Tapping an internal M4 thread in an M6 brass threaded rod,

Well, by hanging the strap between the nut and the end block the player is putting a side strain on the neck and the place where this will fail will be at the body/neck join. By having the strap between the bottom of the neck (the heel) and the end block all the strain is taken by the body which is a nice strong box construction. Whatever the type of neck/body joint is used (and there are dozens of designs) there should be plenty of meat to screw a strap button into.

Murrmac, any chance of a picture of your guitar?

cheers,

Rod

I'm gonna chip in here as an amateur luthier.

drilling the heel of the neck should not cause you any issues, I could better advise on this if you could supply a dimensioned drawing of the heel, but mahogany, being very close grained hardwood will not take harm from some intrusion.

You really need to knurl or similar on the outside of the insert to give the adhesive a good bonding surface.

What type of neck joint construction has been used, is the heel dovetailed into the block or, as Taylor guitars sometimes use, is the neck bolted into the body block?

Graeme

Edited By CoalBurner on 21/12/2013 15:14:05

Hi Murrmac,

Just had a look at a couple of my guitars for ideas. They pretty much use the standard strap button or nothing at all, requires a lace or something attached to the neck.

I think adding a 'Z' shape bar (basically a lever) might introduce radial and lateral forces on the mounting and over time it could loosen and fall out.

Have you considered a harness as an alternative to a strap.?

**LINK** ...a bit pricy though (IMHO).

cheers all ...just got in and am just going back out ...will take everything on board and will post tomorrow.

Murrmac,

There are ready made M3 inserts that are within your size range and designed for both plastic or wood applications

**LINK**

They also offer M4 threaded inserts complete with a hex socket drive to help with insertion if you can accomodate the larger diameter

**LINK**

there is an online shop and you can get small quantities.
I have no connection with them but have used similar parts in the past to good effect.

Bob D

Just got back in and am now heading off to bed, but you can see pictures of the guitar here **LINK** . Mine is the Cuban Mahogany guitar listed as "out of stock".

The neck joint is a dovetail, so no worry about encountering bolts, and the 2 1/4" length brass rod will stop short of the truss rod by at least 1/4" .

The brass inserts linked to by Bob D are very useful in their place, but unfortunately they are way too short for my purpose. As Ed pointed out above, the Z bar is in fact acting as a lever, and to counteract this leverage the rod does really need to go in at least 2"... a 8mm long brass insert wouldn't do the job, because all the force would be concentrated right at the very end of the heel, where the wood is thinnest, and there would be a serious danger of the wood splitting eventually. The M4 bolt however doesn't need to go in any further than 15mm.

I have decided that the solid rod is the way to go, grooved in the lathe as suggested above, and bedded in with epoxy. The end of the brass rod will sit just underneath the surface of the ebony end cap, and I will also machine a 6mm OD brass spacer about 3mm long to act as a washer so that the stainless steel flat bar doesn't come into contact with the end cap when it is installed.

a most interesting thread with some wonderful engineering solutions and ingenuity!

i dont play the guitar, and my eldest daughter who does (professionally), doesnt use a strap. i play the ukulele banjo (george formby style), and the thought of using a strap is anathema to players of same. it is very difficult to hold same when standing up, but that's the way it's done. the thought of drilling the neck heel on some of my very expensive ukulele banjos just isnt worth considering, even though playing of same would be far more comfortable and easier.

ive done all sorts of other jobs on same in the workshop including re-fretting, and fitting planet tuners. i notice that with a quality instrument the neck resonates and you can feel same. anything that might affect same ie drilling it might be detrimental as well as affecting the potential re-sale value of same.

i think there is something to be said for learning how to hold the instrument and putting up with the lack of a strap. a completely non-engineering solution im afraid!

cheers,

julian

I don't think I would be wanting to bore holes into a musical instrument of any significant value, but I have fitted metal bushes into wood a few times while building my steam boat. You don't need a screw thread on the outside of the bush, if you just provide some shallow grooves and epoxy it into place it will hold against any likely force. (The knurling mentioned earlier would be good too, except I see you haven't got a knurling tool.) The hole can be just a good clearance fit. This saves trying to cut any sort of screw thread into the wood. The epoxy will soak into the wood enough to ensure a key on that side, and the grooving on the metal will provide a good key there, even if it is only a few thou.

