Quick Repair Tip: Careful when enlarging existing endpin hole to pickup endjack hole

[vintageparlors]

Adding a pickup to your acoustic guitar isn't that hard to do. There are many pickup options out there to consider but many brands share specs for the opening size hole at the end block to insert and secure the end jack. The pickup most requested in the shop by old parlor guitar lovers is the K&K Pure Mini, which calls for a 1/2" hole drilled to accommodate their end jack. Today's tip isn't about installing the K&K pickup but rather a caution when enlarging an existing (smaller) endpin hole to accommodate a new (larger) end jack hole.

This old Harmony flattop has the typical white plastic endpin inserted in a 1/4" tapered hole in the end block. Once you remove the old endpin you can see how much smaller the existing hole is compared to the 1/2" brad point bit I use so the new end jack will fit.

If I were to insert the 1/2" brad point bit into the existing 1/4" hole and try to drill it for the new end jack, that bit would dance around in circle, flopping about, and make an awful mess of what should have been a nice clean 1/2" hole. The reason is that the bit has no solid point of entry, or purchase, for it to center and proceed into wood under control.

By gluing a wooden dowel into the exiting endpin hole, I can create a solid and controlled point of entry, resulting in a nice clean 1/2" hole. There are other approaches to this, I'm sure, but this approach works fine for me.

No matter what approach you might take or what kind of drill bit you use make sure it is nice and sharp and always put masking tape over the center of the hole you're drilling before you drill to help to reduce tear out.

I wasn't smart enough to figure this out years ago but I've never forgotten about doing this extra step before enlarging an exiting endpin hole. It only took one time to see the god-awful mess it makes, this I know.

[Rudy4]

I do it the same way, except I advise using a Forstner bit. The Forstner bit has the huge advantage of being self-guiding once it starts cutting.

Twin flute bits of any type are always dicey for this type of work.

[E-OM]

Been there and had the mess...

Thanks for a good tip...

[mirwa]

Sorry definetley dis-agree, use a reamer, anything that has a high rake such as a brad bit has a high rate of potential damage to the finish and body.

[Fathand]

Brad point bits are great for creating new holes accurately in the right place, Forster bit too with nice flat bottoms but neither is good for enlarging an existing hole.

The common twist drill is lazy and likes to follow the path of least resistance, it should be your drill of choice for enlarging existing holes. Increase the size in stages for better accuracy.

[vintageparlors]

Thanks to everyone for contributing other options to my approach. More approaches invite more options, which will give those learning the craft more ways to consider dealing with this task and that's a good thing.

[Rudy4]

Originally Posted by Fathand

Brad point bits are great for creating new holes accurately in the right place, Forster bit too with nice flat bottoms but neither is good for enlarging an existing hole.

The common twist drill is lazy and likes to follow the path of least resistance, it should be your drill of choice for enlarging existing holes. Increase the size in stages for better accuracy.

Vintageparlors has that covered with gluing in the scrap of dowel. Any type of center guided bit then is essentially drilling in "new wood". The secret is to remove the existing hole.

The Forstner bit is center-guided for starting the bore and then is self-guiding by nature once it starts a bore.

As pointed out earlier, the twin flute drill bit will pull itself aggressively into the wood, often with collateral damage at the hole's edge (i.e. your guitar's finish) and tear out when the bit exits the bottom of the hole.

If there's any doubt before enlarging the hole in your possibly expensive instrument it's easy enough to test both in a scrap of wood.

I've installed several end pin jacks and I know which type I'd use. After gluing in the dowel scrap and covering the surface with wide masking tape the Forstner cuts a clean edged hole as it starts boring, self-centers as it creates the new hole, and does minimal or no damage when it exits the bottom of the hole.

A reamer is also OK to use but I don't like to use them because they can exert unneccessary force on the top edge of the hole which can result in lifting or cracking the finish depending on what has been used.

[IndianHillMike]

I like to do it the same way as vintageparlors but will add that it can be useful to slowly run the brad point bit in reverse at first to score the finish and outer wood before drilling -- that's usually all you need to prevent chipping, etc.