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beltjones

First Build, so many lessons learned

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Ok, I need to make templates for control cavities and the recessed cavity covers, but I'm struggling with making them look good. I'm about to scour all yall's threads for ideas.

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There's a number of ways as you'd expect. I have a lot of approaches I've used, but these days I tend to get them laser cut to make them as complex or custom as I want.

Are you more concerned about achieving the shapes, or corresponding positive/negative templates with a degree of offset for the cover to fit in?

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I'm really just trying to make something that doesn't look amateurish. I don't want to route some wonky looking cavity, that's pretty much it. Using half-round files and trying to carve attractive circular shapes in MDF isn't working for me.

Previously I was carefully drawing out cavities with a compass, protractor, and straight edges, then transferring the drawing to MDF and trying to cut out the pattern. Today I tried a different tactic - it occurred to me that I have hole saws, I have everything I need to lay out the shape I want. So I simply drilled three 1.5" holes and used a saw and a rasp to connect them with straight lines. I may take one more run at it, but I think my control cavity is pretty much good. 

Top is the one I did strictly with hand tools, the bottom is the one I did with the hole saws. 

YHjHYkc.jpg

 

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I think it was @psikoT who used to use short offcuts of MDF to make little 'fences' that he'd use as templates to build up the master template. When you think about what you're trying to create with the single coil pickup route just about every edge is a straight line.

If you use a pattern router bit that has the same diameter as the two ends of the pickup cavity (eg, a 3/4" dia one would probably do it), you only need five straight edges to create that template of yours - one for the long edge, two for the diagonals and two little stubby ones to limit the left and right edges. Some MDF offcuts and a few strips of double sided tape and you'd have a better looking template than you could hope to achieve freehand using hand tools only.

A humbucker cavity is nothing more than a few rectangles.

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Ok, I gotta be honest. I just ordered a plexi pickup routing template. 

One thing that I'm struggling with now is how well mated the top needs to be to the body prior to gluing. I have planed the body flat, and I have planed the glue side of the top flat, but when I put them together they're not exactly perfect. 

It occurs to me that with a straight edge you can only test for flatness in one dimension - along a straight line. So even if I lay a straight edge across both surfaces in multiple orientations there are still some peaks and valleys that exist on each piece of wood, and when I put them together the result is an imperfect joint. I can put the pieces together and close up the joint with my hands, but I have pretty strong hands. 

I suppose that without specialized tools (CNC, for example) it may be impossible to get each piece absolutely perfect, and I'm trying to decide how much time to spend chasing perfection. I may spend one more day on it before proceeding with everything else.

Edited by beltjones

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Damn, again I waited until I was home from work before I could pick up on this one.

8 hours ago, curtisa said:

I think it was @psikoT who used to use short offcuts of MDF to make little 'fences' that he'd use as templates to build up the master template. When you think about what you're trying to create with the single coil pickup route just about every edge is a straight line.

If you use a pattern router bit that has the same diameter as the two ends of the pickup cavity (eg, a 3/4" dia one would probably do it), you only need five straight edges to create that template of yours - one for the long edge, two for the diagonals and two little stubby ones to limit the left and right edges. Some MDF offcuts and a few strips of double sided tape and you'd have a better looking template than you could hope to achieve freehand using hand tools only.

A humbucker cavity is nothing more than a few rectangles.

 

This this this. All over. I made a custom template for a custom single-coil bass pickup this way. I drew it out (also on MDF) including the corner radii, used Forstner bits (is this what you mean by "hole saw", @beltjones?) to define the larger circles and the natural tendency for router bearings to leave matching internal radii within a set of temporary scrap fences.

I spent twenty minutes hunting through the graveyard that is Photobucket, and couldn't find a photo of this process. The most I could find is the result.

IMG_6102_zps65bf665c.jpg

 

CAD plan (or hand-drawn). Orange outline is the lightly-relieved pickup cavity.

1.jpg

 

Layout, arrangement of temporary fences and routing paths. Even drilled the smaller inner radii but this wasn't necessary.

2.jpg

 

 

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I might have that template around here somewhere....

1 hour ago, beltjones said:

Ok, I gotta be honest. I just ordered a plexi pickup routing template. 

 

That works too. :lol:
Just do yourself a favour and copy it into plywood rather than relying on acrylic to be durable enough. It isn't. Or at least, "it is until it isn't....."!

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1 hour ago, beltjones said:

Ok, I gotta be honest. I just ordered a plexi pickup routing template. 

One thing that I'm struggling with now is how well mated the top needs to be to the body prior to gluing. I have planed the body flat, and I have planed the glue side of the top flat, but when I put them together they're not exactly perfect. 

It occurs to me that with a straight edge you can only test for flatness in one dimension - along a straight line. So even if I lay a straight edge across both surfaces in multiple orientations there are still some peaks and valleys that exist on each piece of wood, and when I put them together the result is an imperfect joint. I can put the pieces together and close up the joint with my hands, but I have pretty strong hands. 

I suppose that without specialized tools (CNC, for example) it may be impossible to get each piece absolutely perfect, and I'm trying to decide how much time to spend chasing perfection. I may spend one more day on it before proceeding with everything else.

I'm sure that there are better ways, but one method I've used in the past that helped - once I was pretty close to flatness - was to use school chalk on a 1' square piece of 1/4" ply, liberally applied, and then rub the coated ply over the mating surface.  Any high spots will show as the chalk will be rubbed off onto them. 

Then I use a cabinet scraper to scrape away the high spot and repeat until the whole surface has chalk transferred onto it.  Then do the same on the other mating surface 

It won't sort two mating surfaces that are way out, but it is a decent method for sorting out pesky high-spots.

