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

[murrmacParticipant @murrmac]

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

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Rubber faced clamp – just grip the neck brace either side . Attach what you want to clamp .

[Robert DoddsParticipant @robertdodds43397]

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

[murrmacParticipant @murrmac]

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.

[julian atkinsParticipant @julianatkins58923]

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

[John OlsenParticipant @johnolsen79199]

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

[Ian S CParticipant @iansc]

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

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

I wouldn’t do it either – shoe lace or clamp on fitting for me .

MikeW

[Oompa LumpaParticipant @oompalumpa34302]

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.

[murrmacParticipant @murrmac]

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 .

[Michael GilliganParticipant @michaelgilligan61133]

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.

[murrmacParticipant @murrmac]

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

[Sub MandrelParticipant @submandrel]

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…)

[julian atkinsParticipant @julianatkins58923]

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

[Mark CParticipant @markc]

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

[murrmacParticipant @murrmac]

Posted by julian atkins on 22/12/2013 21:20:05:

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

Hi Julian …it won't have a "great big hole" drilled into it …it will have a discreet 6mm hole drilled into it which will be invisible to the casual observer, but which will enhance the functionality of the instrument by 100%.

I appreciate that your daughter is horrified by the prospect, but she plays sitting down …I play standing up, and a functional guitar strap is a sine qua non.

It is precisely because the instrument is on a higher plane that I do not want to deface it by drilling a "great big hole " into the side of the neck heel, where it would be visible to one and all.

EDIT: if you want the full skinny on strap button installation check out this http://www.frets.com/FretsPages/Musician/GenSetup/StrapButton/strapbutton1.html on Frank Ford's site.

Frank is the undisputed  doyen of guitar repair and customisation, and everything he says is the voice of experience.

Unfortunately, he doesn't cover the situation whereby a player wants  the balance of a side mounted strap button, but  doesn't want to desecrate a really high end instrument by doing this.

Which brings us back to square 1 …     

 

 

 

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

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Just some random thoughts for general interest :

I can see lots of ways that a guitar would need to be adapted so as to be easy to play standing up rather than in the classic sitting position .

The answer though lies in a different place to adapting an existing ‘standard’ design guitar – a guitar to play standing up should be purpose designed from the beginning with some original thinking as to design details .

Further the design should have shape and measurement details to suit one specific player .

This sort of thing is actually quite common practice at the high end of bespoke manufacture of speciality goods for discerning customers .

Bespoke fitting to customer requirements reached a high art in two surprisingly different spheres – quality shot guns and top hats ! There are though many other examples .

Regards ,

MikeW

Edited By MICHAEL WILLIAMS on 23/12/2013 09:14:37

[Michael GilliganParticipant @michaelgilligan61133]

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.

[murrmacParticipant @murrmac]

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.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by murrmac on 23/12/2013 15:59:45:

@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.

[jason udallParticipant @jasonudall57142]

As posted ..the challenge of drilling and tapping M6 brass..M4
Has been done.

As to the original purpose of the part.

Maybe the helicoil I suggested earlier is still a goid idea..If you are willing to drill the instrument.
I would drill the tap size for helicoil. .and counter bore. Thus completely burying the helicoil..and taking the lateral loads straight into the mahogany. .use a “bolt” as M. G..suggests. .plain under the head and the threaded portion of reduced ( to M4 say) size
In effect a dowel pin retained by insert

A better ( no change to accoustics possible) idea is again M G above
.fabricate a “claw” for the bit of instrument to engage with.
For this I suggest ” fantastic plastic”..
Thermoplastic at 60?C and tough and springy when cool..used for orthopedic splints. .warm with hot water and mould over mating part. ..not sticky completely clean. .and smooth able while warm..if shape doesn’t agree simply try again. ..
Also colour tints available. .so could be tinted to suit …

[murrmacParticipant @murrmac]

You guys are just amazing …seriously amazing …

@Jason, your idea re thermoplastic sounds good …(I have no experience of thermoplastic but I am very willing to learn) …helicoil ?? maybe not … I want to preserve a "clean " look when the mounting is disassembled (which will be most of the time) and I think a helicoil would not give that look (although I could always design a discreet capping which would conceal it ) but your thermoplastic idea is something which I will seriously investigate …and thank you again for an excellent suggestion.

@ Michael G …Michael I bow down … I am not worthy …

Your suggestion is absolute genius … and is indeed the way I will proceed. You say you are not a musician or a luthier, (which I don't believe for one minute) but you have nonetheless come up with absolutely the ideal way to negate the unwanted stresses on a delicate neck heel … I am left thinking "Why didn't I think of that ?"

Now …in view of the fact that the load will now be shared on the opposite side of the neck , I would assume that your proposal that the internal thread should be increased to 4,5 is no longer an issue?

In fact, if the stress is being taken up on the opposing side of the neck heel …then all that is required is a fixing which will hold the "cradle " in place ..in theory I could go down to M2 …and fabricate a 4mm OD brass insert ? …although realistically I wouldn't go lower than M3.

Once again, thanks to you and to Jason for providing the last links in the solution …and thanks to everybody else who has contributed to the thread. It has certainly been a learning experience for me.

 

 

Edited By murrmac on 23/12/2013 18:37:51

[murrmacParticipant @murrmac]

Ok …once again thanks to all contributors …I would never have got this level of insight on any of the normal luthiery forums.

So this is what is going to happen I will trace the outline of the Claxton neck heel and give it to my friend Pat at Waterjet Scotland ..he will then cut out the profile on his waterjet machine out of 1/2" thick aluminum plate.

I will then drill the holes for the M4 bolt and for the strap clip, in the correct place, and will clad the rest of the "cradle" in black heat shrink sleeving to avoid damaging the guitar finish.

Pictures will be posted after all this is accomplished.

Just to reaffirm …this will still involve drilling a hole in the neck heel …no way around that …but it won't be quite as invasive as I had first envisaged.

[Ed DuffnerParticipant @edduffner79357]

To add or retain to the aesthetics of the un-mounted strap bracket, perhaps you could inset your threaded insert below the surface of the heal cap. i.e. give the wood a counter bore, so it could accept an ebony plug with maybe a slot for insertion/extraction? …similar to the button battery compartment on a camera. Or maybe make it from a metal that matches your guitar hardware, and perhaps a matching thread in the ally bracket so you'll have somewhere to put the plug when it's removed.

Sorry for the rambling, I've eaten loads of sugar today.

Edited By Ed Duffner on 23/12/2013 20:30:05

[murrmacParticipant @murrmac]

Hi Ed …yes, the intention always was to sink the insert underneath the level of the heel cap so that in the worst case scenario I could fill the depression with black CA and polish the heel cap back to pristine perfection.

Even as it stands, my OCD will compel me to machine up a ( removable) discreet cover for the brass insert …

[Author]

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