Drilling into the body?

[Matt Liebenau]

Lots of good advice above. If I was doing this in my shop I’d:

Tape up the area to be drilled with painters tape, use a center punch to mark exactly where you want the hole, drill all the way through from the front with an 1/8” bit, use a Forstner the correct size (3/8”?) and start at the front, run it backwards enough to to score the tape and finish, drill about half way through from the front obviously using the 1/8” hole as a pilot for all this then drill the rest of the way from the inside.

The other option if you don’t already have Forstner bits and don’t want to buy one (they’re not that expensive) would be to do the whole thing above with a good brad point. They’re typically a little less and as long as you have one with cutting spurs on the edges it will score the finish as well and help with tear out.

When it comes time to remove the tape peel it all around the edges towards the hole you just drilled then seal the fresh edges, carefully, with a couple of drops of CA glue. Let it dry then install the new pot.

 

[H K]

Masking tape on top always works for me.

 

[bherman]

I'm a serious woodworker, agree with others on Forstner bit. If its only 3/8" it will not cost much (less than $10), the most important thing is that it is sharp. So if you don't already have one, a new one from Home Depot or your local hardware store will do. No need for carbide bit, this is a simple process. A plain old battery drill will be fine, just take it slow. Some painters tape over the area you're drilling is a good idea. Also, have a vacuum handy and keep the area clea as you go - youdon't want sawdust getting into the electronics once your hole goes through.

 

[ragetoca]

Measure 2 or 3 times. Drill once
Make sure they new hole is aligned and placed evenly

 

[fhm555]

• Painter's tape over the area to reduce paint chipping.
• Center punch to get a starting point.
• Very small pilot hole.
• Use a brad-point bit to get a clean score of the outer edge.
• Start on the painted side.
• Ensure the bit is straight so it cuts the circumference equally all the way around.
• Don't force the fit too fast. If it digs in too quickly it can tear the surface.
• To reduce tear-out inside, you could drill 1/2 way then flip the body over and drill the other 1/2 from the inside.

A drill press is great for adding control and precision to something like this but it can easily be done with a hand drill too. I have many times.

I'd be careful with a center punch. I've cracked a thick poly finish using a center punch before drilling. In my case, I was lucky the crack was smaller than the diameter of the hole, but just by a little.

 

[Turnaround]

I've read some how-to's that say to run the bit backwards, with light pressure, to score the spot you're drilling. Then, supposedly, it's less likely to chip the finish when you drill through the right way.

I've never done it, so can't speak to the effectiveness. Can anyone confirm?

Standard practice for me. I run it backwards very slowly at first to score the finish using a lipped bradpoint bit. Then slowly in the right direction until I am through the finish, then up to speed. If you can't clamp a wood block to the inside of the hole, best stop half-way through and finish it from the back side.

 

[ctmullins]

Bow and arrow from between 13 and 15 meters. Carbon shaft with a Tusq tip. Compound bow, preferably at 35lb or higher.

Report back.

 

[Plain Old Barry]

I agree, but I'd take a mediocre Forstner over even the best twist drill for this job.

The Lee Valley sharpened ground tip brad points are AMAZEBALLS in hardwoods. Not grandma's twist drill. I've completely switched to them from forstners under 3/4", as they're far better at clearing chips and the cut quality is superb. They will actually cut you if you touch the tips or edges, they're that sharp.

Try one sometime.

 

[rojo412]

Taping the area is always advised.
Brad, Forstner, or stepped bits are always a win for me.
And if you have access to a drill press, carefully and slowly pressing down the bit does wonders to avoid chipping with any of the bit styles listed above.

 

[tubatodd]

OP Here. It is time to drill that hole. I thought of various ways of how to calculate where the 4th hole should go. I even discussed this at breakfast with my wife. We did some back-of-an-envelope sketches. A ruler and protractor seems like the best way to calculate the measurements. I thought of a way to do it without actually measuring.

Step 1: Put tape where the new hole will go.

Step 2: Lay tape across existing holes and punch thru the holes

Step 3: Move the tape to where holes 1 and 2 of the tape, line up with holes 2 and 3 of the bass.
Where the 3rd tape hole lays, is where the 4th hole goes.

I am going to take measurements to make sure this is the proper alignment. How would you calculate this placement of the 4th hole? I confirmed that the hole placement does align with space in the cavity.

Any reason I shouldn't calculate it like this?

 

[ctmullins]

That’s a great idea! As long as there is room in the cavity, it’ll work out great!

 

[tubatodd]

That’s a great idea! As long as there is room in the cavity, it’ll work out great!

This Sterling by Music Man SB4 appears to be an exact copy in every way to the Ernie Ball Music Man Sterling, except that the 4th hole isn't drilled. The cavity has the space for the 4th pot to reside.

