Saturday 13 September 2014

F style Eastman mandolin needs a new truss rod

The addition of a pin to secure the rod to the anchor was it's undoing. This is exactly where it broke. It's a compression style truss rod meaning it pulls against the back of the neck rather than up against a curved filet. The  fingerboard had to come off and a new truss rod needed to be made, the brass nut could be kept.
After careful removal of the fingerboard with heat and a palette knife. I used a chisel to remove the filet piece.
The truss rod broke at the very end where the pin had been installed. It's possible that the truss rod would have been better off without the pin, it was that little bit more that weakened the end. I understand the temptation to put it in. Peening the end doesn't seem like enough. However when you keep in mind that the real torque is in the tightening of the truss rod and that when loosened it shouldn't stress that connection nearly as much.
The bass I did recently came loose because the threading in the anchor stripped. In that case I recut the thread further up the rod and brazed it to the anchor. I'm happy with how that worked out. The bass has a curved filet truss rod and it's longer of course so it's a different situation.
I made a new 3/16" truss rod and 3/8" anchor and peened the end just like the traditional Gibson approach. I stuck with the compression style and put in a straight filet. With a mandolin neck being so short I think compression actually works better IMHO. However I also think it's a good idea to loosen the strings when adjusting a shorter neck. In some cases like when the action of the nut seems to tight, it's worth taking the time to clamp the neck straight and then adjust the truss rod.
 I cut the threads on the rod at both ends with a 10-32 die cutter,  and then fit the anchor to the short threaded end after sizing and tapping it to fit.
After rough cutting a piece of maple for the filet I used my belt sander with a thicknessing table to get it to final dimension. I glued it into place and let it dry over night before joining the fingerboard and the neck. The nut was used to index the neck to length, surgical tubing was used to clamp them together. I like that it wants to center the fingerboard on the neck. A couple of cam clamps held the end down. There was virtually no touch up involved when the clamps came off, just some glue to clean.
In the end it set up nicely and reminded me that I used to enjoy playing mandolin. I should get one or make one.

Wednesday 27 August 2014

Reinvented lap steel

This is a lap steel idea I've been working on for awhile. It was black and finished with oil. I sanded back and stained again with mahogany red. The plexi fingerboard is one idea black Corian is another. Purple heart treated with vinegar and steel wool to go black with contrasting fret inlays. I'm still thinking about it.

Monday 25 August 2014

Charango top repair

The Charango had an accident. The top was so badly damaged it could not be repaired. I started by removing what was left of the top. I knew I couldn't use the original as a pattern but I wanted it intact enough to match the original bracing. I found a similar piece of spruce among some off cuts. After thicknessing it I traced the body outline on the spruce and cut it close to shape except for the shoulder joint.

I used a compass to trace that shape onto the new piece, it was close and after some fine tuning it fit nicely. I had to come up with a different system for gluing the top on, spool clamps weren't going to work. After a bit of research I found a technique for gluing on lute tops. It worked well and there just some refinishing to do. I decided French polishing was the best choice and I'm happy with how it turned out.

Wednesday 6 August 2014

Martin 000 my pickguard is shrinking

Shrunken pick guard syndrome, several manufacturers glued pickguards directly onto the wood. The pickguard would shrink and crack the top. Here's one being repaired. The guard has been removed and the cracks are being glued up supported on the bottom with small spruce cleats. I like to make mine round, it allows me to use a plug cutter and then I can thin them down to whatever thickness I want. In this case I shaped them to fit around the braces.

Wednesday 30 July 2014

Saddle slot routing jig

For years my saddle routing jig consisted of a piece of plywood with a hole in it and various pieces of taped down strips of this and that. The whole tedious and messy looking thing would corral the router into making a perfectly straight cut. Over the years I've had four pieces of plywood with a hole in it and somehow lost every one. I guess it doesn't look like anything, so it gets lost or put in unlikely places.
I spent to much time looking for the last one and decided it was time to make one I wouldn't lose. 

A top piece designed to use with a template guide was made and considered. The idea was that the slot for the guide was small enough the placement could eyeballed very close to the correct position and then fine tuned. In practice it was to hard to see where the bit was.

A larger opening to fit the whole base was a better idea. It meant that the base didn't need to be fine tuned to the template guide and there's lots of room to see what's going on. I'm still scheming on a light that will go around collet assembly, I'm pretty sure I saw something like this for screwdrivers. Initially I used a couple of scraps with two sided tape to set the length of cut.  The final design includes the knurled brass nuts with the aluminum slider.

End of story, it works really well, took a couple of hours to build and I probably won't lose this one. One other thing, it sets up a lot faster.

Thursday 24 July 2014

Loose machine head covers

Kluson style tuners with cast back covers sometimes come loose from the base. I've seen them installed on Gibsons and Martins among others. The back cover is peened onto the base, meaning there are posts that go through a hole and then they are punched or hammered in a way that makes the post mushroom and that holds it in place. Over time they can loosen and sometimes fall apart. I use a spring loaded center punch and a small anvil to repair this problem.

Tuesday 29 April 2014

Shop made control knobs

To be installed: A forty year old Dearmond acoustic pickup system complete with wiring harness. 1 meg volume pot 250k tone pot I did not make a note of capacitor value.
While the pickup was sealed I'm pretty sure it's a piezo. I replaced the jack with an endpin model. Each knob required six different drill press operations, a forstner bit for the recess that covers the nut and washer, a brad point for the shaft and a plug cutter to shape the knob.
A brass insert is glued in place and threaded through the side to fit a small allen screw. This allows a small metal rod to be temporarily mounted, the while assembly is chucked in the drill press for sanding, polishing and finishing. The drill press is used again for the V and T impression which is filled with a putty pencil, polished again and installed.

Thursday 17 April 2014

Tak dot on

My customer likes the guitar but misses the fingerboard position markers. This is a job that's a bit more of a challenge with frets in. Once the layout work was done it was time to drill the holes.  To make it easier I used a drill bit  depth collar and set the depth really close to the exact thickness of the dots. After that a file did a good job of making the dot markers flush.