Archive for the 'tools and jigs' Category

Whiplash!

Wednesday, October 15th, 2008

Here’s a classic example of why I go to so much trouble to construct a scarfed, back strapped headstock. The owner of this Gibson Les Paul Standard wasn’t aware of having broken the neck - he opened the case and found it broken. Most likely, the case tipped or fell a short distance, and was stopped abruptly by hitting something. The weight of the tuners, supported at the end of the neck, combined with the Gibson Les Paul’s 1 piece neck (which results in very unfavourable grain orientation in the headstock area) and large trussrod adjustment cavity, allowed the whiplash effect to crack the headstock cleanly away from the neck.

From the side you can see that the only thing holding this all together is the plastic headplate, which is flexible enough to act like a hinge:

A (badly focused!) close up shows how little wood is left in the neck once the trussrod cavity is cut - you can see righ through the headstock!

The good news is; as easy as these breaks are to produce, they’re also pretty easy to fix. The headplate holds everything in alignment, and there is plenty of surface area for a good glue joint, which will be as strong as the headstock was originally.

To clamp the break closed, I use a spanish windlass setup. I run a piece of electrical cable (strong, with a cushioned surface, but not very stretchy) through the tuner holes in the head and around the lower strap button, then add tension by twisting a piece of scrap timber in the loop. Once it’s tight, I extend the scrap out to one side, where the neck prevents it untwisting.

This setup only works if the head veneer is intact, but is a very easy way of closing up the fine feather-edge of the break. It also allows easy access to all sides of the repair to clean up glue squeeze out. With the squeeze out wiped away with a damp cloth, I add an f-clamp (with a flat clamping caul and leather pad) to apply extra pressure of the rest of the break.

After for 24 hours, I unclamp the break, and carefully level the repair. Very little levelling is required, and the result afterwards is pretty clean.

However, it can be improved. Gibson still use nitro lacquer on their guitars, so this is what I use for touch up. I apply generous drops of laquer with the tip of a brush to fill any missing chips of finish, then sparingly brush over the entire area.

This lacquer needs time to cure, at least 1 week, or prefferably longer. Once it’s dry, it’s relevelled, wet sanded to 1200 grit and buffed to a shine.

Not a bad result if I do say so myself!

P.S: The guitar didn’t actually keep changing colour - that’s my photography and image editting!

Simplifying scarf joints…

Monday, September 4th, 2006

I’ve been scarfing my headstocks as long as I’ve been making guitars, because it’s a stronger and less wastefull than sawing out a 1 piece neck. Because both of the parts being glued in a scarf joint are wedge-shaped, getting the joint glued and clamped can be a bit like wrestling a buttered ferret. There are many ways round this, from pinning the joint in areas which will be cut away, putting some nipped of staples on one of the glueing faces, or making an elaborate clamping jig to hold both pieces. Here’s my solution, which I think is pretty much foolproof (to this fool at least…).

With the pieces cut and planed, I first check fit and alignment:

scarf01.jpg scarf02.jpg

Then, with the pieces arranged properly, I tape one side of the joint with common or garden masking tape, so that joint can be hinged open:

scarf03.jpg scarf04.jpg

I hinge it completely open to expose the glueing faces, apply a generous amount of titebond original, and spread it out:

scarf05.jpg scarf06.jpg
scarf07.jpg scarf08.jpg

Then, I close it and clamp it. 2 small g-cramps apply most of the pressure, and 4 spring clamps hold down the feather edges at each end of the joint.

scarf09.jpg scarf10.jpg

As well as clamping the joint closed, the clamps push down on the masking tape, and prevent it lifting or slipping, which in turn keeps the joint perfectly aligned as you apply the clamps - simple, but it works really well.

The result:

scarf11.jpg scarf12.jpg

Coming soon: Back strapping the headstock.

Sawdust generator

Tuesday, August 22nd, 2006

I’ve had a few requests to post details of the top carving jig which shows up in some of the progress pics of John’s guitar. It’s a simple project to knock together, and makes roughing out a carved top much faster. It’s also an impressively efficient way off spreading wood chips over a large area…

One of the common techniques for roughing out carved top instruments is using routers to cut a ’step’ pattern into the wood. This technique works well, but is pretty nerve wracking (it’s very easy for the router to tip and cut deeper than you want) so I settled on this solution. The pictures should be pretty self explainitary, but questions and suggestions for improvement are welcomed.

