ESP M-II type "Invaders" Superstrat

[Prostheta]

Sighting down the blank, there is a marginal tilt towards the left or the headstock tip which will work in my favour as discussed. Literally a fraction of a degree.

[Bizman62]

23 minutes ago, Prostheta said:

I would have preferred to use small panheads or maybe add washers so the countersink profile doesn't encourage splitting.

Heh, exactly my thoughts as I looked at the picture before reading!

[Prostheta]

Those screws are fine since the thread is 3mm. As long as they seat within the upper pilot and have the right bite within the lower one, they're okay. They were just cinched down so the heads sit flat enough so the pieces can't part. I hate those screw heads anyway....a Torx screw would be much safer both for insertion and not stripping out on removal.

[Prostheta]

So this planned out perfectly. Note that the centreline on the headstock part of the Maple deviated at a very slight angle from the body part. The centreline was extended down the headstock by eye. This isn't easy, however a piece of blue tape provides a high contrast "target" so you can tip the blank up and down to sight whether it's to the left or right of centre. Moving the tape and repeating until you're on the mark isn't too tricky once you get a feel for it. Over such a distance, any error is in the magnitude of a mm or two which can be borne in mind for any futher calculations made around the headstock. Once it's on the CNC, it'll be what it is with reference to the edge (57,5mm parallel off the centreline) however it's enough that the wing tip glueing can be considered. The neck portion of the blank measures 25mm in thickness and the headstock 26,4mm. The final thickness of the neck will be brought down to 21mm on the CNC (after a bit of mass stock removal on the jointer) which will advance the neck to headstock transition line a fair distance (4mm of depth at 13deg is 17,3mm if you do your trig). the headstock itself will only receive a skim cut to establish a plane referenced to the CNC. It's safe to say that the transition will move about 15mm along. This needs to be considered if I am to glue on a piece before the CNC gets its teeth into there. The overly-thick headstock is good for the moment, since it helps with stiffness during initial machining. The first neck process showed that the headstock wanted to bend under tool pressure. This isn't an option. I may still figure out some sort of auxiliary workholding jig that supports the headstock from underneath, however I'd want to make that adjustable rather than a one-shot jig.

[Prostheta]

I should probably pick up some fresh sanding drum sleeves in coarse and medium grits for surfacing the back of the headstock, and also plan out how that diameter works with the volute. Unlike volutes that have specific purposes - such as providing strength behind a truss rod cavity access point - this volute is largely cosmetic. Thicknessing the headstock with a spindle sander fence will have a "flatness target" just beyond the first tuner's screw location, and from there it becomes a more manual task to shape in the rise.

 

I also decided that I will approach the fingerboard differently for a few reasons. Firstly, I want to cut/bind/radius/inlay/slot it off the neck. In principle this can all be done by taping it to an MDF board. This reduces the issues with repeatability mentioned previously which is the best guess I have as to my original offset problems. Human error is always the first call when errors occur, however I still have no good answer why that went tits up. It does push me towards reducing repeat cycles on the same part, or at least factoring out errors between them as much as possible.

So, before this the Ebony fingerboard blank will be run over a jointer both face and edges, then through a thicknesser. To eliminate any possibility of snipe in the glueing face, I will (try and remember to) glue service material either side of the Ebony. Essentially these are strips of random wood longer than the piece you want to protect that are the same thickness. The planer's infeed roller "takes up" the service material first when feeding the wood in and feeds out with its trailing edge. This way any snipe that occurs during infeed/outfeed is offset to the service material than the workpiece itself. Service material can be attached with superglue or even hot melt adhesive.

I've been working on the issues of how to improve the fingerboard inlaying. The epoxy seemed to have sat on a pocket of air in several of the more detailed inlays. The shape of the fingerboard makes it impractical to consider popping it onto a vacuum or pressure chamber, even if I had access to those. A trawl of YouTube revealed a few DIY methods such as using brake bleeding vacuum pumps and "food saver" vacuums. Neither of these will achieve the sorts of vacuum hardnesses that a full-on pressure vessel can, however they may be enough to pull air pockets out and through the epoxy. Primarily, I can reduce the depth of the inlay pockets to 1-2mm which will definitely help. But how to put the fingerboard under vacuum? One video of how to produce a cheap DIY vacuum degassing vessel from a cookie jar got me thinking. If I can't put the fingerboard into a vacuum vessel, can I put a vacuum chamber onto the fingerboard? I've got a few tiny single-serving jam jars which have a diameter of maybe 30mm or so. If I can drill a hole through the base and apply some sort of compressible silicone gasket around the rim, I might be able to hold this over a poured inlay and pull a vacuum over each inlay one by one. Whether this is using a brake bleeder, a mini food bag vacuum pump, my Festool dust extractor or the Venturi at my workplace will be a bit of an experiment. Using what is to hand feels better since it allows more time and concentration. The dust extractor feels like the most convenient (and free) followed by figuring out how to use the Venturi.

