WBO 2024: Bari-metric Pressure

[Bruce Johnson]

That's normally how I'd have done it (and I do the lap joints on some of the gates I've built the same way), but I wanted to see what the advantages of the forstner method were (if any). Learning experience. It saves wear on your router bits; that's about the only takeaway I've really acquired -- although, as I said to Gary, I don't think it particularly adds up. As a technique, it has the feel of an artifact from an era when router bits were more expensive and there was less access to decent carbide.

Yes, in my experience, Forstner bits are just about the fastest way to hog out a volume of wood, particularly a hard wood like maple. But does it actually pay off in time savings when routing chambers in a body? Usually not. It's faster overall to just rout it all, in multiple shallow steps. Pre-drilling starts to pay off when you need to rout really deep, like 1 3/4" deep mortises.

I did a thread on here a while back on the subject of "wearing out" router bits. It's actually very difficult to dull the cutting edges of a carbide router bit, doing the level of routing work that we Luthiers do. When a router bit starts looking ugly, smoking and barely cutting, it's just coated with baked-on varnish. In almost all cases, the cutting edges are still sharp and fine under the goop. Clean off the varnish, and it'll be like new. In the thread, I show my technique of quickly cleaning off the varnish without damaging the sharp edges.

https://www.talkbass.com/threads/router-pattern-bits.1330464/#post-21016969

 

[Flying B]

I agree, and I've used the technique myself, but I do think it is overrated and very slow. I find it much more efficient to just make multiple passes with the router. More wear on the router bits? Sure, but I'm not sure that it matters or that I care.

The build is looking great!

Agreed, I've used the forstner method in the past but just went straight in with the router on my current build and it was quicker and easier. It does help if you have a short template cutter to start off and then a longer one you can switch to to get the depth, otherwise you end up needing a very thick template to start off.

 

[Quills]

That's a great post, Bruce. I've cleaned them with brushes and solvents before (white spirit / mineral spirits for light resin buildup, paraffin / kerosene if it's serious), but have stayed away from the diamond hone. I should definitely try it as a couple of my bits are long in the tooth.

I do a lot of stuff with hand tools, too, so I don't even go through them as quickly (slowly) as some people might.

 

[Bruce Johnson]

That's a great post, Bruce. I've cleaned them with brushes and solvents before (white spirit / mineral spirits for light resin buildup, paraffin / kerosene if it's serious), but have stayed away from the diamond hone. I should definitely try it as a couple of my bits are long in the tooth.

I do a lot of stuff with hand tools, too, so I don't even go through them as quickly (slowly) as some people might.

Yeah, the only way to dull a carbide router bit is with a hundred hours of high-horsepower cutting of abrasive wood, like particle board. Our work of making feather cuts in hardwoods is nothing to a carbide edge.

In my 30+ years of Luthier and small-shop routing, I don't recall ever really dulling a carbide router bit. I've chipped a few.....

 

[Quills]

Very minor (and very silly) update.

None of what I had planned for today happened. The proverbial visitor from Porlock showed up and delayed me until there was no point starting anything because shopping was getting delivered, which delayed me until there was no point starting anything because I had to go and get a prescription which delayed me until ... until ... until ...

However, I managed a quick scurry to the shop for an hour this evening. I did some prep work on the sycamore (maple) top -- mostly sanding (no pics) and tidied up the mess from yesterday.

With respect to the broken locating pin, it occurred to me last night that I could just locate the template on the other two pins and drill a new hole next to the previous one to re-create the third pin. And then I realized that, despite them only being 2mm (5/64") I could probably just extract the pin and replace it -- they're not glued in.

So I took a fresh cocktail stick and caressed the sharpened end with p120 sandpaper; then took an awl and indented down as close to the centre of the 'pin' as I could manage; then dipped the cocktail stick in a drop of high-viscosity CA and wiped it off leaving only a thin film; then speared the glue-coated end down into the indent and left it there for two minutes. Worked like a charm ...

