape, but when I switched to stronger 3M binding tape, the first time I did it, removing the tape took significant wood fibres with it
If you pull it straight off that's exactly what will happen. Pulling it at an angle to the side will prevent that. Or just use something like frog tape.

To answer the OP's question. It just adds alot of time to your build to do it that way. Low tack masking tape on the more tear out prone areas is faster and does the exact same thing with less work.
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Old 09-28-2020, 08:45 AM
charles Tauber charles Tauber is offline
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Quote:
Originally Posted by Will Kirk View Post
Pulling it at an angle to the side will prevent that.
Tried that. It doesn't prevent it.

Quote:
Or just use something like frog tape.
The reason for using the specific 3M tape is that it has a much higher breaking strength than typical masking tapes.

Quote:
Low tack masking tape on the more tear out prone areas is faster and does the exact same thing with less work.
That lower strength masking tapes eliminate the need for coating the top might be a good reason to forgo the higher strength tape. The higher strength tape eliminates tape breakage, but might not be worth the trade-off. Applying a light coat of shellac takes 5 minutes. 5 minutes versus no tape breakage and being able to apply a lot more force on the tape. No clear "right" answer, just personal preference, perhaps.
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Old 09-28-2020, 09:44 AM
redir redir is offline
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Knowing the runout direction helps when removing tape but it's been my experience that is not foolproof either. Shellac on the other hand is. I like it as a preventative measure.
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Old 09-28-2020, 10:12 AM
Nahil.R Nahil.R is offline
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Thanks for the responses guys. It makes sense to use a preventative measure to protect the guitar, especially if it takes such a short time.

I am building with an Engelmann top so I may apply a light coat of poly to the area to be routed. I will also be finishing the guitar with it so nothing to lose and potential tearout risk reduced!
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Old 09-28-2020, 10:54 AM
Shuksan Shuksan is offline
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Quote:
Originally Posted by charles Tauber View Post
That is the reason that I started applying a light coat of shellac prior to cutting binding rabbets. It wasn't a problem with "normal" masking tape, but when I switched to stronger 3M binding tape, the first time I did it, removing the tape took significant wood fibres with it. Shellac prevents that. During all the time I used regular masking tape, rope and elastics, I didn't apply shellac.

That said, wipe-on poly would serve the same purpose. It doesn't need to be a thick coat to prevent tape from pulling-up wood fibres. Shellac dries almost instantly, though, whereas poly will take at least an hour or more.
I avoid tear out when removing the tape by heating the tape with a blow drier as I go along pulling the tape off. Works great.
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Old 09-28-2020, 12:15 PM
charles Tauber charles Tauber is offline
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Quote:
Originally Posted by Shuksan View Post
I avoid tear out when removing the tape by heating the tape with a blow drier as I go along pulling the tape off. Works great.
Sounds like a good solution. Thanks for sharing it.
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  #15  
Old 09-28-2020, 12:48 PM
Shuksan Shuksan is offline
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Quote:
Originally Posted by charles Tauber View Post
Sounds like a good solution. Thanks for sharing it.
Just be careful not to fry your fingers. The air coming out of a garden variety blow drier can be surprisingly hot.
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