Lastly, working the fingerboard off the neck give me the option of making a neck carving jig:

 

This solution is similar, and I like the enclosed nature of the mechanism even though it is more complex and requires additional material such as the Plexi.

 

I don't currently own a router appropriate for that length of bit, however I can certainly borrow one until I do. The profile pucks seem a perfect solution since I am very much a desktop designer, CNC operator and propellorhead, plus it's a good jig to have going forward.

[Prostheta]

Not a huge amount of progress today, however I did joint that edge on the headstock, cut a section off and glue it back in to sort out that headstock tip. The lower part was jointed by running it over the table saw to skim the edge (you can see the path on the neck section). A triangle was cut from the end, then cut parallel to the jointed edge to make it easier to glue. The blue pen line is my cheat for understanding how far along the neck the headstock outline moves when facing off the fingerboard glueing surface (now the final 21mm). I'll face off a fraction of a mm from the face of the headstock once this has glued, however by that point I might as well be cutting the entire thing. I do want to play around with the volute rise as this affects how much material I need to leave on the face of the headstock. The more I surface that (to a point because of the glued wing) the lower the volute can be, but also the closer the scarf join is to the headstock.

[asgeirogm]

Regarding the air pockets under epoxy, I've never done epoxy inlays so I probably don't have the right idea here, but if the problem is air pockets 'under' the epoxy that can't escape as the epoxy is too dense/thick and not bubbles in the epoxy itself, could you make a hole through the inlay through the entire fretboard so that the air will be forced out through the bottom of the fretboard, where you can just close up the hole with some tape and then sand it down? Maybe the bottom of the inlay and the hole could look like a funnel to make sure the air is forced through the hole. Probably a terrible idea but I thought I'd throw it put there.

Another way I've seen discussed that you probably know about already is heating the epoxy so that the bubbles rise out of it, but I thought I'd mention that as well.

Love the design and build btw, an M-II is definitely somewhere on my todo list for the future

Edited September 27, 2021 by asgeirogm

[Prostheta]

Thanks!

There are limitations to how well that could work. My 0,5mm endmills only have 4mm of cutting depth which would mean some other way of cutting through. Additional depth in the pocket would encourage more differentiation between the epoxy and the pigment, which I definitely don't need. The epoxy used for the inlays was super thin casting resin, so has the best chance of allowing trapped air to rise out of the pocket. Yes, I do heat the epoxy to help bubbles to rise. In super fine inlays it don't seem to make much difference to trapped air at the base.

The solution is to reduce the pocket depth to 2mm or so, and also to use some sort of localised low pressure to force air through the epoxy. This might need a bit of "damming" around the inlays so that there is excess to fall back in once the bubbles have risen, but we'll see once I figure out the how-to on that.

[Andyjr1515]

18 hours ago, Prostheta said:

The solution is to reduce the pocket depth to 2mm or so, and also to use some sort of localised low pressure to force air through the epoxy. This might need a bit of "damming" around the inlays so that there is excess to fall back in once the bubbles have risen, but we'll see once I figure out the how-to on that.

I may be mis-remembering this, but I think I've seen someone (I think it was one of those resin-encapsulated dandelion paper weights) use a blanket storage/skate board vacuum bag, simply with a simple cage round the object itself to prevent the bag vacuuming itself to the item.  My recollection was that the air came out like a fizzy drink leaving an airless clear resin block.  I don't think it needed a lot of time with the vacuum cleaner plugged in either. 

[Bizman62]

2 hours ago, Andyjr1515 said:

use a blanket storage/skate board vacuum bag, simply with a simple cage round the object itself to prevent the bag vacuuming itself to the item.

I have similar memories, potentially even from a guitar building video from - dare I say - a luthier with a tattooed head...

[Prostheta]

The damming was more about creating a discrete area around the inlay, so that any air pulled through doesn't simply spill the epoxy over the flat surface of the fingerboard where it won't re-fill the evacuated pocket. A dam should help "provide" enough resin in a pool so that it naturally falls back in. That's my theory anyway. I've seen epoxies that are very gassy rising like a foam, collapsing as the air bubbles break. That rise/fall is where things might go wrong.