Having said that, I usually do thread the outside of bushes for the boat, but only because that is a convenient way of providing a shallow groove all the way along. Once they are glued in they would never unscrew. The wood is not threaded, it is just a clearance hole, and the thread is whatever seems convenient for the size of bush. Incidently this approach is favoured instead of ordinary woodscrews in the boat because the inside screw can be removed and replaced many times without damage to the wood, and they don't conduct water inside the timber. The inside hole in hte bush is blind.

John

Scratch marks left by course emery cloth would be more than enough to hold the epoxied brass rod in a clearance hole. I would not be doing it to any instrument like that, what does the manufacturer suggest, they would be the people I would ask. Ian S C

With the greatest respect to the OP, from the original question I would surmise that you have not done anything like this before. I would strongly suggest you try this whole operation out on scrap materials and it will give you great insight as to how big an ask your original question was.

This is by no means a criticism and anyone who asks me for help will get it and if I personally don't know the answer I will try to guide them in the right direction. It is the people who don't know but go right ahead anyway who frustrate me. Bit philosophical for a Sunday morning perhaps but I am feeling all Holiday'ish today

I would not be drilling any guitars.

graham.

Just remains to thank everybody again for their most welcome and helpful advice, and to reassure Graham that the end result will be perfect. I may well be a relative novice at metal - lathe work, but when it comes to woodworking (and guitars in particular ) I go back a long, long ways ...

I don't know if it is possible to print pics in posts, (this forum software is highly individualistic) but if it is, then I will post pics of the finished article on this thread.

I will still continue to ask dumb questions ...my next imminent purchase is a mini milling machine , so I will be looking for advice on that front.

Once again. thank y'all and have a Merry Xmas .

Intrigued ... I've just had a look at Ed Claxton's site

What beautiful instruments they are !

... I hope the Amadeal Mini-Lathe doesn't panic

MichaelG.

I should probably have mentioned that I have been in regular email contact with Ed ever since I got the guitar, and I will extend him the courtesy of informing him of what I am about to do prior to actually doing it.

It is because of my high regard for his abilities as a luthier and the quality of this instrument in particular, that I am doing this in the first place. If this guitar was a Martin or a Taylor or a Lowden or a Gibson .... I would whack in a strap button into the side of the heel ...no probs.

This instrument however, is on a higher plane, and deserves better.

Edited By murrmac on 22/12/2013 19:02:16

Totally off the wall, perhaps use the normal button location, but instead of a protruding button, some sort of socket, which can be a lot shorter. The strap end could be fitted with a bespoke bayonet fitting that expands when you push a button into it to give 100% positive lock. Remove the strap and all you have is a modest, flush-finished brass-ringed hole.

Neil

(who has no compunctions about being evil to musical instruments - you should see the Hohner headless bass that my brother converted to left hand and I converted back again...)

if this instrument is on a "higher plane" it doesnt deserve a great big hole being drilled into it!!!

another place to look for inserts of all sorts is Tappex (tappex.co.uk) they have a very large selection of this sort of stuff and it looks very good when it is inserted. I have used them for high value industrial projects requiring visually perfect finishes.

Mark

Edited By murrmac on 23/12/2013 00:17:51

murrmac

I am not a Luthier, nor a Musician; but this is an interesting problem on several levels ... Thank you for bringing it to the forum.

You have, I think, addressed the Ergonomic and Cosmetic issues very cleverly. Page 3 of your Strap Buttons link illustrates the obvious difficulty and [as Mike Williams has remarked] it is a pity that the Luthiers do not make standard provision for a strap fixing of some sort.

