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I'm ready to close the box of a sinker redwood topped OM. Redwood can be brittle and I'm scared of chipping it as I trim the excess and rout the binding channels. I plan to put a coat of shellac around the edges and take it easy. Do you have any other advice to prevent chip out on this top? This is my first with a redwood top...
Thanks,
Steve

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Steve Sollod (pronounced sorta like "Solid")
www.swiftcreekguitars.com

Follow the routing pattern of routing from high to low like the stewmac web site and numerous others show. If you look at the grain of the wood you will see that this method will generally chip out to the waste. Also chip out happens where the glue joint to the rims is not that good.

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http://www.Harvestmoonguitars.com

In addition to what John says, I like to trim down the areas of excessive overhang first with a small plane or chisel. You have to be very careful not to gauge the sides when you do that. Then when you go with the router make very light cuts.

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Joe Beaver
Maker of Sawdust

Yes, light cuts. The last time I did it, I even pre-scored the edges of the planned routs with a gramil tool. But that can be a problem, too, as your gramil blade must be very sharp and you must take several light cuts. And, of course, you must practice with the gramil before hand. So maybe that is not the best approach for you...or for me, as far as that goes. Whether you use a gramil or not, follow the routing pattern given above. Light cuts and a sharp bit, working your way into the full width of your binding slowly.

Add my vote for all of the above. Lately I've been using the gramil as described and have been pleased with the results.

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George :-)

Help me understand the importance of using the router in the broken tracks, instead of just going around all at once. It seems to me that the router is whipping around at 30,000 rpm and it doesn't know the difference which direction it approaches the grain. The cut of the router blade is still oriented that same way regardless if you approach from the left or right. When cutting with a knife, chisel, etc. it does matter.

PS don't forget the down cut spiral.

I've wondered about that as well. Or rather, why bother ever going counterclockwise? The sections where the router bit's rotation is cutting with the grain should be fine whichever way you're moving, so if the sections where you're going against the grain have less chance of chipping if you go clockwise, then you might as well go all the way around in one pass that way and be done with it... right?

I think we are talking about two separate steps here. The first is to flush trim the top and back. I do that with a typical flush cut router bit. I don't have a down cut end mill to use for that. And yes, the router will seriously grab and splinter the wood if you go the wrong way.

The next step is the binding channels. I use a router bit with bearings. Again, it should be moved in the clockwise direction.

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Joe Beaver
Maker of Sawdust

Climb mill the total edge.........! Then the cutter can't get under an edge to cause splintering.
Tom

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A person who has never made a mistake has never made anything!!!

I just did my first top... LS redwood and i was petrified!! It was all done in one pass. I drew the direction arrows on the top so i wouldn't forget, but the pattern AL uses if different that what is shown in the above images. If i rememeber correctly (I may have blanked that traumatic event out of my mind) the pattern I used was this: Starting fromn the shouders the arrows go in two directions outwards from the shoulders. Same thing on the lower bout. Found a picture...



I think the main thing is to use a sharp bit. I had no issues and it went like butter. Anxiety faded after the first cut. Enjoy!

EDIT: Not really all in "one pass". A seiris of short cuts "To depth". I did not do multiple cuts to get to the final depth. Rob

Ok, i just realized the pattern i used is exacly the same as those photos but i just didnt realize what i was seeing. The first image is what i did and the second is just a pass all the way around to take off the remaining sections.

I can see the advantage of a single smooth pass in the second direction rather a series of cuts. The scary part is putting the router to the wood. So that long pass eliminates a series of tool touches. I suppose i'd be a bit worried about the second pass going in the oppisite direction even though the wood has already been removed, but that's probably just newbie concern...

The illustration in post 2 and the arrows indicating direction of cut on Rob's picture are actually pretty similar, but the single full pass around the instrument in the first illustration is only safe as a shallow final pass, either when cutting the plates flush to the sides or a binding ledge, or tear-outs are likely to happen. For trimming the "overhang" the overhang with a series of shallow passes with a flush trimming bit, Rob's picture shows the safest method IMO.

Redwood is pretty brittle and prone to chipping out, so a very sharp bit and shallow passes is a must. For the binding and purfling ledges, I use the SM binding cutter set, and I clean the bit and hone it well before using it on this wood. Without a very sharp bit, the bit will compress the wood slightly before cutting, and the edge will not be clean. This is most noticeably in the "problem areas" in the prufling ledge, and shows even more clearly when you put a glossy finish everything, and it is too late to do anything about it... So take the time to get it right the first time, it is much more trouble to fix it that late in the game.

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Rian Gitar og Mandolin

My take on the Stewmac diagram is as follows:

The four clockwise cuts illustrated in part 1 of the Stewmac drawing are "climb" cuts, and greatly reduce the chance of splitting. The risk with a spiral cutter should be much less, but with the bearing bits sold by Stewmac and LMII the damage to the top can be severe, even with a very sharp bit. Things happen faster at 30,000+ rpm than they do with a chisel.

You should be able to safely run a clockwise "climb" cut around the entire perimeter, BUT the rotation of the bit during the cut will tend to "push" the router away from the guitar. During the second, anti-clockwise "regular" cut, shown in part 2 of the drawing, the router is "pulled" toward the guitar. Doing this second cut around the entire perimeter is intended to clean up any unevenness in cut depth during the climb cut.

If you don't mind a slight detour, Arnt, you mentioned honing the router bit (cleaning is easy enough). Can you explain how you hone the bit. I have tried just hand honing on a wet stone, but I find the bit really hard to hold and haven't been able get an edge that I am happy with.

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Kevin Mason
Mason Guitars and Ukuleles on Facebook
http://masonguitars.net

I know some folks use those small diamond hones for stuff like this, and take the hone to the bit. I like to just use my regular big DMT hone, on the table, and hold the bit with my fingers, and hone away. Fine stones are about right, perhaps medium if its in bad shape, any coarser can chip out the edge on carbide edges, or so I've heard. Of course, you should only hone the inside edge on the cutter, and since the "gullets" (if that's what they are called on router bits?) are pretty large on these cutters, there should be plenty of clearance for the hone. Just inspect and feel the edge as you sharpen it, you can tell when its sharp.

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Rian Gitar og Mandolin

For Rob's top we used a bit I just got: a 1/4" spiral carbide bottom bearing flush cutter. NOT cheap, but boy does it work nicely!

Another thing that helps is to dampen the top on the upper part of the right shoulder, and lower part of the left hip. If you think about it, these are the spots where the rotation of the router is in against the grain, trying to drive the chips in. If you're going to get a serious explosion, these are the likely spots. Dampening the wood a little bit (a light spritz just before you rout) makes it less brittle.

I've cut binding channels on 3 guitars without following the high to low pattern and never had any problems.
Must be beginners luck so in future I'm going to follow that pattern.

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We are all in the gutter but some of us are looking at guitars.