K&K Twin in an oval-hole

[CelticDude]

I put a K&K mandolin twin internal into a Collings MT, and found it wasn't that hard to position the 2 pickups. However, as I think about doing the same for my MT-O, it doesn't seem as easy. I would guess that the 2 pickups go in approximately the same place - under the feet of the bridge. But getting them there, through the oval sound hole and around the x-brace, seems like a challenge. Does anyone have experience doing this?

Also, I used a TapaStrings endpin last time, but am thinking about drilling out the end this time. Drilling the wood, while slightly nerve-wracking doesn't seem hard, but the hole in the metal tailpiece would have to be enlarged as well, and this seems tricky to do neatly. Again, has anyone done this?

Or should I follow the advice of the great philosopher Clint Eastwood, and know my limitations, and get a luthier to do this?

[pops1]

If it were me I would take the tailpiece off to drill it. Place it on a piece of wood and enlarge one bit at a time. I would make a jig for mounting the pickups, that could be a clamp with the inside part built up to clear the brace and still contact the top. The locator would be the top of the clamp so you know where you are. An Ibex bridge clamp would be a good choice.

[jim simpson]

I drilled a mandolin once to install an endpin jack. I botched it a bit as the jack didn't seat evenly. I should have used a reamer that would have given a more controlled cut.

[Mandobart]

Often asked question, and I have often answered it. Here are cut n' pastes from my previous, with some links as well.

This thread (http://www.mandolincafe.com/forum/showthread.php?81854-K-amp-K-internal-pickup), about 7 posts down is my explanation on how I've done this a variety of ways. Also, if your using the switchjack (http://www.stewmac.com/shop/Electronics,_pickups/Components:_Jacks/Switchjack_Endpin_Jack.html?actn=100101&xst=3&xsr=5452) it is not necessary to take it in and out a bunch of times, follow the advice on this video (http://www.youtube.com/watch?v=xSNvuz9WNQE), especially at ~ 3:20 for setting the correct length for your tail block. I'll repeat here that using blue tack to mount the p'ups under the soundboard has worked great here on many instruments from fiddle to upright bass. I use a thin (about 0.5 mm) pad of putty. Its been holding over eight years now on my old mando, yet it is easy to remove if you want to try different locations. I use a step drill bit to carefully enlarge brass tailpiece holes (with tailpiece removed, of course) and a brad point bit to drill out the wood. As always, I'll plug my favorite JJB pickups (http://www.jjb-electronics.com/PPS-200.html) (NFI). They work just as well as K&K (I've tried both) for much less cost.

For drilling, If its a real tapered endpin and there is a through hole, use a reamer. Size depends on the jack you're using. If you need to enlarge the brass tailpiece, use a stepless drill bit (http://m.harborfreight.com/3-piece-stepless-drill-bits-66463.html?utm_referrer=direct%2Fnot%20provided). ALWAYS remove the tailpiece before you attempt to drill it. ALWAYS clamp it securely and don't try to hold it with your soon to be missing fingers while drilling! If you have a screwed in strap button instead of an endpin use a brad point drill bit through the tailblock. Again, size depends on the jack you're using.

This thread (http://www.mandolincafe.com/forum/showthread.php?112227-1-4-quot-Jack-Options) shows ways I have installed the output jack.

For working inside the instrument, I use an S-type soundpost setter (http://www.stewmac.com/Luthier_Tools/Tools_by_Job/Tools_for_Violins/Soundpost_Setters.html) to get inside and mount the heads. Its important to cover the shaft of the tool with electrical tape or heat-shrink to protect the instrument. Also, I always put low tack painter's masking tape (blue kind) along the edge of the sound hole(s) to protect them before poking around. I also tape the bridge in place before removing the strings and tailpiece. I always mount the heads as close as internal bracing will allow to directly under the bridge feet contact points.

I've used the above tools and methods now to install internal twin head pickups in an f-hole and oval hole mandolin, an f-hole (tone bars) and an oval hole (x-braced) octave mandolin, an oval hole mandola with x-bracing, an f-hole and oval hole mandocello, two violas, a violin, three guitars, a banjo, and an upright bass.

I'm not going into soldering - if you can do this consistently well without frying components, you know the difference between an iron and a gun and you understand how to tin and prepare joints, and know how to use heat shrink and RTV then you're good to go. I was an electronics tech in the USN for 9 years.

In most cases this is a two hour or less job including clean up after. I don't know what a luthier in your area would charge, and I've never done this for money. But I would be surprised for the labor to run much more than $150 USD.

[almeriastrings]

+1 on Mandobart's instructions. Many years ago someone came to me with a mandolin with a cast tailpiece that they had tried to drill while still on the mandolin... it grabbed.... the mando tried to revolve with with the drill bit. You can imagine the rest :(

[CelticDude]

Okay, thanks. It's take a few reads to absorb all of Mandobart's advice. When you say a reamer, I think of a handtool used on violin tuning pegs. Is there an electric version? I did get a special bit from Stew-Mac for installing K&K's in a guitar; I may be able to use that. And yes, it never seemed like a good idea to leave the metal tailpiece on while drilling.

[Mandobart]

Yes I use a T-handle hand turned reamer, not a reamer bit in a powered drill.

[CelticDude]

Mandobart: Thanks for your input. Just to clarify a few things:

In the 2nd paragraph above you say, "I use a step drill bit to carefully enlarge brass tailpiece holes (with tailpiece removed, of course) and a brad point bit to drill out the wood". But in the 3rd paragraph you say, " If you need to enlarge the brass tailpiece, use a stepless drill bit. ALWAYS remove the tailpiece before you attempt to drill it" Is one of these a typo, or am I missing something.

Also, I was surprised at how expensive hand reamers are. They also only appear to create a tapered hole, whereas the Stew-Mac reamer bit goes to either a straight 15/32" and then straight 1/2". So if I do go for a hand reamer, what exactly do I want?

The S-setter looks good, as I was thinking I'd have to come up with something on my own. Still seems like a guess as to where the bridge feet are from underneath, but I figure I can "measure" with the setter on the outside, and then mark it, and then just guess the distance from the middle. Good ideas about covering with tape to not damage anything.

Yes soldering is no big deal. I've done enough radio project, plus the Tapastring jack on an MT, that I know to use a soldering iron, and which end gets hot. For the MT, the big deal was how amazingly thin the wire coming from the pickups is, so stripping it was a bit tricky.

[Mandobart]

Yes a step-less bit, like the harbor fright item in the link - not a stepped bit. I have the special violin reamer for pegbox work, but I also have a plumbing reamer for deburring the ID of cut pipe; works fine. I never measured the taper on it. It goes up to 1/2". Stewmac stuff is good but priced higher than other places like international violin, Decor music, shar, etc. I use the sound post setter and a small inspection mirror to place the p'up heads.