[Prostheta]

I took the neck back to the CNC today and performed repeated facing operations on the headstock until it came closer to 21mm in thickness. This pushed the transition between the fingerboard and headstock faces back, and also the outline of the headstock. Juggling jobs meant that I didn't give prior though to the placement of the glued headstock wing tip, so I had to re-saw that off and re-glue in the correct position. Oops. Still, no harm done.

[mistermikev]

5 hours ago, Prostheta said:

I took the neck back to the CNC today and performed repeated facing operations on the headstock until it came closer to 21mm in thickness. This pushed the transition between the fingerboard and headstock faces back, and also the outline of the headstock. Juggling jobs meant that I didn't give prior though to the placement of the glued headstock wing tip, so I had to re-saw that off and re-glue in the correct position. Oops. Still, no harm done.

cnc is really the bass-o-matic of the the tool world.  so many tools it can do the job of!  afa wing tip... if a luthier makes a mistake and no one sees it... is it still a mistake?  also, mmmmmm steak.

[Prostheta]

+1 on steak for the occasional treat

CNC isn't the magic bullet that a lot of people think it is, however it does allow you to re-imagine processes and approaches to building. I couldn't rely on it solely, as my general skills would die a death. It has to be regarded as an opportunity to try things that might otherwise not be possible, or to bend your thinking down new avenues. I love it, especially the 5-axis stuff. Everything needs to be a challenge on some level, otherwise I'm just existing within my skillset and not progressing. But as I said, you can't go 100% CNC otherwise you end up losing many practical working skills by not maintaining them.

[Prostheta]

Neck and headstock perimeter, plus binding channel cut on the CNC. Getting there....must drop it back on at some point to do the headstock logos. This time they'll be just 2mm deep to help reduce bubbles in the epoxy, same as the fingerboard inlays. Must also remember to cut myself a 0,7mm veneer strip for over the top of the truss rod. Dropping it in slightly helps with the adjuster being slightly higher than the top face of the aluminium channel....

[mistermikev]

10 hours ago, Prostheta said:

+1 on steak for the occasional treat

CNC isn't the magic bullet that a lot of people think it is, however it does allow you to re-imagine processes and approaches to building. I couldn't rely on it solely, as my general skills would die a death. It has to be regarded as an opportunity to try things that might otherwise not be possible, or to bend your thinking down new avenues. I love it, especially the 5-axis stuff. Everything needs to be a challenge on some level, otherwise I'm just existing within my skillset and not progressing. But as I said, you can't go 100% CNC otherwise you end up losing many practical working skills by not maintaining them.

I worked as woodworker/solid surface fab on and off out of high school up until 2006... never really touched a router till I started building guitars a few years ago.  just pointing out - was surprised how much was still in my dna, then again I hear ya: I was very timid getting back into it!!

cnc... I was just saying it CAN do any job my other tools can do... not necc that it should or is even efficient at it!

 

neck is looking really great/clean.  lovely.

[Prostheta]

Thanks man, and I agree. The trick I'm trying to work around is the tendency of the path to slow down around corners. Partly this will be down to me converting all curves to discrete line steps which isn't the best for a number of reasons. I do this because the DXF import process imports lines as lines. Curves tend to be re-interpreted, which causes other problems. The biggest of these is the "closed contour loop detected" error. When the CNC throws this one, it's because the DXF import process has created an interstitial move within the path that is smaller than the machine itself can manage reliably. Logically, the machine just stops where it is and keeps the spindle spinning until you manually maneuver it out. How convenient. If I were more diligent, I'd cut air before committing workpieces to the grinder. Unfortunately I never have enough time to be so patient.

[Muzz]

On 9/30/2021 at 4:10 AM, Prostheta said:

This looks sharp and schmicko, looking forward to hearing some heavy tones from this. 

[Prostheta]

#metoo (am I doing that right?)

Just going to the PO (pissed office) to collect my binding and the custom decal sheet. Will report back on that later.

[Prostheta]

The decals look great, however I can see some sort of artifacting which disturbs the linearity of parts of the logo....must raise this with Rothko & Frost....

The transparency will allow the glow pigment to shine through the decal....

 

Black mask, gold drop shadow and silver snow "pixels".

[Prostheta]

Binding. This stuff is excellent. It's the green Incudo ABS binding from Rothko & Frost in the UK. It doesn't react very well to bending, so you have to be very dutiful with heating and moulding otherwise the bends stress and the polymer structure of the plastic alters, turning white. This stuff melts readily in acetone and bonds with it very very well. So much so, it's good enough for the wicking approach rather than using acetone-based gels (Duco) or even melted slurry. The colour is a little pale in the daylight (I would say that this is a little less saturated than in reality) but in artificial light it has a much more primary green going on. Perfect for the implication of the bright-coloured t-moulding that arcade machines used to be bound in (Google it).

