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Reshaping Pickup Cavities


FrankW86
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Hello everyone. I've been lurking around here for a while, ever since I decided to refinish my RG.

I won't bore you with the context for now but go straight into my issue. I'm converting from ring mounted humbuckers to direct mounted, using John Wallace's threaded insert method. I already partially filled the cavity. It's level and ready to accept the new pups. These Dimarzio's are quite a bit smaller than the cavity. This looks horrible. How to fill up/reshape them?

My idea is to use epoxy putty to plaster the sides. Then us my Proxxon (think high-quality Dremel) to grind and sand things back into shape. The putty is originally used to patch small holes or cracks in boat hulls. It's flexible but hard enough to drill in. I don't own a proper router so this seems the most practical solution in my case.

Do you agree? Or do you suggest a different method?  

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What about direct-mounting the pickups but leaving the rings in place? The rings would then only be for looks but you'd save yourself a lot of work, give yourself the option of reverting back to the original pickup mounting method and allow for future replacement of the pickups if you wanted to.

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On 2/20/2019 at 9:43 PM, ScottR said:

If you are planning on painting the body, that could work. If you are planning a finish that allows the wood to show through, the putty will probably be as noticeable as the gap.

SR

 

Yes, the body will be painted a solid color. The epoxy is designed to be painted over, so I'm not too worried about that.

On 2/20/2019 at 9:41 PM, curtisa said:

What about direct-mounting the pickups but leaving the rings in place? The rings would then only be for looks but you'd save yourself a lot of work, give yourself the option of reverting back to the original pickup mounting method and allow for future replacement of the pickups if you wanted to.

One of the reasons for ditching the rings is the look. RGs need either direct mounted pickups or a pickguard to look right for me. If push comes to shove the rings can always come back on to cover up any carnage I inflict. 

But other then time and effort, my proposed method should work? I know the epoxy is drillable. Maybe I should test how it reacts to the different bits.   

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I come from a long line of "if it's worth doing... it's worth overdoing".  look on craigslist for a router you can find one for $25 easily.  my vote would be to make templates, cut out a square, fill that square with wood, then rout the pickup proper.

Epoxy is great stuff and will work for sure... just not fun to sand.  I filled a guitar that had been shot 3x... had to sand down the overfill and it was difficult because the wood around it would sand sooo much easier - and it was maple!  so my advice would be - if you are going to do it - be careful to not overfill.  I would use cardboard/tape to make a 'barrier' that you could fill and hopefully be close to done.

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42 minutes ago, mistermikev said:

I come from a long line of "if it's worth doing... it's worth overdoing".  look on craigslist for a router you can find one for $25 easily.  my vote would be to make templates, cut out a square, fill that square with wood, then rout the pickup proper.

 

  I'm aware that this is the proper way of doing it. But you don't know the Dutch secondhand market. Nothing within driving distance. Nationwide the cheapest is a 3 yr old DeWalt which is €30 below retail price. What can I say, it's a Dutch thing :)

1 hour ago, mistermikev said:

so my advice would be - if you are going to do it - be careful to not overfill.  I would use cardboard/tape to make a 'barrier' that you could fill and hopefully be close to done.

 

 My epoxy has a Play-Doh/putty consistency. I'll smear a layer on one side of the cavity. Then press a mold/template of the correct shape against it to give me a rough shape. Any excess can be scraped off. After hardening, I'll use my Proxxon rotary tool to route, grind or sand it down. 

I already have a little test setup hardening. Will check next week how the epoxy reacts to the reshaping. 

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3 hours ago, mistermikev said:

I come from a long line of "if it's worth doing... it's worth overdoing". My vote would be to make templates, cut out a square, fill that square with wood, then rout the pickup proper.

Or worth doing right, Either way I agree, this would be the proper way. Maybe you could borrow a router? Even if you fill with epoxy a router and a good pickup template its going to be the correct tool to square this up properly. 

Some thoughts, Filling cavities in wood is challenging because the filler piece and the piece being filled almost always shrink and expand at slightly different rates over time. This happens even when using the same species of wood with the same grain orientation. The end result is almost always a visible line in your finish where the filler edge is. If you're using a resin, epoxy, solar-res etc. the effect is magnified. 

Is your current pickup route really that bad that its not suitable for a direct mount? Ibanez usually has pretty decent cavities. Have you considered a trembucker? Post a picture maybe?

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Here is quick picture. You'll have to excuse the quality. I somehow managed to get sand between the lens and glass. The second pic is what inspired me to try this.

As you can see, I not talking huge swathes of epoxy. Maybe 2 to 2,5mm at it's thickest in the 'ears' (don't know the correct English term). Let's say I apply 3mm on the sides, 1mm across the length. Surely a rotary tool with proper router bits and plunge attachement can handle that? 

IMG_20190222_234202_2CS.jpg

Elite-Full-Hardware-Shot.jpg

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I suspect your method may work, but I'd personally want to experiment with it first over an extended period of time.

Three issues I can see with your method:

  1. My experience with thick layers of epoxy (>5mm) is that it tends to not fully cure in the middle while the outermost layers set hard, retaining a slight rubbery/waxy consistency when cut. Some epoxies may work better than others. Even the mixing ratios between catalyst and resin may be critical.
  2. Given time, humidity and temperature changes the epoxy and wood will likely shrink and expand at different rates, which could result in the bond between epoxy and wood weakening. This could be as minor as hairline cracking underneath the finish or as major as whole chunks peeling away. This would probably be the main reason why filling a pickup cavity with an oversize piece of wood and routing it back down to the correct shape would be better, as the difference in rates at which two relatively large pieces of timber expand and contract would be less than two completely dissimilar materials sharing a comparatively small surface area.
  3. If you are going to use a plunge attachment on the rotary tool then set yourself up some square, straight edges on the body to help guide the perimeter of the plunge base in straight lines and create square corners. Practice first. Any slight deviation in the reshaped edges if going freehand will tend to show up more clearly when the square edges of the pickup are positioned alongside them, and might end up looking worse than the original un-modified cavities.
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