Here a shot of the jig with a roughed out top. This was my first test, so the contours are not at final dimension yet - the edges were later thinned down to .25 inch.

carve_with_jig.jpg

The router is suspended about a little over 2.5 inches above a flat workboard, enough height to carve a top glued onto a body for a Les Paul style instrument. The router is attached to the base with 2 M6 machine screws.

At the moment the jig is attached to the workboard with 2 clamps, and is perfectly stable and solid, but ultimately it will be screwed in place. However it’s done, you must be completely condfident it can’t move *at all* - You really don’t want it getting lose and coming to find your fingers…

jig.jpg

The guitar body registers off a wooden guide which runs in the body of the jig. The radius at the end of the guide matches the radius of the cutter in the router; a 1″ dish cutter bit.

This image shows the guide removed from the jig.

jig_with_bearing.jpg

This shows the cutter and guide. The guide is adjusted by sliding and clamping with an F-clamp. In time I’ll add thumbscrews and an adjustment slot to the guide piece.

cutterjpg.jpg

Here’s the body registering off the guide. The depth of cut is adjusted with the router plunge mechanism and depth stop.

With the cutter speed up high, and taking no more than 2mm with each pass there is no tendency for chatter or grabbing, which I think is helped by the rounded edges of the bowl cutter. The steps end up very smooth, though care has to be taken to keep the edge of the body square to the jig, otherwise the width of the rebate created can vary.

The jig is also great for routing binding with a bearing bit.

cutter_with_body.jpg

You can space your contour lines equally, which will create an even stepped surface, but I drew out the curve I wanted to create, and then mapped the steps required to come close to this shape if I removed 2mm each time.

Then, I transferred these measurements to the guide - I line up each mark with the edge of the jig, and drop the cutter 2mm each time.

contour_map.jpg

Here’s the result - hopefully a few minutes with a small carving plane and a spokeshave will get me very close to my final shape. In this shot I’ve planed the neck angle into the top with a jack plane - the jig doesn’t do that bit for you :(

26_roughingout_top.jpg

Potatoes RAWK!

Tuesday, April 18th, 2006

Well, they do.

Installing the tremolo was all new to me, and required at least one specialised tool I didn’t have - a superlong drill bit. I checked a few of my normal tool suppliers, but nobody had anything really long in the right size, so it was time to improvise.

Funnily enough, Easter Sunday at my grandparents yielded a perfect solution. Dad was browsing a 1948 signed edition of ‘The Amateur’s Lathe’ by L.H.Sparey (I know, how rock and roll is that?), which contained a paragraph on making extension drills, by turning down the drill shank, boring a suitably sized hole is a piece of steel rod, and brazing the drill into the hollow centre of the rod. Most importantly:

To prevent the brazing heat from softening the drill it is an old dodge to insert it into a potato during the brazing operation.

-The amateur’s lathe p.85

Duly equipped with a small metal working lathe, and a carefully calibrated potato, we made up a special drill for installing tremolo claw screws. Result!

The 4mm mild steel was originally intended to become a Gibson style compression rod and is pretty soft, but this makes it very easy to use, since it can be flexed slightly to get the best angle into the tremolo cavity. On a similar note, the only way I could get at the screws to adjust them was to daisy chain 3 magnetic screwdriver bits to make a long bendy screwdriver - not elegant, but it works!

With the trem springs in, it was time to string it up. Lots of fiddling to do to get the optimum setup, but even with an unfinished nut, and the neck relief unset, it plays nicely, with no buzzes and very low action. Apart from final levelling and buffing of the lacquer on the headstock and trem cover, all the finishing is complete - leaving the wiring and final setup still to do.

The spiffy case was John’s birthday present from Pete and Sarah. I was really hopefull they’d be able to deliver it to him with the guitar inside, but the finishing trouble I had delayed me too much. It’s a Hiscox case, and I can see why they have a good repuatation - it’s well put together, very sturdy, and (IMO very importantly) not too heavy.

There’s good news, and there’s bad news….

Wednesday, April 5th, 2006

Well, it’s been a while since the last update, and lots has happened in the intervening period. First thing (and the reason for the good news/bad news tagline) was the body binding:

The good news: I finally got the hang of bending wooden binding around a tight radius:

The bad news: I only got the hang after breaking all but 3 of my binding strips, for a guitar which needs 4 binding strips….*sigh*

Anyhow, this required a change of plan, since I had no more pau ferro for binding, so after experimenting with different combinations I settled on wenge binding with a curly maple and pau ferro veneer purfling. I laminated the binding out of .7mm veneer, which made the tight curve at the tip of each horn easier, but meant I had to ditch the flame maple side purfling on the body. It also meant re-binding the neck in wenge to match, but it was worth it to get a consistant theme throughout the guitar, and actually works better than the original plan, since it contrasts better by on the darker areas of mahogany endgrain.