The depth of the binding was calculated based on the headstock angle (13deg) and the depth of the locking nut shelf (15,5mm) so that the binding terminated where the locking nut butts up to the zeroeth fret location. I think that this was something like 3,57mm of binding depth, but by this point over such a shallow angle, 3,5mm is fine for precision. A file can fine tune the channel at the ends for visual purposes, and that needs to be done to clean out the binding channels anyway.

[Prostheta]

Well alrighty then. I dropped the neck back onto the CNC and routed out the headstock logos to 2,5mm each then filled each out with casting epoxy/pigment mix. This'll take a few days to chooch, but that's fine.

Bed goes up.

Bed goes down.

Bed goes up.

Bed goes down.

[Prostheta]

So what have I learnt from the experiments with casting inlays? Well, for the logos the process isn't as straightforward as it first seems. We'll get to the inlays separately, as the detail in those is its own challenge.

In the photos, it's pretty easy to see that the epoxy outside of the inlays has very little opacity from the pigment. There's a reason for this, and in a way I leveraged the way glow pigment crashes out of suspension in the epoxy to my advantage. I mixed up a 10g batch of the casting epoxy (J Dictum, but I think most casting resins have similar properties) with about 15-20% pigment. I heated it with a hair dryer to loosen the viscosity and allow major bubbles to rise out between mixing the epoxy and adding the pigment. I pretty much accept that bubbles in the pot are going to be a thing unless I get a vacuum pot, which I won't. The pour was done as soon as possible since pigment crashes quickly when the epoxy is warm and thin, giving it a stir during the process. The "Lumi" part of the logo was poured into the large open space, the U and the L. The thin epoxy flows out well into the narrower details, and I avoided dropping epoxy in a way that would trap air pockets. Flow is better as it migrates across the base. Having a lower fraction of pigment assists with the low viscosity as 30% gets a bit gritty and slightly thicker than is ideal. At this point, both logos were domed with epoxy without spilling over. The headstock was heated from underneath with a hair dryer, then the surface of the epoxy flamed to bring bubbles up and out which worked perfectly.

After this, I went back to the remaining resin to increase the fraction of pigment to a level that is too high for normal use. First, I mixed the existing epoxy in the pot, then poured out a gram or so into a second pot before adding more glow pigment. This would be in the order of maybe 40-50% which is where the epoxy gets very gritty and doesn't pour well. This was then heated to reduce the viscosity as much as possible, then drop filled drips of this heavy mixture over the logos. The idea is that the epoxy will flow into itself, and the pigment will crash through the whole lot to the bottom of the inlay pockets, which it did. And how. The pigment displaced the clear excess epoxy over the edges causing the spillover.

So the idea in principle is to wet the pocket with as thin an epoxy mix as you can. Being thin, it's easy to flame out the bubbles and get a clear pour. Being a super slow epoxy, it remains liquid enough that you can drop a heavily-doped epoxy over the top and rely on gravity to draw the pigment through and into the pockets. This wouldn't be easy or maybe even not possible to do just using a heavy mixture.

[Prostheta]

All in all, I thoroughly recommend Chaostrade.eu for sourcing glow pigments. Tom sent me a variety of samples in addition to what I ordered (including some wacky thermochromic pigment!), and the glow pigment is the best I've had since I started experimenting with these in the early 00's. For inlay casting and other small detail work around a guitar, I definitely think that M-ZZ620 is the best compromise between raw glow power and granularity. If green isn't your target, stick with the M grade of pigment grain (45-65μm) as this certainly is the most workable.

https://chaostrade.eu/en_US/c/Standard-luminescent-pigments/14

[Prostheta]

I do my best thinking when it's out loud (hey, you too right?) and here's the thing.

I've been going over in my head about how to make a neck carving jig, but mostly trying to resolve the issue of how I'd make one that works with necks that have radiused fingerboards. The options here are to radius and inlay the fingerboard off the neck, fit it and somehow make that work within a repeatable neck carving jig. The rotating sled will probably need a radius built into it, or perhaps bases that can be swapped out based on the radius of the neck seating within it. That sounds like a complication of a jig that needs precision, and compound problems are never the best to resolve as problems in one area often affect all.

The other option is to inlay and slot the board flat, surface the face flat after the inlays have cured, glue it to the neck, contour and then do a final radiusing on the CNC using some sort of workholding jig. This isn't easy either, as the neck will have few reference faces to work with. Radiusing by hand seems like a step backwards given my new direction of work approach....!