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Binding & Purfling Question...
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Author:  RichB [ Wed Apr 19, 2006 8:47 am ]
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OK...I'm getting the nerve up here to rout for the binding after stalling around for a few weeks (first time). I have a binding jig that I got from John Hall and it's hooked up to a PC 7310 laminate router. I'm using the BB router bit set from Stew-Mac.

What I'm not sure of is:
1. In what direction do you rotate the guitar body while the routers cutting? I'm trying to recall what everyone here has said, and clockwise comes to mind?

2. And...Which do you cut first the top purfling, then the binding, or vice-versa, or does it matter?

The binding is flame maple and the top purfling is going to be a 5-ply blk/wht/...plastic.
Setup:
Author:  RussellR [ Wed Apr 19, 2006 9:35 am ]
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Anti Clockwise is a normal cut, but it helps to climb cut certain areas to avoid tearout, if you go to stewmacs site and bring up the instruction for their kit it has a great diagram that illustrates the climb cut positions.

with a bearing cutter I'd cut the puflings first as the bearing needs the binding area intact to index off.
Author:  RussellR [ Wed Apr 19, 2006 10:09 am ]
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Hi Rich

This is the diagram I was talking about.




Todd

Thats a great idea to fit a double bearing , I cut my bindings first, but I use a trimmer with a guide bearing so can adjust the height of the bearing.
Author:  Alain Desforges [ Wed Apr 19, 2006 10:28 am ]
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Richard, don't do like I did... I had decided to cut the binding first and then the purfling (like Cumpiano/Nathelson recommend in their book)... BIG MISTAKE... the bearing winded up climbing in the binding channel and next thing I knew, I needed another bearing (smaller) and some extra purfling material to fill in my new deeper than wanted purfling channel.... I was lucky I saw it in time... It could of been even worse... You absolutely need the complete side (sans binding channel excavated) to have the bearing register... If you have a Gramil, you can always go around and just lightly score the channel to avoid tear-out and I think this little added care will provide a better result. Hope this helps...
Author:  Rod True [ Wed Apr 19, 2006 2:00 pm ]
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One thing I would recommend is to do the purfling line first, but do it in two stages. Those straight flute bits sure like to grab the end grain in these areas



So if you do it in two stages (depth of cut into the sound board) you will help eliminate the potential for ripping of a chuck of the top, just when you get this far. It can happen. Also running in the first direction with the added arrows will help, but there's no guarantee that it won't still blow out the top.Rod True38826.9603472222
Author:  Rod True [ Wed Apr 19, 2006 2:04 pm ]
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Rich, Also, it may be a good idea to run the back first. That way you get practice and if anything does happen, it's much easier to hide in the rosewood versus the spruce.
Author:  tippie53 [ Wed Apr 19, 2006 2:49 pm ]
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I just did 2 guitars today. I love the Stew Mac bearing set. I do my cutting high to low to avoid tear out. If you take your time and go nice and slow all will work out.
john
Author:  Brock Poling [ Thu Apr 20, 2006 2:14 am ]
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John is right. Roll down hill into the low spots.

Another tip.

Get rid of that carpet on your table. The biggest "problem" I have experienced with this set up is getting the guitar to move smoothly under the cutter. The carpet will only make it harder to move the carriage in a smooth even way.

Don't sweat this. Routing for bindings isn't near as hard as it looks.
Author:  CarltonM [ Thu Apr 20, 2006 7:26 am ]
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Whenever you have compound curves, as in a guitar body, to avoid chip-out it's best to route from side-grain DOWN to end-grain. So, as the above diagram shows, you'll start at the widest part of the upper and lower bouts, where the side-grain is, and move down into what becomes end-grain. Now, the narrowest part of the waist is also side-grain, but if you start there, you'll be moving UP into end-grain, and that means chip-out! Remember, always side-grain DOWN to end-grain.

BTW, the first diagram illustration (the climb-cuts) is suggested as your first cuts, followed by a continuous counter-clockwise route around the whole body.

WARNING!!! This is very important! Climb-cuts are potentially dangerous. The router LOVES climb-cuts; it wants to marry climb-cuts and bear its children. Climb-cuts offer the least resistance to the router, and it can then easily get out of your control and ruin your work or your body parts! Use your mightiest concentration, always, when climb-cutting!!!
Author:  Andy Zimmerman [ Thu Apr 20, 2006 9:19 am ]
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If you are using the SM bearing set, you MUST cut the purfling first!!! Add
the thickness of both together. If you do the binding first, you will have the
bearing fall into the binding groove instead of riding the sides of the guitar
Author:  RichB [ Thu Apr 20, 2006 11:57 am ]
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Thanks for all the suggestions & guidance here folks...

I took a stab at it today. The good news is no 'tear-out'. Per your diagrams, I followed them. Starting w/ the purfling, I went around a couple of times and everything went smooth. Definitely had some paranoia about the top flying out there, but I kept my kool and forged foward.

Brock...
I didn't have any problems w/ the carpet hanging up the manuevering of the body. It glides along nicely. I like that the rug provides a little resistance and lets me have some control over the whole rig. I had put on the shortest knapp I could get for that table, cause I wanted a soft surface to put fragile instruments on, so as not to scratch them. The topside of that table was really chewed up, w/ the veneer coming loose. The table can be taken down if necessry. My work room is only 10'X15'. For now, it was the easiest fix. Down the road I will have to try it w/o the carpet. Thanks for the tip.

The bad news is, that even though I measured for total thickness of .150" for the perf (Martin 5-ply @ .070") and binding (.080"), and used the .150" Stew-Mac BB, there are certain areas where there's a slight gap (.01"-.005") between the purfling and the binding, more prevalent in the waist. There'e also a couple of places where the purfling is a little squirrelly in the slot. I am hoping the gaps will fill in when glued & be OK. As well as securing the purfling?

Thanks Again for everyones suggestions & input...
Now, on to the back!
Rich ~



Author:  RichB [ Thu Apr 20, 2006 2:35 pm ]
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[QUOTE=ToddStock] Double bearings...(say it with me now)...double bearings. Don't run a ball bearing guided bit without. [/QUOTE]

I gave this much thought Todd. It certainly seems like it would give one the added safety and security knowing there's plenty of support. But, I don't think there's enough room to stack on another bearing onto the shaft where I screw the allen bolt onto, that holds the bearing in place on my 7310?
Author:  Serge Poirier [ Fri Apr 21, 2006 8:12 am ]
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All great tips here guys, thanks!
Author:  guitarjtb [ Sat Apr 22, 2006 11:35 pm ]
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I read through quickly, so this may have been covered by others.

Make sure all the imperfections have been sanded out of the sides prior to routing. This is the guide for your bearings and even a small imperfection will show up in the routed channel.

Flush trim the top or back prior to routing the binding channel. After you have flush trimmed, and have no top hanging out unsupported, you can rout the binding channel in one direction without tear out. This is assuming you have a good bit. I go clockwise in one continuous pass.
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