That little saga took quite a while, but was eventually scraped flush and sanded smooth. After completing the binding, I had to build a router base for my dremel tool to do the inlays on the neck:

It got it’s first outing when I used it to inlay a pau ferro/curly maple/wenge accent strip in the back of the guitar, and across the tremolo spring cover:

After all that fussy detail work, it was time to grainfill and sand the body in preparation for spraying, which was delayed for a couple of days by the death of our air compressor. Fortunately, I had access to Dad’s impressive diagnostic abilties, which (coupled with a comprehensive dismantling and a brief trawl of the web) revealed the problem was a blown capacitor - £3.49 and 15 minutes of tinkering had it running again - thanks Dad! The forced interruption gave me a good chance to de-dustify the garge and thoroughly clean my little spraygun, which resulted in a nice smooth application of the lacquer (marred only by some wierd blistering in places which needed cutting back and respraying).

With the finish curing I worked on my inlay design, a variation on the Martin split diamonds and snowflakes pattern. I cut it out of paper to see how it looked, and so I could run it by John for approval. Then, with the OK from John, I cut the pieces from Mother Of Pearl (MOP). I cheated a bit and used a cut off wheel rather than a jewlers handsaw since the pieces were fairly geometric in shape. Mouting the cutoff wheel in the benchtop milling machine made it easy to keep the sizes and shapes consistent and accurate.

With all the pieces cut, I tacked them to the neck with small spots of superglue, and scribed around them. I routed the cavities with the dremel and a variety of small dental bits, then glued in the inlays with epoxy mixed with rosewood dust - pics tomorrow when it’s levelled and polished up.

Glue up…

Tuesday, February 7th, 2006

The tops have been glued on, and the cavities completed. John’s guitar has only been temporarily glued, with a bead around the edges of the top. There is a method in this madness; I plan to carve the top in situ, then separate it with a hot spatula, and hollow the inside some more, before regluing the top. I had planned to carve it before glueing in place, but the blank had cupped a little since glue up, so I had to find a way to stabilise it whilst carving - time will tell how much of a PITA I’ve made for myself :) It’s more work, but paired with the body chambering it should make the guitar livelier and more acoustic sounding, something John liked in the maple DC which this guitar is based on.


Today I planned to start top-carving, but progress has temporarily been interupted by the addition of a new bench to the workshop. It’s a traditional solid beech workbench fitted with 2 Record no.52 vices, and was a steal at £25 from my old university. I also got a retired bobbin sander which will be a great addition to my stationary powertools - another great deal for £60, including a few spare sanding sleeves and 3 different bobbin sizes. It’s a Secret & Marriott ‘Mini-bob’, made in Burton on Trent. If anyone reading this knows anything about the company I’d love to hear some background. They still exist, but as an an egineering works, not a tool manufacturer.

Excuse the state of the garage - everything is in chaos to make space for the new bench. Hopefully I’ll get a good ‘after’ pick to show the bench once it’s been properly cleaned up.

Some progress…

Thursday, December 15th, 2005

…and a new toy.

I got some necks roughed out today, from some mahogany which I had left over after building my Les Paul. I originally thought I’d get a 2 piece flatsawn neck out of this piece, but with a little careful cutting I squeezed two quartered necks out:

One will go in my stock pile for later, the other got a wenge centre lamination, and will be the neck for a new doublecut. Like Simo’s neck, I tapered the centre lamination, from 11mm at the heel, down to 8 at the nut. With the quartered mahogany, and a centre laminate of super-stiff, quartersawn wenge, this’ll be a nice stiff neck.

Also, this evening I went to my Grandparents for supper, and my Bon Papa presented me with a lovely 1930’s Record #5 in very nice condition, complete with honing guide in original box. It’s a great present, and will get a lot of use - thanks Bonnepapa.

All I want for Christmas…

Thursday, December 8th, 2005

…is a 17″ bandsaw.

And somewhere to put it.

Sadly, I doubt even Santa could hande the logistics of fitting a bandsaw down my chimney, so I’ll just have to make do with the cheap & not remotely cheerful alternative:

Don\'t try this at home...

This is definately not the way to resaw maple :(