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What I did for the one I alluded to in the previous post was to make a router jig out of 3/4” fibercore with a constant curve that just cleared the defect.

I double stick taped it to the top and used a short top bearing flush cut bit to rout out the defect to a shallow depth. I used that jig to trace an outline on the spruce filler and sanded it to fit. Glue it in and re-rout the channel

One could even make a reciprocal convex jig to form the filler piece.

I think you could get a good repair if you can match the grain lines from an offcut. A burst would cover it nicely. Once bound I don’t think the area of exposed repair would be all that big. I would at least try that before retopping.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Yep, I've done that one. It was from not holding the work firmly enough during a climb cut. My advice is not to try and fix it. Make a new top first, then cut that one off. As a sprayer once told me - "Your first loss is always the best one." By that, he meant - take the loss, do it again. Once you start trying to fix it, the job will get longer and longer.

Take it on the chin and start again.

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nigel

http://www.theluthierblog.com

"It's then just a case of applying the the right pressure on the guide bearing. Too much and you indent the sides with the bearing (and overload/over heat all the bearings involved), too little and you can get what you got."

Actually, I have seen the sides scored by the bearing from too little pressure holding the bearing against the sides. The bearing is not supposed to spin but rather roll along the side as you make the cut. If your bearings are overheating you need to oil them with something like motor oil, and when they get "crunchy" replace them. The grease they come packed with only lasts so long.

"I use the LMII bit and sharpen it after every use by lapping it on a diamond plate."

If you sharpen your bit after every use you might want to switch to high speed steel. 2 reasons - it's easier to sharpen and it will take a sharper edge than carbide. Carbide is great for cutting abrasive manmade materials and retains a "dull" sharpness much longer than HSS, but never gets as sharp. You don't see carbide tipped chisels.

My sympathies Brad.
I had something similar, but much smaller, on a recent build at the neck shoulder area, using Trevor's climbing cut all the way.
I suspect that my (very thin top) wasn't properly glued to the sides/linings in that area, or maybe wasn't clamped quickly enough (last area to be go-barred)
If the guitar hadn't been an trial build and for me, it would have been re-topped. As it was, I just filled it with superglue and spruce dust after shellacing it.
But it still niggles me!

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Thanks for all the help.

I did a deep clean on the shop this morning to give myself some time to think. I decided to re-top it. The dude this is for is a special one so I don’t want to have that nagging me.

Question - I’ve never taken a top off. There was mention a couple times of routing the top off. What does that process look like? Left on my own I would have applied heat and tried to remove the top. I like the idea of routing it off because it doesn’t mess with the lining glue (I think )

Brad


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Yikes I have been there in the exact same place on my guitars using the same direction climb cut; actually a few of times. Once I re-topped most times I was able to fit it in the purfling scheme. Each time it happened to me was do to inattention letting the router run away or the guitar in the carrier run away. I have a system where I guide the router so I need to make sure both the router and and guitar in the carrier are secure. I now clamp the carrier to my bench and hold the router with two hands especially as I climb cut into the endgrain.

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http://www.Harvestmoonguitars.com

Ouch!

If you searched the archives like you said than you may have found a tread I started a few months ago on the same topic. Just like all the experienced luthiers said in that thread, there is no hope of fixing it with a splint. Even though I had a perfect match and inlayed it really well with a finish on it sticks out like a soar thumb.

I agree with Trevor when he says retopping actually will go faster, smoother and better then any other option. Unless you want wide purfs or a sunburst.

I was making an 000 so what I did was take the top off that guitar and build an 00 with it. So you can still use it for something if you are clever.

Brad there are many ways to take the top off, since I use fish glue . I just use a bit of heat from a hair dryer and wiggle my way around the circumfrence of the top with a dull spatula . a little bit of DA on the spatula helps to break down the glue. If I was using a laminate router I/d go about 1/16 in past the binding /purfling, and cut it out in small increments of 1/16in in depth of cut . Many ways to do it !!!

