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Can some one give me an idea of what sort on tail-block depth maximum to accommodate retrofitting of a jack-plug in case an owner wants to fit a pick-up later?

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I use 1/2" Baltic birch plywood for my tail blocks. With that and the side thickness it doesn't max out the thread on the DTAR end pin. But I wouldn't want to get much thicker.

Colin:
I use the LMI EBJB end pin jack for every build, just so someone else can't mess up with a DIY installation. I just checked a tailblock in an ongoing build and that's .830" thick including side thickness and I know for sure the jack will fit. These jacks look first class also.
Tom

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A person who has never made a mistake has never made anything!!!

On my last guitar, I installed a K&K pickup, which comes wired to an end pin jack like the LMI EBJB jack above. I discovered that the 1" thick tail blocks I was using were too thick by about 1/4" so it took some creative use of a stepped reamer from the inside to make it possible to install the jack.

On my next guitar, I'm going to give one of these threaded end pin jacks sold by StewMac and WD Music Products a try. Since it doesn't require an internal nut, the thickness of the block doesn't matter. It should also make the installation of the jack simpler because you wouldn't have to mess with getting the internal nut adjusted to just the right position on the jack barrel so that the external end is precisely located just proud of the outside surface to avoid damaging the finish when tightening the external nut. It's also nice that there's no internal nut to come loose down the road. You do have to tap threads for this jack but that should be easy enough. The slot in the external face makes it a little less attractive than the LMI jack, but how many guitar players sit around gazing at their end pin jack? Not me.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

I use a 9/16 tailblock and have had no problem.

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Blue Ring Acoustics
blueringacoustics.ca

Don't know who's to blame for starting this incorrect notion that end pin jacks should be drilled out with a 1/2" bit and I suspect that it was the pup producers but it's wrong.... R - O - N - G! It likely was the pup manufacturers knowing as they will that if their stuff requires unnatural acts to install folks won't buy it. Lots of folks will have a 1/2" bit but maybe not as many will have the correct.... 15/32" bit.

The most common cause of jacks coming loose and they come loose very frequently is that incorrect 1/2" hole.

See this: https://www.facebook.com/a2guitars/photos/ms.c.eJw9zMENwDAIQ9GNKjsEMPsv1jQkPT592aQFEPRJS~_BhuwYE8zrO8fXQ72j7sbrn7eq9XZcp57pnm~_DuI69j9SjpmL7~;Zrzn2h~_~;.bps.a.113600518747043.19651.100681526705609/113600615413700/?type=3&theater

Wouldn't a couple wraps of tape snug up the fit?

We've gone to 12mm Baltic Birch for most tail blocks.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Sure but it's easier to simply drill the hole in the first place with a 15/32nd" bit.

If you check out the photo-toot that I posted a link to (there is a series of photos with the "next" button near the top, right side of the first pic) there is another gem in the toot.

How folks snug up the jack too and how it was intended to work are often very different things.... All day long guitars cross my bench and one of my "staple" tools for things that I address is Frank Ford's Jack The Gripper. Every input jack be it an electric or an acoustic gets snugged up. Notice I didn't say "checked" because my reality is that jacks are always loose or very nearly always loose regardless of what kind of guitar it is.

If you put them in right in the first place as per the toot they don't come loose and we also see our own work now years later and I can attest that 1) the smaller hole size, and 2) how we snug the jack up is a more reliable over time way to install a jack.

Colin Guild guitars and a few others often have tail blocks that are too thick for a standard jack so we made a reverse counter bore tool that cuts on the pull stroke from outside the guitar. It's a hassle but we are tooled up for it....

Input jacks are pretty important to get right because often the sorts who depend on them are playing out. With this said a jack problem can be a show stopper and that makes it pretty important to get it right.

Of course, I am all about doing it right -- right from the start -- but the suggestion is for what seems to me is a simple repair or alternative for those that really don't want the expense of the odd 15/32 drill. Sleeves and bushings are used all the time in precision assemblies. And actually to prevent tear out I use a Forsner bit, I suppose a brad point would be good too -- are those available in 15/32" I admit I have not read the tutor.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Actually I misspoke in that I would not recommend drilling a 15/32nd" hole at all and instead favor the use of a quality reamer like the SM one that we use that has flats at 15/32nd. Reaming is likely safer for the instrument than a big, ole honking drill bit regardless of brad point or conventional.

As much as some here don't like hearing it Stew-mac hit it out of the park with their end jack reamer. It's exactly what the tool to do this should be in all respects except, of course, it's not free.... or cheap.... but good tools matter.

Ken my friend you are not going to like my answer about finding a work-around to doing it with a 15/32 reamer in the first place. If I had to explain to a paying client that we split their tail block trying to drill a 1/2" hole for what should be a 20 minute quick and easy pup install neither the client or we would be very happy. As such this is the business that we choose to be in and with that choice comes some costs.... an understatement. Any Luthier who damages the valuable personal property of others because at the end of the day someone was too cheap to tool-up for the work that they claim to be proficient at is not going to make very many friends in the process... This is NOT directed at you or anyone specifically.

But let's face it guitar building (and repair) has many, many costs associated with it including perhaps even thousands of bucks just to manage and measure RH before that first board ever gets cut. On the repair side it's no different and in some ways more expensive because we have to be tooled-up to repair what ever comes though the door while builders can self-limit what they want to create if they wish.

With this said I can't really participate in advocating a method or non-use-of-proper-tools because I very much understand what value the right tool brings to our table every single day.

By the way repair guys endlessly toiling at our benches with sharp chisel in hand tend to have some rather hysterical conversations as one is ripping off a neck and the other is filling a nut slot. Some of these conversations invariably center around things that we find in guitars. Last Friday Dave found a dollar and no I didn't take it either..... I once found a ole, green, toe nail covered with fungus that was being used as a saddle shim.

If we found electrical tape wrapped around a loose end jack we would be using some colorful language too I am sure and wondering who the cheap bastage that built the thing was taking thousands from a well intending client and resorting to electrical tape.... At least it's not as gross as the toe nail but when we do have a clear path forward to quality work why not just do what it takes to do it right?

I'm chuckling here because my first Stew-Mac kit cost something like $400 and until I opened the box I had no idea that I also needed $20,000 in tools to complete the thing..... Of course YMMV and mine did too but again why not do it right the first time or someone is invariably going to joke about is that electrical tape "tone tape..."

By the way last week we had a client, I say had... who was concerned that a loose clip managing his pup wires was going to dramatically change the tone of his guitar...... Before that he was concerned that the placement of the battery bag was robbing tone....

Can you imagine the heart attack he would have if he ever knew or found electrical tape sucking the life and tone out of his lousy guitar....

I guess some of us Industrial Engineers are sometimes shameless, certainly only my (non-repair person) opinion -- but I see zero harm caused by a bushing/sleeve/shim in this or any other application. Unless I told somebody they would not even know it was used. Not wanting to start an argument or get a blessing just offering up the option -- ie. I don't think its practical to "un-drill" an over-size jack hole.

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Ken Cierp

http://www.kennethmichaelguitars.com/

No problem Ken and I'm not wanting to argue with you at all, ever, either.

My concerns about the 1/2" hole when a 1/2" hole is not necessary is that pups get changed out in time too and often are not the only pup that a well constructed guitar will have in it's life span. After you and I are long gone someone will want to install the latest and greatest bluetooth with GPS and RFID pup.... and may not know to continue the tape convention......

Or in other words no problem.....

Anyone want an old toe nail for a saddle shim, I saved it....