Fresh reinforcements ready for action ...

While it's a worse day weather-wise tomorrow; they're still scheduling no rain, so hopefully I can just move today's plans into tomorrow.

 

[lbridenstine]

I think for me, the sound of a drill press is less obnoxious than the sound of a router for the time frame, and the router makes more of a mess. That being said, I still get annoyed with how long it takes to hog out wood with forstner bits.

 

[Quills]

I think for me, the sound of a drill press is less obnoxious than the sound of a router for the time frame, and the router makes more of a mess. That being said, I still get annoyed with how long it takes to hog out wood with forstner bits.

That's valid. It is a calmer experience. But so are hand tools.

 

[lbridenstine]

That's valid. It is a calmer experience. But so are hand tools.

Definitely.

 

[Quills]

Four steps forward; one profoundly-annoying step back.

I started today's work by cutting just outside the body outline on the bandsaw.

I then tried to piece together the cuts for an artsy shot, but gave up halfway-through as it was too much like doing a jigsaw (that's what happens when you use 3/8" (9.5mm) as your default blade size rather than 1/4" (6.4mm)).

It came out pretty decently, though ...

... except ... I found one section where the walnut lamination hadn't completely stuck down (which was disappointing as the rest of it was immaculate):

I ran an x-acto #11 through the slot to get an idea of how deep it went and to try and clear out any debris. It wasn't too deep, so I pulled some p120 sandpaper through couple of times on both sides to give it some tooth, cleaned it out with the knife again, wicked a whole bunch of low-viscosity CA into the slot and clamped it hard shut. I didn't worry too much about clean-up as the entire outer shell was about to come off.

It seemed to work and hasn't given me any problems yet.

The above having been sorted-out, I found to my dismay that the wind was much higher than forecast and, in the process of getting set-up outside, the extra chill was causing concern, so I made an arbitrary decision to move everything indoors.

It somewhat turned into a blessing-in-disguise as I've figured out how to safely lock down the large router platform (using three pieces of 3x2, a vice, two clamps and the height-adjust-from-below feature) so I can use it indoors -- with the shop vac, which simplified clean-up.

With one major exception, the rout went pretty well:

I put a Saint-Leo-approved 7/16" roundover on the back as I realised it would be harder to do freehand after the control cavity was cut.

There was just one catch. Literally. I mean the workpiece caught once -- and, while it could be worse, it's also super-irritating. I was doing everything correctly -- only routing downhill, using the double ended bit to it's full potential etc. -- but still ... endgrain ...

I'm not quite sure what to do about this. I mean: it would be trivial to fill it and sand it back, but the question becomes 'what then?'. Do you try and match the fill as close as possible and leave the wood fully visible? or do you accept that it's probably going to be noticeable and dye / paint the body (I was going to pore / grain fill anyway, so the finish was always going to be smoother than straight grain)? Or: do you re-shape the body to sand it out? It's on the lower horn, which is at least one of the more customisable parts of the shape and, despite the exaggerated perspective of the close-up above, it only goes in about 2mm, so a re-shape is eminently doable.

If you're trying to keep the wood visible, the smart money says: try and fill it as inconspicuously as possible and then re-shape if it doesn't work. If you're not trying to keep the wood visible, it doesn't matter. I'm going to have to take a moment to figure out what I want to do, which is fine because there are tops, control cavities and, most importantly, necks to worry about in the meantime. My inner Hicks is leaning towards reshape, though; nuke the site from orbit etc., but I'm conscious that this could just be a short-term reaction.

Despite that, I'm still moderately happy with how it went and where everything is; I just need to figure out the preferred plan of attack.

To be continued ...

 

[Flying B]

I'd just sand that out, I don't think it would make an appreciable difference to the shape.

 

[Quills]

I'd just sand that out, I don't think it would make an appreciable difference to the shape.

Agreed. That's where I'm increasingly leaning. I realized after I posted that I need to figure it out sooner rather than later as the top gets flush-trimmed to the body.