"If I was using a laminate router I/d go about 1/16 in past the binding /purfling, and cut it out in small increments of 1/16in in depth of cut . Many ways to do it !!!"

If you do it that way (depending on your setup) you might want to leave a couple of "tabs" around the perimeter to support the top until you have routed most of it off - you don't want the router dropping into the side when the top falls.

as clay said, or a prop wedge/block between the braces and top, so it does not fall in after routing through the top and bracing which will be thicker than the top ???

What about just using a smaller bearing on the binding jig? Like you said, leave a few spots so it doesn’t collapse?


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Heat gun and spatula...

The only thing that worries me is that I use solid linings that are glued together with fish glue. I’m a little worried about the linings delaminating. What do you think?

Oh, btw.. you asked about the top thickness, it’s .104

Brad


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Brad, you can salvage the rosette with a variation of this method I used to replace one in a closed box.
Getting a good fit on the center is key.

viewtopic.php?f=10101&t=49664

Routing off the top should be fairly easy, multiple passes inboard of the linings until only the blocks and let in braces remain. Saw off the braces, chisel away material at the blocks, return to the radius dish for a touch up. I guess this means losing all the top bracing.

Although this is a real heartbreaker when it happens, the new skills learned with a good save kinda makes up for it.

B

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My memory is so good, sometimes I remember things that never happened.

Makes sense. Thanks, Bri.

I tried the idea of slowly stepping in using smaller and smaller bearings on the binding jig. That got me close but not all the way.

I’ll have to use the palm router as you described.



Here you can see he side strut. Based on how the lining is laminated I have about another 0.070 to go.



Also, just a side note for anyone using this jig, I put felt dots on the base so it doesn’t damage the top if you pull out past the donut (insert Michael Scott joke here).



Brad


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Sadly from time to time I have to rout a top off too.

I usually go all the way around with the router past the linings but not all the way through, then cut the last .010 with an exacto. The only need for heat is at the tail and head block. If you're careful and lucky, you can remove it without opening the seam at the tail. If you manage that, depending on your brace layout, you may be able to salvage the top for a smaller instrument...

When you make a new top try to do a better job gluing the center seam. If not glued properly the glue joint will surely come loose under string tension.

Here is how I remove a top that will be trashed: Put on the the bearing that will get the widest cut and set it to the depth of the top and rout the top all the way around, then use a jig saw to cut the top off to about 1/2" from the lining and end blocks, remove what remains of the top with a hand plane, sand the edge some to get a fresh surface for installing a new top. This takes me less time than using heat and spatula and there is much less chance of messing up the lining.

I’m curious why you say this? Are you mistaking the pencil mark down the center of the top for a poor center seam?



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Ok, after a little heat and spatula time we are off. Now to get that rosette!







Brad


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It looks like you did a good job removing the top. I would save the top and make a new rosette. It looks like a fairly simple rosette and will be more trouble to remove it than to make a new one.

Gaah! Too late.



I planed the braces down pretty far then ran it through the drum sander.


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The rosette is free!

I always keep the soundhole cutout. I use it to make a little something for the recipient. Plugging the cutout and two strips of purfling into the soundhole worked perfectly.





Winner winner, poulet dinner.



I’m done for today. It’s raining all weekend so I’m taking my son to Dave and Busters.

Thanks again for all the help and suggestions. Could have been worse I guess.

Brad



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Thanks for starting this thread. I have routed binding channels on 80 guitars and always felt totally safe using a climb cut. Good to know that it is not totally safe and that complacency is unwarranted.

Nice job on the top.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

I know it’s a little late, but oftentimes mistakes are just an inlay opportunity.

For future reference, once I switched to a downcut spiral and custom (read: I made it) bearing foot with a zero bar, tearout has been a non-issue. I think I have a vid of my headstock routing setup somewhere, which I redid my body binding jig the same way; both DW611 based, which I think you’ll like.

And, it used to be beer, Hefeweizen preferably, but my brother turned me on to Whiskey the other year, so Bourbon it is.

Use a thick blk/whi/blk with a wide zip strip of abalone and see if it cover the damage