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On the advice of Mr. Keller in the Kit Build thread, I am adding this question to the Gtr Blding Forum.

New to the forum, so thanks in advance and appreciate your patience.
I’m in the middle of my second acoustic build (Martin D41 kit). I’ve done a dozen electrics and felt it was time to risk “real” guitar building - just didn’t want to spend months on something and then want to burn it in the fireplace. My first was a StewMac 000-28 SP (12 fret) that came out great sounding and a bit lacking in the finish. Mostly the binding was a problem - uneven and a few small errors. It was simple white ABS binding with b/w/b purfling on top, no purfling on back.
Anyway, as most will know the D41 has much more purfling - the materials I received require a purfling channel on top of 0.3” for the 2 b/w/b/w/b sets plus the abalone (plus 0.07 binding). The back need a total of 0.25” for purfling plus binding.
So…. The StewMac binding bit kit doesn’t support. I can scrounge around my shop and grab other bearings (have a few 0.375” as well as a larger diameter 1” bit) and make it close, but it seems I’m missing something.
Is it simpler than I’m finding or does the “normal” binding but sets not accommodate the larger width purfling needs?

Adding the rosette design to amend the post - as I believe the purfling should augment this design.

Don’t know about the binding bearing sets, (my LMI one only goes to .230), but maybe this will help with uneven bindings.

It’s important to sand the sides flat before you route your final binding channels. I route off the excess overhang with a .060 x .230 channel. This is helpful as it means when you’re flat sanding the sides, you don’t have the endgrain of the top and back to deal with. It also means that the bulk of the wood is already gone when you’re routing your final channels, helping to get a nice clean cut, as the final bits are hardly doing any work…

warning
not all bearing set are the same . Do not start with the binding channel until you have done some test fitting. Some bearings are thinner and if you do the binding channel first you will have a very small lip to ride. I can't stress enough TEST CUTS FIRST
you can use tape to help tweak things. I also like to set up the cuts so I am flush or just a few thoudandths of an inch below the sides. It is so much more easy to sand sides to the binding than scrapping.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

thanks. Fully understand and agree on both test cuts and proper prep. Also, from my first build, I like the idea of slightly “proud” sides vs. binding (getting the white binding clean through scraping, then sanding the sides seemed to introduce constant RW dust into the white binding)..
I’ve asked a buddy who has a D45 to send me detailed photos of the top and back bindings so I can compare with the kit materials Martin sent me. I might just not use one of the b/w/b strips to get the channel down to something both manageable and within my bit set capabilities.
again, thanks much.

The other thing to keep in mind when doing wide purfling channels is you may have to make another "donut" if you are using a binding jig. I made an Oscar Schmidt inspired Grand Concert that had very wide Purfling channels. John Hall made me a donut that had a bigger hole, and I used - I believe - a .375" cutter (the cutter didn't fit in the donut hole of my standard donut).

A D-41 uses two x THREE-ply BWB purflings bracketing the shell. Assuming a 0.036 BWB, that is a binding/purfling stack of .060 binding, 0.036 BWB, 0.063 shell, and 0.036 BWB. That's a 0.060 binding channel and an additional 0.135, or a total width of 0.195 for the total stack if you are using CA, and about 0.200 with allowance for glue (4 x 0.0015). Both LMII and StewMac binding cutter/bearing sets will do that width without issue.

A five-ply on each side of the shell will look weirdly busy, or maybe like one of the plainer Bozo's I've seen. OK - Bozo...still weird, but I like them.

_________________
A constellation only takes shape when one maps the whole.
- Beth Brower

The D41 kit has a wider rout in fact most martins are wider than stated always rely on measuring the binding and purfling included in the kit. The old pre plastic days the purfling were smaller the top pearl is .0625 the poly is usually .065 from martin but measure to be sure. Bindind is .0625
Martin kits also may vary from actual spec

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

If you read through Longworth's book you see where Martin varied the specifications on the same model throughout the years. As woods and decorative materials become more or less available Martin would switch to something else. I think in some cases an iconic instrument gets measured and documented and for the copyists that becomes the only way to authentically build that model.
I do like to copy the shapes and sizes of the various Martin models in a general way - I think they are well proportioned and look nice, but I don't worry about the minutia.

as a repair shop I can see at least 4 different changes the old wood purfling was the thinnest.
it also looked rough compared to today s standards. In the early days a lot of the pearl work was farmed out

then as the wood was phased out there was the fiberloid plastic this was later in the 30's
then the plastic changed again when the celluloid replaced the fiberloid and once again the ABS
when it replaced the celluloid. The ABS is the wider of them all.
So pick and era and go with that.
I like the wooden era and use that on my pearled guitars.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I agree with Mr. Hall - the fiber and wood purflings, as well as solid (versus laminated or veneer on plastic) shell always looks better. The vinyl junk that Martin has used is just that - terrible to look at and to glue.

Keep in mind that milling binding channels at the net thickness of modern 0.063 binding means that final scrape and prep for filling, etc. removes both binding and side wood... it's easier to mill the channels for grained celluloid at 0.060, then scrape the 0.0025 worth of plastic off down to the sides (which were already blocked and should be true prior to milling the binding and purfling channels). All that old celluloid has shrunk up by a few thousandths anyway, with the 1934 000-18 shade top binding I was measuring yesterday running well shy of 0.060. This guitar is really not an exemplar of mid-to-late 1930's 000's as it was really the tag end of the OM production (long scale, bar frets, ebony fretboard and bridge, but with celluloid binding that was introduced in 1934!)... Martin would change scale length, fret config, materials, etc. not long after this 55xxx serial was built.

On kits: we saw a variety of kits and kit builders at Greenridge... usually to fix problems with poorly-bent sides, incompatible components, or just to cheer-lead a bit through the tougher parts. The materials varied from what we would have used to whatever was available and cheapest off Alibaba. While a pre-milled set of rosette channels more or less locks you into whatever the kit provider sent along, you always have the option to upgrade provided the materials will fit. Same with binding. As your parents likely requested, just make good choices.

_________________
A constellation only takes shape when one maps the whole.
- Beth Brower

Has anyone ever noticed any tonal differences in the widely purfled highly Abalonied Martin’s vs. simple narrow purfling like a D28?

I have always felt like the peripheral attachment of the top to the rim was kind of an important joint and having purfling that almost extends past the lining leaving only a thin wafer of wood as an attachment seems intuitively a bit sketchy.

I like to do the final voicing of a top after the box is closed but before binding, by thinning the edges in the lower bout. (A la Dana B). As a consequence I just use one 0.060 bwb for top purfling.

Any Martin experts care to comment? Maybe I’m all wet.

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

NO
some people will differ I do not hear a difference it is just pretty not tonal.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Everyone, thanks for all your advice. I went with a simpler bwb, abalone, bwb format. It’s possible the martin kit wanted me to use the other bwb strip as an add below the side binding (not sure - kit plans devoid of detail unlike StewMac). But it looks OK and since this may be a kit but its “my” design.
FYI, I didn’t refine / thin any of the ABS purfling, but the 2X bwb, 0.063 teflon strip plus the .060 (measure nearly 0.070) binding all in measured over 0.230 (north of my StewMac bit capability). Did a few wraps of tape on test pieces and dialed it in.
Trying to add the finished picture. Thanks again to all. Next question involves grain filling rosewood or not?