 

[Quills]

Top be or not top be.

I got tired of jerry-rigging various clamping cauls and, after a concerted search could still not locate my oak ones (I suspect they're at my folks' house or someone's had 'em away), I decided that the cost of a quick trip to the hardware store and a few shekels was worth paying.

I bought a 2.4m (8 foot) length of 45mm (1 3/4"-ish) square SPF and cut it into four 525mm (21") lengths plus some change. I drew a line roughly 4.5mm (3/16") from the edge to give me something to coordinate from and, using the step-back planing technique, put a 'digital camber' (it's not really a curve, more an approximation using straight lines) on one edge of the boards with a jack plane. I then put some 50mm (~2") packing tape along the cambered edge to resist glue and locked the packing tape down at the ends with masking tape.

This picture gives you an idea of the 'camber' on each caul. Bear in mind when they're used in anger the camber will be essentially doubled, although I can also put packing tape on the opposite flat edge and clamp camber-to-flat if needed.

I tested them opposing and thankfully they're still flexible enough to be clamped totally flat.

I then broke out the horizontal belt sander and, using p150 and then p240, 'fixed' the catch from the router-table-ing shown in the previous post. You can get an idea of how much had to come off from how much of the 7/16" (11.1mm) round-over got removed. In practice, as Flying B guessed, it wasn't much. I overlaid the template on the body and the removed area was less than 0.8mm (maybe 30 thou / <1/32"). The shape isn't detrimentally affected at all. Pretty happy.

Obviously, the round-over's are going to have to be re-routed at some point, but I'm going to save all of that until the body's mostly constructed as it can tie-in with the final sanding passes.

I then jointed the sycamore (maple) top and marked it for correct alignment with the grain pattern. Tangentially -- and I'm sure you'll agree that this is critical information -- the blob of stuff visible on the outside centre-left of the boards is a sneeze-bogey which somehow missed the tissue. I clearly took this pic before I cleaned it up.

I used the stretch tape technique to aid with clamping and alignment, and used the neck blank to provide a suitable angle:

After that, there was only one thing left to do. One more time, with feeling:
# ... moon doth rise ... dragon's face ...
Clamp-HENGE!

There was an interesting moment in that, when I went to feel the alignment, everything seemed to be 'in' pretty darned well except one 1.5 inch (40mm) stretch a little way behind the rear caul set that was slightly high between two flat areas. It perplexed me for a minute or so as 9.5mm (3/8") sycamore isn't usually that supple. Clarity came when I felt the other side of the joint and found it was also slightly off; on the same side. There must have been one area of the board that was thicknessed slightly fatter than everything else. Fortunately, they're within easily-scrapeable parameters.

TBC.

 

[Quills]

Not too much on the build today as I don't have much shop time available.

I went out this morning to take the glue-up out of clamps. The glue-up went really well -- those cauls were a good idea; the planar alignment was about as good as possible. I took out the slight thickness variations and excess glue with card scrapers until the seam was flush. There's still some excess glue staining in one spot, but I think it might be outside the body contour, so I'll worry about it when I get there as I dont want to over-scrape / sand at this stage.

The sycamore is nicely figured, but it's relatively mild figuring (you can barely see it in the pics above -- although that's partly a phone camera dynamic range issue). The fact that it's a wild sycamore and not a 57xAA top sort-of appealed to me when I had the idea. So I then put a thin layer of white spirit / mineral spirits on the surface to get a handle on whether it was worth trying to pop the grain and dye it.

I'm going to go with a slightly-more-than-tentative 'yes'. There's a slightly barren area round about the front pickup zone, but the waists are in that area too, so it wouldn't matter as much, but might be cause for some kind of darker-edge burst.

 

[Quills]

One-way ticket.

After thinking about the build yesterday, I realized that I was on the verge of a (minor) order-of-operations error. The top needs to get flush trimmed to the body, so I couldn't defer edge-sanding of the body until later (I mean: you could, but then you'd be increasing your work in sanding everything). On top of that, there's more routing coming and that needs to get done before the body carves, so the edge needs to be 98%-there at this point.

