Marking for Accurate Tuner Hole Placement

[crazymandolinist]

Hey everyone, I know a lot of you use a tuner drilling jig for your headstocks to get clean, accurate placement for maximum smoothness but I'm more interested in just marking it out accurately by hand. What are your methods of doing this? How do you measure for the hole placement and proper spacing? Some pictures would be much appreciated.

Thanks,

Ian

[sunburst]

-On a scrap and on the peghead, scribe a straight line where the tuners are to line up.
-On the scrap and on the peghead, center punch a point on the scribed line for the first tuner post.
-On the scrap and on the peghead, measure with an accurate caliper and center punch the last tuner post on the scribed line.
-Set a divider to the distance between tuner posts, measured any way you can.
-On the scrap, "walk" the divider from the first punched point to the last, right on the scribed line and see if it ends up exactly at the last punched point, if it doesn't, adjust it until it does.
-When the divider is accurately set, walk it on the scribed line on the peghead and punch each point where it touches. These are accurtely measured tuner post positions.
-Using a pin vise, drill very small holes at each punched point at 90 degrees to the surface, all the way through. (A pin vise can be mounted in a drill press for drilling through, but starting the holes by hand with a magnifier is a good idea.
-Using a high quality brad point drill bit of the correct size for the tuner bushings you want to use, drill the holes in the peghead. The center spur of a high quality brad point bit will be exactly in the center, and it will follow the pilot hole and guide the bit for accurately spaced tuner holes.

This is how I made my drill jig, and it is so accurate that I can install bushings in holes drilled with it, and a set of tuners will drop in or out using only gravity. If there is interference, it means the tuner plates are not straight.

[Michael Lewis]

A method I have used is to remove the spur gears and string posts from the set of machines and mount the base plates securely to the back of the headstock. Using a transfer punch mark each string post hole. For those of you who don't know what a transfer punch is, they are usually sold in sets of gauged sizes like a set of drills, but they are center punches. You select the size that fits into the hole of the base plate and press it into the wood. This way you get the actual position of the string post. Then you remove the base plate, re-assemble the machines, and drill the headstock always striving to maintain accuracy.

[Tavy]

Ian - I made up an SVG file with the tuner spacings marked out - printed out to scale (from Inkscale) you can tack onto the work surface with double-sided tape and then centre-punch and drill as per Spruces instructions. Practice on scrap first, and check the tuners drop in under gravity as spruce says, depending on your printer you may need to adjust the scale at which it's printed out very slightly... Ah wait I have a PDF which I'll attach here - the ruler line on the top of template should be exactly 15cm if memory serves which lets you calibrate your printer...

[sunburst]

Michael, I've heard of that method, but I would first want to double check the tuner plate for accuracy. The method is limited by the accuracy of the tuner manufacturer, and depending on the brand, bending the plate can throw off the accuracy of the holes, I know this because I've had tuners bent in shipping, or in manufacturing, or at some time before I got them, and they did not correctly fit the holes drilled with my jig after straightening. Now, if you use the very tuner plate that will be installed, and if it has slightly "off" holes, then you have a near perfect fit... until the owner decides to change the tuners, tailpiece, and bridge... you know how folks are.

Tavy, thanks for the PDF. I'll use that when drawing pegheads in the computer!

[crazymandolinist]

Thanks guys this really helps!

[kkmm]

Thanks for the template

[j. condino]

Accurate tuning machine holes are incredibly important for mandolins and difficult to achieve.This simple, affordable tool is easily worth ten times the asking price:

https://www.stewmac.com/Luthier_Tool...Drill_Jig.html

[HoGo]

I do much like John, but since most tuners are metric 23mm post spacing I just mark the placement using standard ruler on front of headstock. I use awl to mark deeply the locations and drill with forstner drill in drillpress without any predrilling. Once the drill tip catches the awl punch it will follow down and drill press will drill square. Gravity test is what I do as well.