 

[Matt Liebenau]

OP Here. It is time to drill that hole. I thought of various ways of how to calculate where the 4th hole should go. I even discussed this at breakfast with my wife. We did some back-of-an-envelope sketches. A ruler and protractor seems like the best way to calculate the measurements. I thought of a way to do it without actually measuring.

Step 1: Put tape where the new hole will go.
View attachment 7223188

Step 2: Lay tape across existing holes and punch thru the holes
View attachment 7223189

Step 3: Move the tape to where holes 1 and 2 of the tape, line up with holes 2 and 3 of the bass.
Where the 3rd tape hole lays, is where the 4th hole goes.
View attachment 7223190

I am going to take measurements to make sure this is the proper alignment. How would you calculate this placement of the 4th hole? I confirmed that the hole placement does align with space in the cavity.

Any reason I shouldn't calculate it like this?

That absolutely works and keeps everything relatively symmetrical. The only concern would be if the extra hole actually hits the cavity and that there’s room for a potentiometer and you said it does and there is so… Wha’ could possibly go wrong?

 

[Plain Old Barry]

OP Here. It is time to drill that hole. I thought of various ways of how to calculate where the 4th hole should go. I even discussed this at breakfast with my wife. We did some back-of-an-envelope sketches. A ruler and protractor seems like the best way to calculate the measurements. I thought of a way to do it without actually measuring.

Step 1: Put tape where the new hole will go.
View attachment 7223188

Step 2: Lay tape across existing holes and punch thru the holes
View attachment 7223189

Step 3: Move the tape to where holes 1 and 2 of the tape, line up with holes 2 and 3 of the bass.
Where the 3rd tape hole lays, is where the 4th hole goes.
View attachment 7223190

I am going to take measurements to make sure this is the proper alignment. How would you calculate this placement of the 4th hole? I confirmed that the hole placement does align with space in the cavity.

Any reason I shouldn't calculate it like this?

Using dividers to step off equal distances is a time honored method. A compass can act like dividers.

 

[tubatodd]

Take 2:

This time I busted out the protractor. In my 20s, I was a both a high school geometry teacher and assistant band director. That was 18+ years ago. If I didn't try to do this mathematically I guess might have felt my positioning was not precise.

First:
I measured the distance of the adjacent holes from their centers, with the protractor. I then made an arc from the center of the last hole to where the new hole would be going. I used painters tape to center the pointy end of the protractor.

Second:
I measured from the center of the first hole to the center of the third hole. I then made an arc from the second hole, to where the 4th hole will be going.

Modus ponens!!!!

The intersection of those 2 arcs should be the exact point where the new hole will go. Now I have to measure twice more and drill.

 

[ctmullins]

Nerd

 

[Matt Liebenau]

Nerd

He means it in a good way! I swear.

 

[tubatodd]

Well the nerd was wrong.

I measured many times prior to drilling a tiny pilot hole only to find the new hole's center is too close to the wall of the cavity. Doh!

I was wrong in saying this was exactly like an Ernie ball Sterling. I have an American Sterling and I probably should have taken measurements off of it. Duh! The arrangement of knobs on the Ernie Ball is not perfectly symmetrical. That red line is the difference. The distance between 1-3 and 2-4 are 3mm different.

What I did do right was making a tiny pilot hole. I adjusted the new hole placement so that it's not so close to the wall, but puts that tiny pilot hole as the far edge of the hole.

What I did wrong, was not buy a 5/16" fortner bit. The 1/4" is too small and the 3/8" is too big.

Did I ruin this bass? Of course not. The adjusted hole placement does fit the pot with a bit of wiggle room.

More pictures to follow.

 

[tubatodd]

Based on my measurements of the Ernie Ball, I suspect the arrangement of knobs is closer to the outer wrap of a golden spiral or a Fibonacci spiral.

 

[tubatodd]

All done!! Yey! I bought a set of regular drill bits which included the 5/16" that I needed. Unfortunately, it did result in minor chipping. If I were to do this over again, I would make sure I have a 5/16" Forstners bit from the start. This photo lookks worse than it is.

Pictures of the soldering and installation of the 3-band preamp.

Soldered ready to test. Heat shrink installed, but not in place or heated yet. Had to play test first.

Heat shrink in place and shrunk.

Ready to close up. I put a piece of electrical tape across the white connectors so make sure nothing creates an unintended ground.

Everything buttoned up. The washer and nut hide the bit of chipping. Not a bad job for a rank amateur like myself.

Now I need to order a set of similar knobs with a set screw as these pots are smooth. Overall the upgrade turned out GREAT! The preamp sounds awesome, even if it is just a stock Cort preamp.