So I started today's work by sanding the edges with p240 on the OBSS and a p180 sanding board. I'll probably have to re-rout the round-over, but I was going to have to do that to deal with the catch anyway, and most of it's already been taken off.

I also couldn't defer dealing with the control cavity until later as, with the top glued on, it gets trickier to rout and do the rebate for the cover (not impossible; but, again, more annoying). So I took the forstner bit I originally drilled the holes with, moved it away from the corners by a couple of mm (5/64"), and used it as an awl to mark drilling locations.

I then drilled through those indents with a 2mm twist bit in the drill press. This allowed me to take a forstner bit that was 2mm smaller than the original and drill through from both sides in the hope of keeping the holes clean. I had a slight amount of tear-out on one hole, but it's inside the extents of the cover rebate so it should be fine.

As you can see, I marked the outer perimeter as a do-not-exceed line and chopped the inner piece out using a jigsaw.

I then semi-inverted the trick I did with the template and the edge-rout, although this time I was going to use the top itself in that position instead of the template.

I took the template and carefully matched its centre-line to the centre-line of the sycamore top (in the position where I thought I'd get the most decent amount of figure); then clamped it in position.

I took it over to the drill press and used the locating pin holes in the template to (hopefully) perfectly line up a 2mm drill with with the top underneath. I then started the drill and went cleanly through the extant holes and drilled through the top below.

So now the locating pin holes should be in the same relative place on both the top and the body.

While the template was still in-location on the body, I could then mark out the cavity locations so as to know where they were (or, more importantly, where they were not) for clamping purposes. I started to make what could have been a somewhat-serious mistake here, but I think I caught myself before it got too bad. Can you tell what it was?

After cutting the top to rough outline on the bandsaw, I then took the ROS with p120 and sanded both of the mating surfaces to clean up handling dirt/grease and add a bit of tooth to the scraped sections. I then gave it one pass of circular motions with a p80 sanding board to add a little more tooth.

I then taped the edge of the joint on the body side as closely as I dare to reduce the impact of squeeze-out on the future flush-trim operation ...

... and after cutting and installing fresh locating pins for the body holes ... for possibly the final time on this project ... you know what it is.

Clamp.
Henge.

The glue-up itself took over twenty minutes, mainly because I was trying to stack as many clamps as possible into a relatively small space while preemptively mopping up excess squeeze-out from the tape. I cut a new caul to get pressure on to the inner 'block' structure (you can see it in the background of the 'tape' picture above), as many of the clamps couldn't reach in there, but the new curve-cauls could, so it should be ok.

Schroedinger's clamp-up. Right now it's both amazing and abysmal. We'll find out which (or where on the continuum between them) it is tomorrow.

 

[Beej]

I routed for pickups on the back of a guitar once. After an enormous amount of work to get to that point. Some things may have flown across my shop with 'uck' (or something similar) reverberating through the neighbourhood.

 

[Quills]

I routed for pickups on the back of a guitar once. After an enormous amount of work to get to that point. Some things may have flown across my shop with 'uck' (or something similar) reverberating through the neighbourhood.

Ouch.

Funny thing is: today, after I punched the forstner holes in the back, I had a panicked 6 or 7 seconds where I was absolutely convinced I'd put them through the wrong side. It's because they looked like a control layout, I think (because they're a mirror of the front). I even got the point where I was figuring to rout a rebate and put a control plate / non-scratch-guard in and that maybe front access wouldn't be so bad, but fortunately I realized that they weren't what they looked like and that they were supposed to go where they were.

I have genuine anxiety of doing something stupid on auto-pilot. It's eminently possible.

 

[Matt Liebenau]

I’ve done something similar although, fortunately, recoverable. I have one bass with control cavity covers on both the bass and treble sides of the back. Thankfully I caught it and only the correct side actually has pots going through. It’s lightening. Yeah. Lightening.