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Another way is to make a sanding table. Glue (spray adhesive is great for this) 4 or 6 full sheets of 80 grit to a flat surface sand the entire gluing surface of your parts at the same time. Draw pencil lines all  across the surface of the piece to be sanded, and then sand till all the line disappear.

SR

 

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These are great ideas. Thanks guys! I'm going to spend at least another day (not full day, I mean the 20-30 minutes at a time, here and there, that I have to work on this) flattening both pieces to improve the joint.

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+1 for the sanding table

It just takes time and patience. Scribble all over your surface and sand away until it's all gone, as @ScottR says

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My take on the sanding table is to find a business that has a drum sander. One of the large format machines. When any of these get a nick or tear in the belt, the whole thing needs to be changed. Cutting across the belt through a fault yields an enormous sheet.

These: https://www.abrasives-online.co.uk/index.php?main_page=index&cPath=58

They're normally in packs of ten and cost about €12-20 dependent on size. Most will yield a sheet the size of a table top. If you ask nicely, you might be able to buy a single new belt. :thumb:

I used the last one we made to true up the glueing faces of necks before putting on the fretboard, cleaning scarf joint glue faces, etc. Really useful, and lasts forever.

BTW. I think "Jepuflex" is named after the place up north where they manufacture these sheet abrasives, Jepua. Once PG's Patreon support has reached a certain point, I'll see if I can do a day up there. Grilling Mirka for their product knowledge should be useful.

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3 hours ago, Norris said:

+1 for the sanding table

It just takes time and patience. Scribble all over your surface and sand away until it's all gone, as @ScottR says

Time and patience you say... 

I spent about 40 minutes with my new sanding table that I threw together and it's much better, but not perfect. I think another 30 minutes or so and we'll be there.

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9 hours ago, beltjones said:

Time and patience you say... 

I spent about 40 minutes with my new sanding table that I threw together and it's much better, but not perfect. I think another 30 minutes or so and we'll be there.

I tried to like your post, but apparently I've used up all my reactions for today! :D

Once the pencil marks are sanded away it will be flat (assuming your sanding table is flat to start with!)

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If it isn't, the general high/low spots will be evened out over a large area. A trick with thin boards is to put some marigolds on for traction and ensure that the board is pressed down evenly, but not too hard. Your hands tend to deform a board leaving rounded edges or one thinner side if you go at it hell for leather.

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Ok, I almost didn't post this because it's embarrassing. I spent a good amount of time yesterday with the sanding table flattening both the wenge top and the body. I got both very close, and decided I would come back to it today with fresh eyes and finish up.

So after about another 30 minutes with the sanding table I figured it was done. I put the pieces together and they fit very nicely, with just about a .25mm gap in places that I could close with finger pressure. I needed to run an errand, so I packed my son into the car and left for about three hours, leaving the guitar in the garage. 

Well, the wenge moved on me. I feel like I'm back where I started. I know the surface doesn't have little peaks and valleys, it just bowed about 1mm on the far edges. I think at this point I'm just going to say screw it and proceed and not leave the wenge in the garage again for any length of time.

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It'll be fine. Glued to the body core, that slight cup won't be enough to pull the entire body out of whack. Movement happens.

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8 hours ago, Prostheta said:

Movement happens.

All the time....whether you see it or not. It's one of the joys of wood working. AS @Prostheta says, that is not enough to hurt anything, so glue it up and go on to the next step.:thumb:

SR

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Moisture. I have had so much direct experience with taking in wood and drying it at work that I really should relate this.

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As much as I may curse wenge for being difficult to work with, for splintering, for moving, etc, I think it just saved my project. I was routing the top to match the body, and the router bearing slipped and the bit dug into the neck/body transition area. Luckily this wenge is like routing steel, so I was able to feel the slip and the wenge protected the padauk from too much damage. If I had been using a maple top this guitar would be in the garbage can right now. 

Here's where it dug in a tiny amount before I stopped it.


XtqumHS.jpg

And here's the repair. Not bad - I'll keep perfecting that transition once the top is glued on.
b4WzYip.jpg

Edited by beltjones

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38 minutes ago, Prostheta said:

Ah, jeez Rick. I think this is minor.

Or in my case, 'Ah jeez Rick.  If I produced this cut, I'd be patting myself on the back for doing a great job.'

Great job, Rick. :)

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7 hours ago, Prostheta said:

Ah, jeez Rick. I think this is minor.

Thanks man. My pictures are pretty terrible, but when the slip happened there was nothing preventing the router bit from cutting directly across the neck. Nothing, that is, but a rock-hard wenge top that it had to cut through first.

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I started carving the top, beginning with the front part near the fretboard. If I carve this part before the top is glued on I won't have to worry about slipping and jacking up the neck. 

ecBszc4.jpg
uYb1AUr.jpg
FrXT7V9.jpg
On that lower horn I'm more or less happy with the carve. I think it will look cool once I carve the other edges, though I may make it more severe with more of a peak in the center. On the upper horn I'm thinking there is too much flat area just past the carve. I think I may attack it with a grinder with a sanding disk to round it out quite a bit more.

LfGly2G.jpg
 

On the plus side a Christmas Miracle has occurred. Remember how I said I spent all that time flattening the top and body, only to have the wenge bow on me? It went back to normal, and now the top and the body fit together perfectly.

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It must have been that afternoon you left the wood sit in the wrong place. I've had blanks do that to me when I prep them at work or at the local community college, then put them on the back seat of the car on a wet day or midwinter. Once in the home shop, they go back to normal.

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