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Build progress for guitar amp/speaker cases

After purchasing a high-quality sheet of 3/4" thick walnut veneer plywood plus enough 4/4 rough walnut stock to create the edges, the first step is to lay out the cases to take advantage of the best grain pattern. Then the sheet is cut into manageable subsections.

layout 3 case side set for best figure

Layout 3 case side set for best figure

I'll rip-cut the case pieces in sets of two sub-pieces - either a top-side or bottom-side combination. I need to identify each sub-piece at all times so that later when they are all cut to size they can be reassembled into the cases.

top-side subsets with rough walnut for edging

Top-side sub-pieces with rough walnut for edging stacked behind

Using a combination of jointer and planer, I mill the rough walnut stock to over-sized edge material. The edge will be 3/4 inch wide so that a design detail can be routed in the top edge, and exactly the thickness of the veneer plywood. However, at this point I mill the edge material 1/4 inch thicker than the plywood prior to gluing. The edge material will be glued to the edge of the veneer with a spline hidden in the middle. This both strengthens the bond and aligns the edge material during gluing. I mill a quantity of spline - which is roughly 1/2" wide by 1/4" thick.  Pictured below is the process of cutting the groove in the edge material.  This is also known as cutting a dado in the material.

Milled Edge banding being grooved for spline

Milled Edge banding being grooved for spline

Similarly I cut a groove, or dado, in the edge of the plywood sub-pieces.

Cutting groove in plywood edges for spline

Cutting groove in plywood edges for spline

With all dados cut and plenty of spline material on hand, it's time to glue the edge material to the plywood. It is easiest to do this in sets of two sub-pieces being clamped together. All veneer faces need to be covered.  It is a tedious job but necessary to cover all of the veneer faces with paper taped exactly to the glue edge. You don't want to inadvertently smear glue on the veneer - it's a devilish job to get off without marring the veneer.

Glue edge banding to top-side subsheets

Glue edge banding to top-side subsheets

After removing the paper and cleaning the tape off the joints, now I need to remove the extra roughly 1/8" extra thickness of the edge material from all seams.

This is a critical step that requires great precision. Remember that the veneer show face is probably 1/45 of an inch thick - ie, paper thin. I don't ever want to cut into it, or there would be an ugly flaw.

So the steps I will take are first to use the table-saw with a guided-cut to remove the excess edge material to within 1/16 inch of the veneer, then use a pattern-bit on a router to remove the excess to within thousandths of the veneer, and finally hand-scraping to completely level the edge material to the surface of the veneer.

Cutting edge banding to close to veneer

Cutting edge banding to close to veneer

After running the long edge past a pattern-guided router, now I use a hand scraper to finish the smoothing of the edge material. A hand scraper is like a plane that can literally a 1/1000 of an inch of material at a time.

Using hand scraper to flatten edge banding exactly to veneer

Using hand scraper to flatten edge banding exactly to veneer

The result of all this post-glueup cutting, routing and handscraping is to make sure the edges of the pieces of the guitar case are exactly level with the veneer - without cutting into the veneer.

Close-up of edgebanding on veneer

Close-up of edgebanding on veneer

The next step is to cut the individual sides of the cases, each with a precise 45 degree angle.  To do this I use a large, very accurate cross-cut table that assures all sides are cut exactly.

Using cross-cut sled to cut individual pieces

Using cross-cut sled to cut individual pieces

Here are the three cases laid out end to end. Each has its long edges trimmed with 3/4 inch solid walnut.  The grain flows from side over the top and around.

Assembling case sides to show grain flow

Assembling case sides to show grain flow

To strengthen the corner joints,I insert 3 biscuits per joint. These stiff little biscuits swell in a joint upon application of glue and assure both the fit and tightness of the joint. To cut the slots for the biscuits, I use a biscuit cutter set at 45 degrees.

Cutting three slots for biscuits in each joint face

Cutting three slots for biscuits in each joint face

Now each case is test-fit without glue, ie, dry-fit.  This is time to make sure all slots have been properly cut, biscuits fit, and you have figured out how to clamp the joints tightly.  For the latter I make 4 temporary side pads with 45 degree clamping edges..

Dry-fitting the case joints

Dry-fitting the case joints

After making sure every case will clamp tightly, it's time to add some details of the design. First I route a design cove in the front of each case while it is a separate piece. Then I insert cleats into the sides. Again I use a spline glued within each cleat to secure it to the case wall. I route slots into the sides using a hand-router guided by a fence on the case side

Routing slots in sides for the splines that will hold the cleats

Routing slots in sides for the splines that will hold the cleats

It'a time for the BIG glue-up. After taping and papering every surface where glue might drip, I use the temporary pads plus clamps to close all four joints seamlessly

Final case glueup using temporary pads that direct clamping pressure directly through each glue joint

Final case glueup using temporary pads that direct clamping pressure through each glue joint

After removing clamps, paper, tape, glue, etc. I check to see that each case is accurately assembled.

Case after final glueup

Case after final glueup

Here is an example of the grain flow around a case corner.

Example of case grain flow around a corner

Example of case grain flow around a corner

With the cases complete it's time to make the additional parts - the speaker baffles and rear baffles. To make the speaker baffles, I first rough-cut the holes for the speakers using a jig saw.

Rough-cutting holes for speakers in baffles

Rough-cutting holes for speakers in soon-to-be-baffles

To cut the accurate speaker hole, I make a pattern that will guide a router to cut a clean, accurate circle. Later I will cover the plywood face of this hole with iron-on veneer tape.

Final-cutting speaker holes

Final-cutting speaker holes

After cutting the speaker baffles to size, and making the rear baffles, I lay out the placements of the screws holding them to the cases. Because the rear baffles must be removed from time-to-time it is best that their screws are secured with metal thread inserts. First I drill all holes for the baffles.

Drilling for screws and threaded inserts

Drilling for screws and threaded inserts

Then for the rear baffles I insert a metal threaded insert for each screw.  I use the drill press to ensure that the metal insert is installed accurately.

Using drill press to press in threaded insert

Using drill press to press in threaded insert

Now it is time to assemble the guitar amp cases. Here they are shown in various stages of final assembly. They are essentially done except for some additional hardware (handles, feet, chassis bolts)..

Guitar amp cases in near-final form

Guitar amp cases in near-final form

Chinese elm
Chinese elm