 

[T_Bone_TL]

It’s lightening. Yeah. Lightening.

<Mad evil scientist cackle on> ...and the minaturized Tesla coil we installed in the "spare" control cavity gives us lightning, when guitarists crowd our stage space...<Mad evil scientist cackle off>

 

[Matt Liebenau]

<Mad evil scientist cackle on> ...and the minaturized Tesla coil we installed in the "spare" control cavity gives us lightning, when guitarists crowd our stage space...<Mad evil scientist cackle off>

Oooo! A big, sparking Tesla coil would even put me ahead of Ace!

 

[Quills]

Quick update.

The de-clamp went well, as did the glue-up, for the most part (mild foreshadowing).

Once I got the body out of clamps, I ran it through the small router table with a flush-cut bit to tidy-up the top. As is semi-traditional on LC, I then went inside to weigh the most-of-the-broadphase-done body.

Some of you may remember, in post #6 I said:

I could also have been more aggressive with the cavity size -- they could be larger but it's my first complete build and I'm trying to stay away from the carve areas (arm rest / belly contour), the edges and the centre block. It being a baritone and that I'm probably going to put fat strings on it at some point, I'm being conservative with the safety margin. I'm also not super-concerned about weight; my main 5-string is over 10 pounds.

Well, it's a good job I always felt that weigh -- I mean way -- because a big-booty'd body with African entandrophragma only means one thing:

For those who can't make it out, that's dead-on 92 ounces, which is 5 pounds 12 oz, aka 2.61 kilos.

The neck and belly carves have to come off, as does some extra contouring and the pup / neck cavities, but all the hardware has to go on. PAFs are about 150 grams each, so that's 2/3 of a pound for the pair. Conservatively call it a pound and a half (700g-ish) for hardware, with maybe 6oz/170g max coming off; that's 6 lbs 14oz (3.1kg) total on the body. It's going to be a push to get it under 10lbs (4.54kg). At the moment, I'm targeting mid 9s, but that's optimistic; the hardware load on the body is probably a bit higher than 700g now that I think about it. It's all good, though; as long as I can get it under 11lbs, I'll be happy.
(This paragraph was brought to you by the metric vs imperial thread of last week).

In post #7 I said:

The body blanks were taken down to 35mm. In combination with the sycamore top and the walnut lamination, this should leave the body at around 47mm thick.

Close, but 0.5mm shy of a cigar:

The only issue with the glue up was that there was a section -- annoyingly along the top of the guitar, right where the player has to look at it -- where there were intermittent gaps between the maple and the walnut. The maximum was a little under 1/64" (<0.4mm) wide. This is by far the worst bit (most are at most 1/3rd the size):

I got clamps on it to see if it moved (to perhaps clamp it down); it didn't budge at all. I then got a feeler gauge and an x-acto #11 in there to see how deep the gap went. The deepest point was barely over 1mm before hitting solidity. I suspect what's happened is that I may have dawdled too long on that edge with the ROS and the edge got slightly rounded, which has essentially left a shallow chamfer that can't really clamp down.

All is not lost, as there is going to be edge-contour routing occurring anyway and the intention was to take it to the bottom of the walnut. It's possible that I may have to go a little lower, but the point is that it may mostly clean up anyway during the contour. Fortunately the very worst part (above) is right in the arm rest carve, so that's probably coming off regardless. It should also be pointed out that the gap is tiny. It's almost at the point where you could just fill it with finish.

Because I wanted to see what happened if it didn't clean up, and because I need a smooth surface anyway to coordinate from, I decided to grain-fill the gap, just to see what it would look like, so I taped it up and packed some water-based filler of the appropriate light colour in there:

Everything that's listed above I did this morning, before work. This evening I took the tape off and sanded back the fill, just with p240 -- nothing serious, to see what it looked like. It's OK. If that's the worst that it's going to be, I can live with it. I'm still hoping it tidies up a bit.

Message ends.