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Bit late for that, no?

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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.

Hey Brad, I haven't heard it mentioned, but a "down shear" bit will have an upward force when cutting. Especially if it suddenly takes a deeper cut. I'm not familiar with the LMI tower rig. If the router is light, counterbalanced, and can rise easily, it could conceivably climb up far enough for the bearing to drop into the cut rabbet and get exciting. This might be especially true if the binding was tall (yours looks pretty tall) and the cutter doesn't clear the top when the bearing drops into the rabbet.

Just a theory.


cheers.

I was wondering about this too. The tower I have isn't counterweighted at all so the full weight of the router and the carriage keeps it firmly planted on the body.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Interesting. It does take very little to lift it because of the new design of the jig.

I was using the SM bit with the bearing extension. It’s a downshear bit.

https://www.stewmac.com/Luthier_Tools/T ... r_Bit.html

I put a test body I keep around (a failed build ) in the carrier and was replaying and thinking about what might have happened. I noticed that when I was mimicking the climb cut where the issue occurred, I was pulling the carrier toward my body with both hands. Rather than pushing against and steadying with one hand and pulling with the other. In other words, there was not as much pressure pushing against and keeping the thing from running away. Also, I don’t know if it is my table or just the nature of the carrier but it is slick as snot. I can completely see how it took off running on the climb cut. I may need to reposition the tower so I’m more facing it directly rather than it being to my left side.

I’m almost ready to close the box again, so we will find out soon!!

I also plan to take a few more passes this time. Once I have the depth set I’ll use a 3 bearing step down to the final depth. Last time I did it in two bearing changes, but still.... it really shouldn’t have happened.

Brad




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You know if there is not much downward force on the router riding up and skipping is a real possibility.

I am still using the original LMI Ribbecke style jig from 2002 for the most part and with that the full weight of the router bears on the guitar. I actually thought that was a little much and rigged a pulley system to take a little weight off but there is still a good downward force holding the finger against the top.

It would be interesting to see if any other users of the new LMI jig have had similar problems.

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I had that happen recently. My router bit was chipped


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Hey I just saw a product called purflex. It come in 1/4 width. Might be enough to cover the damage


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https://youtu.be/j_8lfDP2dCk


Purflex


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To quote Colin above, Bit late for that, no?

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

I’m finally back to putting the new top on this one. I have radiused the top rim again and flattened the upper bout a la Hesh’s tut.

Question though - the binding channel is still halfway there after radiusing the rim. Should I try to flush trim the top to the side or to the binding channel? If I trim to the side there will be a small overhang that the rabbet bit will be trying to trim. It seems safer to flush to the binding channel, or at least as much as possible?

I’m new to the world of re-topping.





Brad





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Seems safer to have the top flushed to the remnant of the binding channel to avoid tear out of the top when routing the new binding channel. How would you go about doing that though?

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Brad, so sorry u had to go through this. There but for the grace of God go we all. Glad you chose the harder path to fix. Do you apply hand pressure to that binding slot cutter? It would seem u cannot. I'd find something like that hard to trust. I use the LMI bearings and cutter. Always clean the bit with mineral spirits before using. Makes a big difference as oils crystallize on the bit. I have tossed all but one Bosch Colt router. Its 2011. With good the good bearings. DW 611 on everything else. Used to be u could read about the Colt issue on precisebits.com. They don't even mention that router anymore.

Yeah, I had the same issue, I can’t think how I’d do it with just a laminate trimmer. I think it will just wind up being a bunch of handwork, which is ok I guess. Lord, I’m so lazy.


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Thanks, Mike.

I spent a lot of time post-mortem thinking about what went wrong. I had the binding jig base mounted in a way where I wasn’t facing it directly. Meaning, it was to my left and I was putting pressure to my left to keep the body pressed against the bearing. I believe I let up because of the awkward positioning and the router rode up the side because of a lack of pressure.