I applaud your willingness to modify the guitar, because: However beautiful it may be, it is intended as a tool for you to make music [*]. Provided that your modifications do not alter the Tone of the instrument, or put its longevity at risk, then I see what you propose doing as a good thing [and I suggest that it might find its way into production].

I do have some reservations about the Z-bar that you mentioned earlier, but will return to that in another post.

Meanwhile, may I just ask about the Heel? ... Am I correct in assuming that the decorative (Ebony?) piece is simply glued to the structural heel of the neck? [Sorry, you can see that I'm struggling with anthropomorphic terminology here!]

MichaelG.

.

[*] Similar debates are familiar in this community ... every time someone proposes drilling a small hole in a respected Machine Tool.

Hi, and thank you, to the two Michaels above ...

@ Michael W ... yes, you are totally correct in what you say ... I have to stress that there is a difference between commissioned instruments, where the luthier is building to the player's exact specs, and what I would call "retail high end " instruments, wherein somebody like the admirable Trevor Moyle (who runs TAMCO) takes it upon himself to commission an instrument from a top flight luthier with the objective of selling it on to a customer down the line. That is where my Claxton guitar sits ...I bought it retail, already built...If I had commissioned it ab initio I would have incorporated all the specs which I am about to implement as a retro-fit..

Custom luthiers are indeed able to offer clients features which facilitate playing the instrument standing up.

First and foremost would be the so-called "Manzer wedge" which entails the body of the guitar being built with the bass side being around 1/2"( or more or less) thinner than the treble side. This doesn't sound like much, but it actually makes for a huge difference in playability, especially when standing.

The other innovative feature which many luthiers are offering is the soundboard bevel, originally the brainchild of the amazing Canadian luthier Grit Laskin, wherein the soundboard /side junction on the lower bout of the guitar, instead of being a 90 degree angle as in most guitars, has a 45 degree bevel between the top and the side, making for a much more comfortable contact between the right hand arm and the guitar.

These features however will only ever be available on custom built instruments, which mine is not..

@Michael G ...hi Michael ... I will look forward to hearing about your reservations about the Z bar , all opinions gratefully received and welcomed.

I think I see where you are coming from with the end cap thing ...you may be thinking ...remove the endcap, do your stuff ...if it all goes pear shaped then glue the endcao back on and nobody is any the wiser. And yes, the end cap is in fact ebony, glued on to the heel.

Thing is, I think it will actually look a whole lot neater to have a polished ebony end cap with a polished brass insert, than to have a mahogany triangle with a brass insert, which will inevitably end up looking like a job awaiting completion.

murrmac

Regarding the Ebony Cap ... I agree 100% ... It was more the structural integrity that I was wondering about.

You are now going for the "Grooved and Glued" arrangement, so I'm sure that 6mm is good for the rod diameter, and obviously the chosen length will greatly reduce the risk of break-out.

Now that the 6mm is not externally threaded; it may be worth increasing the screw diameter slightly to (say) 4.5mm for added strength and I would strongly suggest that you use something with a length of plain shank [i.e. a Bolt not a Screw], and counterbore the rod to accept this. ... If I have understood your Z-bar idea correctly, then there is a risk of putting unwelcome loads onto the screw, and I think it wise to do everything that you can to reduce the risk of the screw snapping like the proverbial Carrot.

If it was me [which of course it is not]; I would mould an "Over-Shoe" for the heel, preferably in Epoxy/Carbon. ... this would be attached by bolting through the end, just as you propose for the Z-bar. The three-dimensional shape should make it inherently stiff, and of course; by enveloping the heel it is protected from side-loads. The moulding would incorporate whatever fixing is chosen for the strap, and it could be lined with Chamois Leather to protect the finish of the heel.

... Alternatively, the same idea could be executed as a Lost Wax Casting.

What do you think ?

MichaelG.