I re-mounted the base since then so that I’m facing it (pushing the work “into” the bearing) and haven’t had an issue with the last few. I think I’m in a good spot now (knock wood).


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Maybe you could remove the overhang in two steps. Use a flush trim bit with the bearing riding on the side to take the top overhang back to flush with the sides (light passes, hand held) and then follow up with your binding channel routing rig with the LMI cutter and the appropriate size bearing to route the rest or almost all of the remaining overhang off. Then rout your new channels.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

I'd graft a piece os sycamore in that area and a little larger then go in with a wood burner and write some kind of inscription to my friend. He will think you did it on purpose and if something meaningful about your friendship will make the build that much more special.

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Michael F Smith
Goat Rock Ukulele
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I think I'd fill the binding channel before gluing the top on. Use any scrap wood you have, thin it to your binding size, bend and install. Use thin CA very sparingly so you have little to no clean up of the sides to do, then trim it flush with the rim top. Now you have full width to glue the top to. Then trim your top and re-cut your binding/purfling channels.

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Thanks, Rod. I think that's the winner right there. I have some scraps of walnut binding already bent to dred shape. Appreciate the idea!!

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I don't really see how it matters any way. If there was no binding channel you would still be using a router to flush cut the over hang it right?

I'm probably doing a poor job explaining...

The binding channel is already cut (although it's not full height now because of putting the radius back on the rims). Once I glue the new top on - if I flush trim the top to the sides there will still be a 0.070 overhang where the top material is overhanging the void of the binding channel. What I was concerned about was if I put the body through the binding jig to flush that last bit there might be tear out or another disaster because that thin overhang vibrating while going through the cutter.

Rod's idea gives some confidence that the new top will survive the binding jig. I think.

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I have had it happen exactly like that twice. On a climb cut when you hit the endgrain you need to make sure both the top guitar and the router is securely held otherwise it will run on you. When it runs like that across the endgrain you get that exact result. One time it was not so bad and I cut for purfling, the other time I replaced the top. I still do that climb cut at times but really hold the router, In your case the cradle and body. Now for the lower bout I start on the other side and do a conventional cut across the bottom end grain and then to the climb cut on the treble side down to where I stopped.

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this is not the router or the bit or the jig. You were feeding in the wrong direction. When doing this you have to think of the angle of attack of the cutter bit. In this , it is a typical result. Lesson learned.

Think of how the cutter is working with the wood. Once you get to the point the the angle of cutter attack is into the work this will result. Had you route cut that area the angle of attack would have the cutter coming out of the work not into it.

Up cut or down cut wouldn't make a difference .

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John Hall
blues creek guitars
Authorized CF Martin Repair
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You Don't know what you don't know until you know it

I think you're overthinking the overhang. I don't ever actually flush cut. My intitial rout is .060 by a hair under a quarter. The overhang you have now is no different than the overhang you originally had, it's just inset that .070. If you follow the proper climb cut protocol (stewmac has directions) you should be a ok as is...

John, I want to make sure I’m getting what you’re saying...

Up cut / down cut in this context - are you referring to climb cut (direction) or router bit style (up / down cut bit)?

Brad


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I Know I am the wrong John but read this if you have not http://www.leevalley.com/us/shopping/TechInfo.aspx?p=56809. You can see what John is talking about. Figure 5 is what happened to you. As you come around the lower bout and hit the end grain the router pushed the carriage away or the tower slightly and the router bit bounced along the lower bout. The damage is not the router cutting so much as smashing into your wood. That is way there is so much compression in the damage.

The following excerpt is what I was trying to say. I did this twice before I finally learned how the stewmac pattern while avoiding tear out at the wide part of the bouts can lead to what you have. With the tower one might not have good control of both the router and the carriage to reliably do that climb cut. It does not take much movement to have what is in Figure 5 to happen.

In a climb cut, the bit is cutting on entry and has the effect of pushing the router away from the workpiece. If not resisted by the operator, the bit can exit fully from the cut and "climb" its way along the workpiece,

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